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MICHAEL SHORT: All right, guys.

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Welcome to the last
official day of 22.01.

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Can't believe we've
actually made it here.

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And you guys have
learned a ton about how

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ionizing radiation
does and doesn't affect

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different types of matter.

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If you've noticed that
the whole class has

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been kind of taking a slant
towards looking at issues

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00:00:39,360 --> 00:00:42,000
in the public sphere
from things like hormesis

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to dose, to risk,
to power plants,

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today we're going to talk
about food irradiation.

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One of the main
reasons that we have

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all sorts of incredibly
safe food today

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thanks to ionizing
radiation, a lot of the myths

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and misconceptions and
science behind what does

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and what doesn't happen
when you irradiate food.

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And you guys are fully
equipped to determine

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not just is food irradiation
safe, but how should

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it be conducted?

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How should it not be conducted
and what would the effects

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really be?

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00:01:06,570 --> 00:01:09,000
And with stuff that we did
the last few classes, actually

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looking up research papers and
discerning which sources are

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real and which ones
are, let's just say,

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00:01:14,890 --> 00:01:18,480
not, for lack of a bunch
of four letter words,

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00:01:18,480 --> 00:01:22,230
you can tell for yourselves
what sources are actually

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worth looking at.

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00:01:23,490 --> 00:01:26,760
So just quickly go over the
basics of food irradiation

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and maybe five minutes before
we hit the primary sources.

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So the general idea
here for anyone

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that got into the reading,
which I'll pull up right here,

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is that we irradiate
food to do a whole bunch

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00:01:38,160 --> 00:01:39,113
of different things.

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00:01:39,113 --> 00:01:41,280
Can anyone tell me, what
are some of the reasons one

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00:01:41,280 --> 00:01:44,975
might irradiate food?

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00:01:44,975 --> 00:01:47,600
AUDIENCE: Bacteria like E. coli

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MICHAEL SHORT: Yeah,
gets rid of bacteria,

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00:01:49,350 --> 00:01:50,520
other harmful organisms.

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00:01:50,520 --> 00:01:52,860
It just kills other organisms.

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Like what?

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00:01:54,090 --> 00:01:56,920
Like bacteria.

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00:01:56,920 --> 00:01:57,840
Anyone else?

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00:01:57,840 --> 00:01:58,520
AUDIENCE: Bugs.

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00:01:58,520 --> 00:01:59,870
MICHAEL SHORT: Yes, insects.

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00:01:59,870 --> 00:02:03,260
It's actually used to either
kill or sterilize insects

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so that they don't
breathe and let's say--

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oh yeah, totally,
because the dose required

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to sterilize
something is usually

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a lot lower than the dose
required to kill something.

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Why do you guys think that is?

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00:02:16,050 --> 00:02:16,550
Yeah?

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AUDIENCE: To sterilize
[INAUDIBLE] all you have to do

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is kill off your
reproductive cells.

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MICHAEL SHORT: That's right.

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And anyone remember what
those quality factors

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look like for those
reproductive cells?

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AUDIENCE: Much higher.

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MICHAEL SHORT: That's right.

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Let me bring it up.

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Let me go into the dose
dosimetry and background.

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I think it'll help to
actually see the numbers here.

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Let's go to the tissue
quality factors.

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There we go.

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Right at the top of the
list, reproductive organs.

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So it takes a whole lot less
dose to sterilize something

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like insects or other
bacteria or things,

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or I don't know if you
can say sterilize viruses.

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It's still kind of under
debate whether viruses

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are technically alive.

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They're right on that
edge of what people

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would consider alive or not.

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And there's still
a debate going on

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about what does
alive really mean.

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Yeah.

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You can sterilize the
insect population.

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For example, who here's
bought a bag of rice before,

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and who here has found
some little rice bugs

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in that bag of rice before?

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Are you serious?

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I must shop at cheap store,
I find them all the time.

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But the nice thing is if
you irradiate them then

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they won't breed and continue
to eat and breed in the bag

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00:03:23,890 --> 00:03:25,390
and then you open
the bag and you've

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got a swarm of, I don't
know what those things are,

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rice weevils or something.

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I think I remember looking them
up once because I was like what

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00:03:31,915 --> 00:03:34,330
is this thing in the rice?

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00:03:34,330 --> 00:03:35,350
Yeah, it's gross.

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00:03:35,350 --> 00:03:36,980
But that's why we
do food irradiation.

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Now, what else?

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00:03:38,650 --> 00:03:40,400
What other reasons
might want to irradiate

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00:03:40,400 --> 00:03:42,770
food other than to kill
or sterilize things in it?

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00:03:46,210 --> 00:03:46,710
Yeah?

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AUDIENCE: Doesn't it
preserve like shelf lifes?

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00:03:49,260 --> 00:03:51,510
MICHAEL SHORT: It does
preserve shelf life, especially

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of things like fresh fruits,
vegetables, seeds, legumes.

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Anyone have any idea why?

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Yeah?

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AUDIENCE: Well, it seemed like
that would be just because it

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00:04:03,880 --> 00:04:05,932
kills things that eat it.

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MICHAEL SHORT: Yep.

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One would be it kills
things that eat it,

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but the other thing
is those plants have

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reproductive cells as well.

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00:04:15,490 --> 00:04:17,750
Let's pick a good example.

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00:04:17,750 --> 00:04:23,070
Anyone ever had really well
sprouted bean sprouts before?

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Like not the fresh ones,
but the really old ones?

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00:04:26,830 --> 00:04:29,900
Not old like they've sat
behind the fridge or something.

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OK.

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AUDIENCE: Like super sprouted?

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MICHAEL SHORT: Yeah,
super crazy sprouted.

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AUDIENCE: The super
crazy sprouted.

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MICHAEL SHORT: Anyone
remember what they taste like?

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They are kind of bitter
and rather unpleasant.

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So one of the main reasons
for irradiating food

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00:04:44,350 --> 00:04:46,770
is to prevent sprouting
and prevent germination

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because as soon as the plant
sprouts and starts to say like,

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00:04:49,270 --> 00:04:52,750
all right, let's grow, starts
to consume its store of sugars,

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water, nutrients
and everything else

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00:04:54,820 --> 00:04:56,920
and start generating
other flavors, which

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tend to be fairly off flavors.

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So another way that you can
keep things tasting good,

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00:05:03,490 --> 00:05:06,850
even if they don't have bugs or
weevils or insects or viruses

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00:05:06,850 --> 00:05:08,680
in them, is prevent
them from changing

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at all through their
normal metabolic processes.

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So it kind of freezes
the food in place.

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Well, since I
mentioned freezing,

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00:05:16,530 --> 00:05:18,490
there's another
little caveat to that.

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At what temperature do you
think would be the best

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00:05:20,800 --> 00:05:23,340
temperature to irradiate food?

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AUDIENCE: Cold temperatures.

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MICHAEL SHORT: You say
cold, and why do you say so?

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AUDIENCE: When you did that one
thing, the temperature'd grow.

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MICHAEL SHORT: Yeah,
let's bring it up.

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We talked about G-values
and temperature,

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00:05:36,000 --> 00:05:39,140
and I think it's a
little further in.

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It's in the chemical effects.

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00:05:41,440 --> 00:05:47,520
So I'll jog your guy's memory
a bit from just a week ago

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00:05:47,520 --> 00:05:49,410
where we were talking
about G-values

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00:05:49,410 --> 00:05:53,180
or the number of different
radiolytic byproducts

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00:05:53,180 --> 00:05:54,990
of radiolysis byproducts
that are formed

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00:05:54,990 --> 00:05:56,350
as a function of temperature.

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00:05:56,350 --> 00:05:58,350
I'm not going to full
screen that because that's

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00:05:58,350 --> 00:05:59,532
going to get all freaky.

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But you can see that there's
a whole lot more of them

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00:06:01,740 --> 00:06:03,780
formed as a function
of temperature.

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What's not shown here
is what happens when

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this reaches 0 degrees Celsius?

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What happens to water
at 0 degrees Celsius?

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00:06:18,100 --> 00:06:19,900
Just look outside,
what do we got?

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It freezes, OK.

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All these G-values
are calculated

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assuming the free species are
diffusing in liquid water.

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When you freeze the
food, you pretty much

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shut down diffusion.

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When you shut down diffusion,
do these chemicals react or not

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in a different way?

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Can they move to
find each other?

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No, they're frozen in place.

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You're stuck at the
diffusion coefficient

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in ice, which is
a whole lot slower

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than in free flowing water.

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So in this way, you can kill
whatever organisms are there

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even if they can survive
freezing by directly damaging

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their DNA, without altering
as many of the foods

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normal tastes, flavors,
colors, whatever.

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And speaking of
taste flavors colors,

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I want to bring up some
of the pseudoscience.

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It didn't take long to
find a couple of things

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on the internet
talking about how we

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00:07:13,690 --> 00:07:15,910
shouldn't eat irradiated food.

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And to that I say,
well next time

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00:07:17,740 --> 00:07:19,960
you spend five weeks
straight on the toilet

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00:07:19,960 --> 00:07:22,840
you may be thankful
for food irradiation.

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So let's look to see
what sort of things

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could or couldn't happen
with food irradiation

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00:07:27,430 --> 00:07:30,280
based on random
internet article.

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00:07:30,280 --> 00:07:34,270
Again, not a useful source,
but let's see what they say.

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Damages food by breaking
up molecules and creating

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free radicals.

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00:07:38,210 --> 00:07:39,147
That's true.

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What's the question we should
be asking though is not

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00:07:41,355 --> 00:07:42,723
does it damage molecules?

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00:07:42,723 --> 00:07:43,640
But what do you think?

192
00:07:46,870 --> 00:07:47,535
Yeah?

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00:07:47,535 --> 00:07:49,987
AUDIENCE: Do the damaged
molecules have any effect?

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00:07:49,987 --> 00:07:50,820
MICHAEL SHORT: Yeah.

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00:07:50,820 --> 00:07:53,610
So one, do the damaged
molecules have any effect?

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00:07:53,610 --> 00:07:55,990
Were those same damaged
molecules there to begin with?

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00:07:55,990 --> 00:07:58,800
And the other question I
want to ask is how much?

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00:07:58,800 --> 00:08:01,112
How much is always
the question you

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00:08:01,112 --> 00:08:02,820
want to come back with
when somebody says

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00:08:02,820 --> 00:08:06,390
isn't it true that radiation
does binary effect?

201
00:08:06,390 --> 00:08:10,586
Causes cancer, kills
babies, whatever you want?

202
00:08:10,586 --> 00:08:11,430
Sure, enough.

203
00:08:11,430 --> 00:08:13,830
But the question is how much?

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00:08:13,830 --> 00:08:17,070
So there's a second
source top 10 reasons

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00:08:17,070 --> 00:08:19,293
for opposing food irradiation.

206
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Let's go through these
a little bit one by one

207
00:08:21,210 --> 00:08:23,418
and look at some of the
references, which they're not

208
00:08:23,418 --> 00:08:24,840
all bad.

209
00:08:24,840 --> 00:08:25,590
So let's see.

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00:08:25,590 --> 00:08:28,020
In legalizing food
irradiation we

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00:08:28,020 --> 00:08:31,500
did not determine a level which
food can be exposed and still

212
00:08:31,500 --> 00:08:32,909
be safe for human consumption.

213
00:08:32,909 --> 00:08:35,490
So let's think about
what that actually means.

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00:08:35,490 --> 00:08:38,850
We never hit that LD
50 or LD 10 or whatever

215
00:08:38,850 --> 00:08:43,350
dose we found that will
cause ill effects in humans.

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00:08:43,350 --> 00:08:45,880
I would argue this
is a good thing.

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00:08:45,880 --> 00:08:48,550
If we haven't had any documented
cases of people getting

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00:08:48,550 --> 00:08:52,000
sick from food
irradiation and we already

219
00:08:52,000 --> 00:08:54,910
get the effects that we want
like stopping germination,

220
00:08:54,910 --> 00:08:57,250
sprouting, killing bad
things, then great,

221
00:08:57,250 --> 00:08:58,660
let's not go higher.

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00:08:58,660 --> 00:08:59,890
Mission accomplished.

223
00:08:59,890 --> 00:09:02,800
Let's look at the
references again.

224
00:09:02,800 --> 00:09:05,470
Reference one, they
actually give a US code

225
00:09:05,470 --> 00:09:06,580
of federal regulations.

226
00:09:06,580 --> 00:09:09,890
Reference two, I
dare you to find

227
00:09:09,890 --> 00:09:12,560
what they were talking about.

228
00:09:12,560 --> 00:09:15,230
Various filings over
a period of 17 years.

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00:09:15,230 --> 00:09:19,460
AUDIENCE: Isn't that dating
publication Federal Register?

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00:09:19,460 --> 00:09:20,900
MICHAEL SHORT: I'm not sure.

231
00:09:20,900 --> 00:09:23,180
I think it might be
something more legit,

232
00:09:23,180 --> 00:09:25,430
but there may also be a
publication called the Federal

233
00:09:25,430 --> 00:09:26,330
Register.

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00:09:26,330 --> 00:09:28,310
I doubt the Federal
Register publication has

235
00:09:28,310 --> 00:09:30,977
what's called filings, but these
would be more official filings.

236
00:09:30,977 --> 00:09:34,022
But yeah, they're somewhere
in the archives of somewhere.

237
00:09:34,022 --> 00:09:34,730
But at any rate--

238
00:09:34,730 --> 00:09:37,905
AUDIENCE: [INAUDIBLE]
from class.

239
00:09:37,905 --> 00:09:40,280
MICHAEL SHORT: Again, I would
argue that this is actually

240
00:09:40,280 --> 00:09:40,830
a good thing.

241
00:09:40,830 --> 00:09:45,015
We don't know to what level food
irradiation can harm people.

242
00:09:45,015 --> 00:09:46,640
Now, let's think
about some of the ways

243
00:09:46,640 --> 00:09:49,502
in which if done incorrectly
it could harm people.

244
00:09:49,502 --> 00:09:51,460
Without me telling you
ahead of time-- and this

245
00:09:51,460 --> 00:09:53,390
we'll see who did a
little bit of the reading.

246
00:09:53,390 --> 00:09:54,950
--what sort of
types of radiation

247
00:09:54,950 --> 00:09:57,920
do we use to irradiate
food, and why?

248
00:09:57,920 --> 00:10:04,880
We have our choice of alphas,
betas, positrons, gammas,

249
00:10:04,880 --> 00:10:08,630
neutrons, heavy ions, et cetera.

250
00:10:11,330 --> 00:10:12,620
What would you use, and why?

251
00:10:12,620 --> 00:10:13,120
Yeah?

252
00:10:13,120 --> 00:10:14,620
AUDIENCE: Presumably
ionizing so you

253
00:10:14,620 --> 00:10:18,212
don't have to activate any
of the things [INAUDIBLE]..

254
00:10:18,212 --> 00:10:20,260
MICHAEL SHORT: So you
said presumably ionizing.

255
00:10:20,260 --> 00:10:21,596
AUDIENCE: Yeah, so you
don't activate them

256
00:10:21,596 --> 00:10:22,940
and you get
radioactive thiamine.

257
00:10:22,940 --> 00:10:23,590
MICHAEL SHORT: OK.

258
00:10:23,590 --> 00:10:25,548
Which of these types of
radiation are ionizing?

259
00:10:25,548 --> 00:10:28,902
AUDIENCE: Sulphur,
[INAUDIBLE],, gamma.

260
00:10:28,902 --> 00:10:30,735
MICHAEL SHORT: What do
you mean by ionizing?

261
00:10:30,735 --> 00:10:33,370
AUDIENCE: So they can lead to
ionizations in the material.

262
00:10:33,370 --> 00:10:34,180
MICHAEL SHORT: Oh.

263
00:10:34,180 --> 00:10:36,513
I would argue that every one
of these types of radiation

264
00:10:36,513 --> 00:10:37,228
can ionize.

265
00:10:37,228 --> 00:10:38,770
As we've seen, they
can all knock out

266
00:10:38,770 --> 00:10:40,270
electrons or other nuclei.

267
00:10:40,270 --> 00:10:42,580
But you're getting at
an important point.

268
00:10:42,580 --> 00:10:44,110
Can anyone help Alex clarify?

269
00:10:44,110 --> 00:10:46,460
because you're getting
onto the right track.

270
00:10:46,460 --> 00:10:47,646
Anyone?

271
00:10:47,646 --> 00:10:48,146
Yeah?

272
00:10:48,146 --> 00:10:49,592
AUDIENCE: [INAUDIBLE].

273
00:10:55,730 --> 00:10:56,480
MICHAEL SHORT: OK.

274
00:10:56,480 --> 00:10:58,370
So you may not want to
use heavy ions or alphas

275
00:10:58,370 --> 00:11:00,720
because you don't want to
plant anything in the material.

276
00:11:00,720 --> 00:11:02,387
Are you worried about
implanting helium?

277
00:11:05,500 --> 00:11:06,187
What about iron?

278
00:11:06,187 --> 00:11:08,020
I mean let's say you
want to use carbon ions

279
00:11:08,020 --> 00:11:10,800
and the food is Carboniferous.

280
00:11:10,800 --> 00:11:11,880
That's OK.

281
00:11:11,880 --> 00:11:14,533
But what about some of
these types of radiation

282
00:11:14,533 --> 00:11:16,200
are quite different
from the others when

283
00:11:16,200 --> 00:11:19,200
we were talking about
everything from gamma

284
00:11:19,200 --> 00:11:21,510
to charged particle to
neutron interactions?

285
00:11:21,510 --> 00:11:23,160
What sort of things
might we look

286
00:11:23,160 --> 00:11:25,920
at as criteria to
determine whether or not

287
00:11:25,920 --> 00:11:30,360
we want to use this
for food irradiation?

288
00:11:30,360 --> 00:11:31,800
Stopping power.

289
00:11:31,800 --> 00:11:36,450
So stopping power, which is
related directly to range.

290
00:11:36,450 --> 00:11:39,540
So let's pick an
energy of around 1 MeV.

291
00:11:42,270 --> 00:11:44,880
How do you find the range
of 1 MeV alphas in food?

292
00:11:47,420 --> 00:11:47,920
Great.

293
00:11:47,920 --> 00:11:49,660
That's what I was
going to say too.

294
00:11:49,660 --> 00:11:51,160
You can either do
the calculations,

295
00:11:51,160 --> 00:11:53,320
or like most of us
actually do, we just

296
00:11:53,320 --> 00:11:55,000
run a quick simulation
that integrates

297
00:11:55,000 --> 00:11:56,000
all those calculations.

298
00:11:56,000 --> 00:11:57,880
So let's do that right now.

299
00:11:57,880 --> 00:12:04,540
So we will take one MeV
helium or 1,000k EV helium.

300
00:12:04,540 --> 00:12:09,170
We will approximate
food as water

301
00:12:09,170 --> 00:12:12,860
with a stoichiometry
of 2 to 1, a density

302
00:12:12,860 --> 00:12:18,820
of 1 gram per cubic centimeter,
and let's allow for--

303
00:12:18,820 --> 00:12:22,170
I think I already know what
the answer is going to be.

304
00:12:22,170 --> 00:12:23,105
--10 microns.

305
00:12:26,540 --> 00:12:27,950
What are we getting for a range?

306
00:12:27,950 --> 00:12:32,870
5, 6 microns for alpha
particles in water.

307
00:12:32,870 --> 00:12:36,320
How well would alpha
particles sterilize food?

308
00:12:36,320 --> 00:12:37,060
Not.

309
00:12:37,060 --> 00:12:44,320
So let's say you have
a chicken with diameter

310
00:12:44,320 --> 00:12:50,210
around 40 centimeters.

311
00:12:50,210 --> 00:12:52,400
The alpha particles would
penetrate the chicken

312
00:12:52,400 --> 00:12:55,280
to a depth of
approximately 6 microns.

313
00:12:55,280 --> 00:12:58,310
So alpha particles
are probably out.

314
00:12:58,310 --> 00:13:01,430
What else is out
based on range alone?

315
00:13:01,430 --> 00:13:03,530
Heavy ions.

316
00:13:03,530 --> 00:13:08,220
How far do you think ion ions
would penetrate into a chicken?

317
00:13:08,220 --> 00:13:09,030
Not far at all.

318
00:13:09,030 --> 00:13:10,880
Let's find out.

319
00:13:10,880 --> 00:13:15,110
Iron ions, I'm going to
shrink the scale to 1 micron.

320
00:13:18,272 --> 00:13:20,605
We actually kind of did this
on the homework, didn't we?

321
00:13:20,605 --> 00:13:24,872
I had you guys look at the range
of lighter and heavier ions.

322
00:13:24,872 --> 00:13:26,330
What I'm hoping is
that you'll have

323
00:13:26,330 --> 00:13:28,460
some sort of an intuition
for how far ions

324
00:13:28,460 --> 00:13:29,430
tend to go in material.

325
00:13:29,430 --> 00:13:34,310
So as you go heavier, does
the range go up or down?

326
00:13:34,310 --> 00:13:36,050
Range goes down.

327
00:13:36,050 --> 00:13:39,560
As we expect we're getting
just about 2 microns of chicken

328
00:13:39,560 --> 00:13:41,930
with heavy iron ions.

329
00:13:41,930 --> 00:13:45,130
So what could you do to get
those to penetrate farther?

330
00:13:49,330 --> 00:13:51,190
Yeah, so you could
boost the energy.

331
00:13:51,190 --> 00:13:53,500
So if you were to boost
the energy of the alphas--

332
00:13:53,500 --> 00:13:54,000
let's see.

333
00:13:54,000 --> 00:13:57,960
First of all, with our
typical range relation

334
00:13:57,960 --> 00:14:02,040
where a range is roughly
proportional to kinetic energy

335
00:14:02,040 --> 00:14:05,878
squared, how much
more energy would we

336
00:14:05,878 --> 00:14:07,920
have to impart to the
alphas in order to get them

337
00:14:07,920 --> 00:14:09,600
to the center of the chicken?

338
00:14:12,580 --> 00:14:14,100
Well let's try and work it out.

339
00:14:16,950 --> 00:14:22,140
The range was about 6 microns
and an energy of 1 MeV

340
00:14:22,140 --> 00:14:25,690
and we want to get to
about 20 centimeters.

341
00:14:25,690 --> 00:14:27,900
Let's call that 6 centimeters.

342
00:14:27,900 --> 00:14:32,920
We're just going to use
this approximation for now.

343
00:14:32,920 --> 00:14:36,630
And if we want to go from
6 microns to 6 centimeters,

344
00:14:36,630 --> 00:14:41,983
that is four orders
of magnitude.

345
00:14:41,983 --> 00:14:43,650
So how many orders
of magnitude would we

346
00:14:43,650 --> 00:14:47,260
need to increase the energy
of the alphas to get through?

347
00:14:47,260 --> 00:14:47,760
OK.

348
00:14:47,760 --> 00:14:50,910
So we'd have to go to,
let's say, 100 MeV you said.

349
00:14:50,910 --> 00:14:52,780
Let's find out.

350
00:14:52,780 --> 00:14:55,750
We can just check this.

351
00:14:55,750 --> 00:14:59,170
So we'll switch back
to alphas at 100 MeV.

352
00:14:59,170 --> 00:15:02,830
This is already looking
to be fairly uneconomical.

353
00:15:02,830 --> 00:15:05,910
But this is physics,
so let's find out.

354
00:15:05,910 --> 00:15:08,130
OK.

355
00:15:08,130 --> 00:15:10,920
So we're at about
1.5 centimeters.

356
00:15:10,920 --> 00:15:13,870
And that's again
because at high energies

357
00:15:13,870 --> 00:15:18,030
this range relation changes
to about proportional

358
00:15:18,030 --> 00:15:20,778
to t for really high energies.

359
00:15:20,778 --> 00:15:22,320
So we know we're
going to have to get

360
00:15:22,320 --> 00:15:27,210
to around a GeV alphas in order
to food irradiate chicken.

361
00:15:27,210 --> 00:15:28,650
That sounds really expensive.

362
00:15:28,650 --> 00:15:29,310
Yeah.

363
00:15:29,310 --> 00:15:32,610
The proton cyclotron and
MGH is about 250 MeV,

364
00:15:32,610 --> 00:15:37,290
and we're talking an eight
or nine figure installation.

365
00:15:37,290 --> 00:15:39,270
Not worth it to irradiate food.

366
00:15:39,270 --> 00:15:43,540
What else might go wrong
with GeV alpha particles?

367
00:15:43,540 --> 00:15:45,930
What may you induce?

368
00:15:45,930 --> 00:15:46,430
Yeah?

369
00:15:46,430 --> 00:15:47,900
AUDIENCE: Bremsstrahlung
radiation.

370
00:15:47,900 --> 00:15:49,858
MICHAEL SHORT: Lot of
Bremsstrahlung radiation.

371
00:15:49,858 --> 00:15:52,790
We pretty much ignored
Bremsstrahlung of things

372
00:15:52,790 --> 00:15:54,570
like alpha particles
and protons.

373
00:15:54,570 --> 00:15:58,577
But once you get into the GeV
or tera electron volt range,

374
00:15:58,577 --> 00:16:00,410
you are going to get a
lot of Bremsstrahlung

375
00:16:00,410 --> 00:16:02,700
and shielding those x-rays
is going to be a mess.

376
00:16:02,700 --> 00:16:03,200
OK.

377
00:16:03,200 --> 00:16:07,513
So let's say we've
excluded alphas and ions

378
00:16:07,513 --> 00:16:08,930
for the purposes
of physics and we

379
00:16:08,930 --> 00:16:11,720
are left with batas,
positrons, gamma and neutrons.

380
00:16:14,205 --> 00:16:14,705
What next?

381
00:16:17,582 --> 00:16:19,720
AUDIENCE: Neutrons
are also expensive.

382
00:16:19,720 --> 00:16:21,610
MICHAEL SHORT:
Neutrons are expensive.

383
00:16:21,610 --> 00:16:25,090
You either need a reactor,
a spallation source,

384
00:16:25,090 --> 00:16:28,600
or a little pulsed fusion
device, two of which

385
00:16:28,600 --> 00:16:30,280
we have down the street.

386
00:16:30,280 --> 00:16:32,342
Let's say you had a
cheap source of neutrons.

387
00:16:32,342 --> 00:16:34,300
One of those, if you
build it and there's money

388
00:16:34,300 --> 00:16:36,032
to be made then they will-- no.

389
00:16:36,032 --> 00:16:37,990
If there's money to be
made they will build it,

390
00:16:37,990 --> 00:16:40,282
and if you build it, they
will come with their chickens

391
00:16:40,282 --> 00:16:41,500
for irradiation.

392
00:16:41,500 --> 00:16:44,890
Why else physically would
you not want to use neutrons

393
00:16:44,890 --> 00:16:46,210
to irradiate food?

394
00:16:46,210 --> 00:16:48,077
AUDIENCE: They
damage everything.

395
00:16:48,077 --> 00:16:49,660
MICHAEL SHORT: They
damage everything.

396
00:16:49,660 --> 00:16:51,280
That's OK, right?

397
00:16:51,280 --> 00:16:54,730
If they're damaging living
organisms more than the food

398
00:16:54,730 --> 00:16:56,470
itself, that's OK.

399
00:16:56,470 --> 00:16:59,650
But what do neutrons tend to do
when they interact with matter?

400
00:16:59,650 --> 00:17:02,620
And that's as specific as I
can make the question so far.

401
00:17:07,140 --> 00:17:09,579
The correct answer
is everything.

402
00:17:09,579 --> 00:17:10,079
Like what?

403
00:17:10,079 --> 00:17:10,815
Chris?

404
00:17:10,815 --> 00:17:13,603
AUDIENCE: Well, like Alex
said, they could activate--

405
00:17:13,603 --> 00:17:14,297
[AUDIO OUT]

406
00:17:14,297 --> 00:17:15,089
MICHAEL SHORT: Yes.

407
00:17:15,089 --> 00:17:17,422
So that's when I said you're
getting on the right track.

408
00:17:17,422 --> 00:17:20,010
So thanks you guys for
doing a team tag answer.

409
00:17:20,010 --> 00:17:22,935
Yes, they can activate things
at pretty much any energy.

410
00:17:26,180 --> 00:17:28,540
For this I'm going
to jump to Janis.

411
00:17:28,540 --> 00:17:30,200
Like I said, I like
to do things live,

412
00:17:30,200 --> 00:17:33,260
so show you guys that we
could do it on the fly

413
00:17:33,260 --> 00:17:37,950
and respond to your
comments in real time.

414
00:17:37,950 --> 00:17:39,080
It is showing, good.

415
00:17:39,080 --> 00:17:39,680
OK.

416
00:17:39,680 --> 00:17:41,240
Though this is a skill
I want to make sure

417
00:17:41,240 --> 00:17:42,740
that by the end of
this class, which

418
00:17:42,740 --> 00:17:45,020
is about 35 minutes
from now, you guys will

419
00:17:45,020 --> 00:17:47,248
know to jump to Janis
and start looking

420
00:17:47,248 --> 00:17:49,040
for the right cross-sections
because you're

421
00:17:49,040 --> 00:17:53,030
going to need it for the rest
of your life career time at MIT.

422
00:17:53,030 --> 00:17:55,760
Pick probably two
out of the three

423
00:17:55,760 --> 00:17:58,060
if you guys are going to
be nuclear somethings.

424
00:17:58,060 --> 00:18:00,380
I'm definitely in a
different database right now.

425
00:18:00,380 --> 00:18:03,260
I was in incident proton
data for other things

426
00:18:03,260 --> 00:18:05,240
that will become apparent soon.

427
00:18:05,240 --> 00:18:07,827
Let's go back to
incident neutron data.

428
00:18:07,827 --> 00:18:09,410
We'll use the same
database that we've

429
00:18:09,410 --> 00:18:13,010
been using all the time, the
ENDF most recent database.

430
00:18:13,010 --> 00:18:17,950
Look at the cross-sections
and let's assume

431
00:18:17,950 --> 00:18:20,110
you had some iron in your food.

432
00:18:20,110 --> 00:18:21,580
You are irradiating red meat.

433
00:18:25,160 --> 00:18:27,380
Nickel, copper, iron.

434
00:18:27,380 --> 00:18:30,815
Pretty common isotope of
iron could be iron 58.

435
00:18:33,510 --> 00:18:36,810
Let's now go down
and find the z gamma

436
00:18:36,810 --> 00:18:42,020
the neutron capture
cross-section for iron 58.

437
00:18:42,020 --> 00:18:45,830
It's decidedly non-zero at
all energies, which means

438
00:18:45,830 --> 00:18:47,540
you're going to make iron 59.

439
00:18:47,540 --> 00:18:51,038
What happens when
you make iron 59?

440
00:18:51,038 --> 00:18:52,580
I don't expect you
to know, but where

441
00:18:52,580 --> 00:18:53,705
do we go to get the answer?

442
00:18:56,300 --> 00:18:58,700
Wall, yep, Tyree,
that wall, the table

443
00:18:58,700 --> 00:19:02,520
of nuclides, whatever you
want, or the Brookhaven table,

444
00:19:02,520 --> 00:19:03,270
whatever you want.

445
00:19:03,270 --> 00:19:06,080
The point is the
table of nuclides.

446
00:19:06,080 --> 00:19:08,705
Let's take a look at iron
59 and see what it does.

447
00:19:11,900 --> 00:19:13,400
It is not stable.

448
00:19:13,400 --> 00:19:16,780
It has a half life of
greater than 10 days.

449
00:19:16,780 --> 00:19:19,340
It's a beta emitter
and it beta decays

450
00:19:19,340 --> 00:19:22,770
to cobalt 59, which
is a stable isotope.

451
00:19:22,770 --> 00:19:25,010
So you would be creating
an unjustable source

452
00:19:25,010 --> 00:19:26,690
of beta particles.

453
00:19:26,690 --> 00:19:28,530
Nasty stuff.

454
00:19:28,530 --> 00:19:31,140
Let's see what those
beta particles would do.

455
00:19:31,140 --> 00:19:34,240
They have about
a 1.5 MeV energy.

456
00:19:34,240 --> 00:19:37,700
Let's look at the decay diagram.

457
00:19:37,700 --> 00:19:40,310
There are a few transitions,
the most likely of which

458
00:19:40,310 --> 00:19:45,720
would give a beta and a gamma,
the most two likely of which

459
00:19:45,720 --> 00:19:47,760
would give a beta and a gamma.

460
00:19:47,760 --> 00:19:50,740
So you'd be ingesting a
dual beta gamma emitter.

461
00:19:50,740 --> 00:19:53,520
Now, to find out how far
would those betas go,

462
00:19:53,520 --> 00:19:57,080
as in are they energetic
enough to escape you or not,

463
00:19:57,080 --> 00:20:00,000
what do you use?

464
00:20:00,000 --> 00:20:01,290
AUDIENCE: [INAUDIBLE]

465
00:20:01,290 --> 00:20:04,020
MICHAEL SHORT:
[INAUDIBLE] electrons.

466
00:20:04,020 --> 00:20:05,300
AUDIENCE: Calculations.

467
00:20:05,300 --> 00:20:06,330
MICHAEL SHORT: Back
to calculations.

468
00:20:06,330 --> 00:20:08,872
Or I want to show you guys there
is a database for everything

469
00:20:08,872 --> 00:20:11,588
and it's always on NIST.

470
00:20:11,588 --> 00:20:14,130
I wonder if any of you guys have
found these for the homework

471
00:20:14,130 --> 00:20:15,922
because I didn't use
them in the solutions,

472
00:20:15,922 --> 00:20:19,410
but they're quite useful.

473
00:20:19,410 --> 00:20:21,540
NIST has a database
called ESTAR,

474
00:20:21,540 --> 00:20:24,780
stopping powers for electrons
where you can simply

475
00:20:24,780 --> 00:20:27,420
say graph the total
stopping power

476
00:20:27,420 --> 00:20:34,980
or range for electrons
in elements or materials.

477
00:20:34,980 --> 00:20:39,793
Materials, let's call
food as soft tissue.

478
00:20:39,793 --> 00:20:41,460
They don't have that,
let's go to water.

479
00:20:44,406 --> 00:20:47,980
And it gives you the range
of electrons in grams

480
00:20:47,980 --> 00:20:51,603
per square centimeter in water.

481
00:20:51,603 --> 00:20:53,020
What do we have
to do to make this

482
00:20:53,020 --> 00:20:55,390
into an actual range
in centimeters?

483
00:21:00,350 --> 00:21:01,840
AUDIENCE: You divide by density.

484
00:21:01,840 --> 00:21:03,990
MICHAEL SHORT:
Multiply by density.

485
00:21:03,990 --> 00:21:06,085
Yeah, I'm sorry,
divide in this case.

486
00:21:06,085 --> 00:21:08,830
So you have the range in
grams per square centimeter.

487
00:21:08,830 --> 00:21:10,690
If you divide by
density you're left

488
00:21:10,690 --> 00:21:12,550
with centimeters on the top.

489
00:21:12,550 --> 00:21:14,390
The density of liquid
water is about 1.

490
00:21:14,390 --> 00:21:17,380
So in the case of water, you
can simply read off this table

491
00:21:17,380 --> 00:21:20,950
if you're talking water at
25 C. So a beta particle

492
00:21:20,950 --> 00:21:24,390
with an energy of
about 1.5 MeV has

493
00:21:24,390 --> 00:21:29,100
a range of about a
centimeter in material.

494
00:21:29,100 --> 00:21:31,290
Not something you'd
want to ingest

495
00:21:31,290 --> 00:21:34,440
because around 1 centimeter away
from wherever the betas end up

496
00:21:34,440 --> 00:21:36,120
they would do a
whole lot of damage

497
00:21:36,120 --> 00:21:39,420
at the end of their range where
they have the highest stopping

498
00:21:39,420 --> 00:21:40,410
power.

499
00:21:40,410 --> 00:21:46,050
So we for many, many
reasons, least of which

500
00:21:46,050 --> 00:21:50,620
is activation, neutrons are out.

501
00:21:50,620 --> 00:21:52,830
So we do not irradiate
food with neutrons

502
00:21:52,830 --> 00:21:56,015
because they will
induce radiotoxicity.

503
00:21:56,015 --> 00:21:57,390
So for anyone that
tells you, oh,

504
00:21:57,390 --> 00:21:59,550
don't you stick food in a
reactor to irradiate it,

505
00:21:59,550 --> 00:22:01,530
the answer is definitely not.

506
00:22:01,530 --> 00:22:03,360
You don't want neutrons nearby.

507
00:22:03,360 --> 00:22:07,720
So we're left with different
types of betas and gammas.

508
00:22:07,720 --> 00:22:09,640
From our study
right here we just

509
00:22:09,640 --> 00:22:13,510
found out that betas
penetrate about 1 centimeter

510
00:22:13,510 --> 00:22:16,780
into materials at 1.5 MeV.

511
00:22:16,780 --> 00:22:18,992
So how energetic do we
have to get them to get

512
00:22:18,992 --> 00:22:20,200
to the center of the chicken?

513
00:22:23,720 --> 00:22:26,220
If range is proportional
to t squared

514
00:22:26,220 --> 00:22:33,920
and our range at 1 MeV or 1.5
MeV is about 1 centimeter--

515
00:22:33,920 --> 00:22:35,660
if we want to go
to 20 centimeters,

516
00:22:35,660 --> 00:22:37,130
about how much more
energetic do we

517
00:22:37,130 --> 00:22:39,590
have to get the betas to
irradiate the whole chicken?

518
00:22:45,013 --> 00:22:48,620
AUDIENCE: At least
10 times [INAUDIBLE]..

519
00:22:48,620 --> 00:22:49,120
Probably.

520
00:22:49,120 --> 00:22:50,703
MICHAEL SHORT: Let's
go with 10 times.

521
00:22:50,703 --> 00:22:55,150
Let's go to 15 MeV, and we
can just read off this chart.

522
00:22:55,150 --> 00:23:00,730
At 15 MeV we're
getting on about--

523
00:23:00,730 --> 00:23:02,830
now keep in mind, this
appears to be a double log

524
00:23:02,830 --> 00:23:06,290
scale, so that right there is
10, that right there is 100.

525
00:23:06,290 --> 00:23:08,990
Yeah, we're getting
towards 10 centimeters.

526
00:23:08,990 --> 00:23:11,150
If we want to see
where it is at 20,

527
00:23:11,150 --> 00:23:14,230
the log marker line
is kind of missing,

528
00:23:14,230 --> 00:23:15,400
but it comes to about here.

529
00:23:15,400 --> 00:23:21,760
If we go down, we're
getting around 30 or 40 MeV.

530
00:23:21,760 --> 00:23:25,830
How reasonable does that
sound for linear accelerator?

531
00:23:25,830 --> 00:23:26,850
Fairly.

532
00:23:26,850 --> 00:23:28,620
It's not unreasonable.

533
00:23:28,620 --> 00:23:31,030
It would still be big.

534
00:23:31,030 --> 00:23:33,520
Yeah, it may not be efficient,
so we may not use betas

535
00:23:33,520 --> 00:23:35,267
to irradiate entire chickens.

536
00:23:35,267 --> 00:23:37,600
What if you're irradiating
strawberries that are roughly

537
00:23:37,600 --> 00:23:40,560
about a centimeter in diameter?

538
00:23:40,560 --> 00:23:43,710
How does a 1 MeV linac sound?

539
00:23:43,710 --> 00:23:45,380
We've got some of those.

540
00:23:45,380 --> 00:23:45,900
Yeah.

541
00:23:45,900 --> 00:23:49,030
We've got a 2.5 MeV linac
just down the street

542
00:23:49,030 --> 00:23:50,850
in building N40.

543
00:23:50,850 --> 00:23:52,110
So that's totally OK.

544
00:23:52,110 --> 00:23:56,910
You could use betas in order
to irradiate thin enough foods,

545
00:23:56,910 --> 00:23:59,730
food for which you
can reach the center

546
00:23:59,730 --> 00:24:02,090
with the range of the betas.

547
00:24:02,090 --> 00:24:04,970
Do you induce any
significant radiotoxicity?

548
00:24:08,640 --> 00:24:11,108
How do you find out?

549
00:24:11,108 --> 00:24:12,920
AUDIENCE: Experiments.

550
00:24:12,920 --> 00:24:14,720
MICHAEL SHORT: You
could run an experiment.

551
00:24:14,720 --> 00:24:18,015
Or what database would you jump
to to try to figure this out?

552
00:24:18,015 --> 00:24:18,848
AUDIENCE: Janis.

553
00:24:18,848 --> 00:24:20,390
MICHAEL SHORT: I
would jump to Janis.

554
00:24:20,390 --> 00:24:21,520
So let's go back there.

555
00:24:25,480 --> 00:24:29,020
Let's see if they have the
incident electron data.

556
00:24:29,020 --> 00:24:34,630
Yes, incident electron
data, the EXFOR database.

557
00:24:34,630 --> 00:24:37,070
It's good for charged particles.

558
00:24:37,070 --> 00:24:38,367
Let's look at iron 56.

559
00:24:38,367 --> 00:24:39,950
Let's say you're
irradiating red meat.

560
00:24:44,261 --> 00:24:46,350
I think this is just
total cross-section,

561
00:24:46,350 --> 00:24:49,780
so that's not going
to tell us much.

562
00:24:49,780 --> 00:24:56,210
It's also not loading and had
an error, and another error.

563
00:24:56,210 --> 00:24:56,780
Interesting.

564
00:24:56,780 --> 00:24:59,190
All right.

565
00:24:59,190 --> 00:25:02,710
Let's see if we have any other
interesting isotopes that

566
00:25:02,710 --> 00:25:04,250
have any good reactions.

567
00:25:04,250 --> 00:25:06,920
Guess not.

568
00:25:06,920 --> 00:25:08,960
All right.

569
00:25:08,960 --> 00:25:10,760
Well at any rate,
it's awfully difficult

570
00:25:10,760 --> 00:25:13,077
to induce radiotoxicity
with betas.

571
00:25:13,077 --> 00:25:14,660
There's another one
I didn't get into,

572
00:25:14,660 --> 00:25:16,035
which would be
protons, somewhere

573
00:25:16,035 --> 00:25:20,828
between alphas and betas
in terms of range and such.

574
00:25:20,828 --> 00:25:22,370
Does anyone know,
perhaps anyone that

575
00:25:22,370 --> 00:25:26,210
works in the vault, what happens
when you give very high energy

576
00:25:26,210 --> 00:25:27,406
protons?

577
00:25:27,406 --> 00:25:30,003
AUDIENCE: A lot of
gammas and neutrons.

578
00:25:30,003 --> 00:25:30,920
MICHAEL SHORT: Indeed.

579
00:25:30,920 --> 00:25:32,360
A lot of gammas and neutrons.

580
00:25:32,360 --> 00:25:35,150
The gammas, maybe no problem
at the irradiation facility;

581
00:25:35,150 --> 00:25:37,970
the neutrons, big problem.

582
00:25:37,970 --> 00:25:38,930
So find it again.

583
00:25:38,930 --> 00:25:42,493
We head to Janis, look at
the incident proton data.

584
00:25:42,493 --> 00:25:43,910
I've already scoped
this out and I

585
00:25:43,910 --> 00:25:48,650
know it's on the EXFOR
database of cross-sections.

586
00:25:48,650 --> 00:25:54,530
Let's go right back
up to our iron 56.

587
00:25:54,530 --> 00:25:57,710
So assume we're
irradiating red meat.

588
00:25:57,710 --> 00:25:59,270
What sort of
reactions do we have?

589
00:25:59,270 --> 00:26:06,675
Proton, n, something
with a few points to it.

590
00:26:06,675 --> 00:26:10,460
A-ha, a non-zero cross-section.

591
00:26:10,460 --> 00:26:13,970
So typically in the
range of five to 10 MeV,

592
00:26:13,970 --> 00:26:16,760
high energy protons will
start to create neutrons

593
00:26:16,760 --> 00:26:20,010
where a proton will come
in, a neutron will come out.

594
00:26:20,010 --> 00:26:25,070
So you would absolutely not
want to use protons above,

595
00:26:25,070 --> 00:26:28,100
let's say a safe
limit, of around 3 MeV.

596
00:26:28,100 --> 00:26:29,600
Then the problem
is what's the range

597
00:26:29,600 --> 00:26:33,630
of 3 MeV protons and stuff?

598
00:26:33,630 --> 00:26:35,820
Anyone have a
intuition for that?

599
00:26:38,900 --> 00:26:39,870
Pretty small.

600
00:26:39,870 --> 00:26:42,140
If you don't know generally
the order of magnitude,

601
00:26:42,140 --> 00:26:45,170
we'll head back to here to TRIM.

602
00:26:45,170 --> 00:26:50,975
We'll use 3 MeV protons.

603
00:26:50,975 --> 00:26:54,110
It's looking about a
millimeter of material.

604
00:26:54,110 --> 00:26:55,700
We're getting about
200 microns in.

605
00:26:55,700 --> 00:26:59,480
Not useful enough to be
useful for any sort of food

606
00:26:59,480 --> 00:27:00,110
irradiation.

607
00:27:00,110 --> 00:27:04,880
So protons again are out
for reasons of both neutron

608
00:27:04,880 --> 00:27:07,417
activation and range.

609
00:27:07,417 --> 00:27:09,285
AUDIENCE: When
people [INAUDIBLE],,

610
00:27:09,285 --> 00:27:11,027
it's like I sit next
to it all the time.

611
00:27:11,027 --> 00:27:11,860
MICHAEL SHORT: Sure.

612
00:27:11,860 --> 00:27:15,135
But what energy are the
protons that you're making?

613
00:27:15,135 --> 00:27:17,218
AUDIENCE: Well, I mean we
did a lot of low energy,

614
00:27:17,218 --> 00:27:20,343
but went down to like 10 MeV.

615
00:27:20,343 --> 00:27:22,510
MICHAEL SHORT: I highly
doubt you were sitting there

616
00:27:22,510 --> 00:27:24,165
during 10 MeV.

617
00:27:24,165 --> 00:27:25,915
AUDIENCE: I think the
highest we've gotten

618
00:27:25,915 --> 00:27:27,047
was probably 2 or 3.

619
00:27:27,047 --> 00:27:27,880
MICHAEL SHORT: Yeah.

620
00:27:27,880 --> 00:27:32,990
So 2 to 3 MeV, those proton
cross-sections jumped to 0.

621
00:27:32,990 --> 00:27:35,890
In fact, let me show
you that for a better--

622
00:27:35,890 --> 00:27:41,020
kill the TRIM thing because
that'll fry the computer.

623
00:27:41,020 --> 00:27:42,610
Let's look at, I
don't know, carbon,

624
00:27:42,610 --> 00:27:46,640
where there's a whole lot
more data, natural carbon.

625
00:27:46,640 --> 00:27:51,710
There should be lots of
nice cross-sections here.

626
00:27:51,710 --> 00:27:53,775
So in goes proton--

627
00:27:58,150 --> 00:28:00,610
maybe not for natural.

628
00:28:00,610 --> 00:28:04,312
Carbon 12 has over 100
different reactions.

629
00:28:07,090 --> 00:28:09,100
Something, n.

630
00:28:13,500 --> 00:28:16,170
Well, there's a lot of
reactions to sort through.

631
00:28:16,170 --> 00:28:18,570
Well, I don't want to waste
your time with that now.

632
00:28:18,570 --> 00:28:20,320
But anyway, hopefully
the cross-sections I

633
00:28:20,320 --> 00:28:22,890
showed you show you
that around 5 MeV

634
00:28:22,890 --> 00:28:24,580
or so you do start
to make neutrons.

635
00:28:24,580 --> 00:28:26,640
So if you can get
up to 10 MeV, that's

636
00:28:26,640 --> 00:28:28,473
why the vaults got that
forefoot thick door.

637
00:28:28,473 --> 00:28:30,598
You don't want to be in
the room when that happens.

638
00:28:30,598 --> 00:28:32,640
AUDIENCE: When we do a
lot of protons in class

639
00:28:32,640 --> 00:28:33,558
is not shielded.

640
00:28:33,558 --> 00:28:34,350
MICHAEL SHORT: Yes.

641
00:28:34,350 --> 00:28:37,540
But the class accelerator
only goes up to about 2 MeV.

642
00:28:37,540 --> 00:28:38,040
Yeah.

643
00:28:38,040 --> 00:28:40,320
And that's perfectly safe to
be standing around there for.

644
00:28:40,320 --> 00:28:42,334
AUDIENCE: We have downstairs
we can't next week

645
00:28:42,334 --> 00:28:43,770
because interlock.

646
00:28:43,770 --> 00:28:44,650
MICHAEL SHORT: Yep.

647
00:28:44,650 --> 00:28:46,840
Because of interlock, but not
because of physics, right?

648
00:28:46,840 --> 00:28:47,790
AUDIENCE: I'm in both.

649
00:28:47,790 --> 00:28:49,600
MICHAEL SHORT: OK, fair enough.

650
00:28:49,600 --> 00:28:50,800
Cool.

651
00:28:50,800 --> 00:28:52,750
So now we're left with gammas.

652
00:28:52,750 --> 00:28:54,550
Gammas work pretty well.

653
00:28:54,550 --> 00:28:56,470
They have very,
very long ranges.

654
00:28:56,470 --> 00:28:58,050
Even the concept
of range of a gamma

655
00:28:58,050 --> 00:29:00,370
is kind of a funny thing
to say because they undergo

656
00:29:00,370 --> 00:29:02,260
exponential attenuation.

657
00:29:02,260 --> 00:29:04,760
So you want either a high
enough flux of gammas

658
00:29:04,760 --> 00:29:07,960
that their low attenuation
won't matter or you

659
00:29:07,960 --> 00:29:10,210
use a lower energy gamma ray.

660
00:29:10,210 --> 00:29:13,720
So cobalt 60 irradiators that
give off those 1 and 1/2 MeV

661
00:29:13,720 --> 00:29:17,800
gammas are quite commonly
used for this sort of thing

662
00:29:17,800 --> 00:29:19,690
because the 1 and 1/2
MeV gammas will get

663
00:29:19,690 --> 00:29:21,393
through just about everything.

664
00:29:21,393 --> 00:29:22,810
You just need a
whole lot of them.

665
00:29:22,810 --> 00:29:26,260
Has anyone here seen or heard
of the cobalt irradiator

666
00:29:26,260 --> 00:29:28,510
downstairs in the
basement building six?

667
00:29:28,510 --> 00:29:30,220
We got one of these
things actually.

668
00:29:30,220 --> 00:29:32,063
It's just a sealed
source of cobalt.

669
00:29:32,063 --> 00:29:33,730
And the way you start
irradiation is you

670
00:29:33,730 --> 00:29:37,000
simply open the door
and the irradiation

671
00:29:37,000 --> 00:29:40,510
stops being shielded enough.

672
00:29:40,510 --> 00:29:44,890
Now, what things could go wrong
with super high energy gammas?

673
00:29:47,704 --> 00:29:49,423
AUDIENCE: Ironizations.

674
00:29:49,423 --> 00:29:51,590
MICHAEL SHORT: Ironizations
is what you want, right?

675
00:29:51,590 --> 00:29:53,660
You want to ionize
the water and the DNA

676
00:29:53,660 --> 00:29:56,690
of the bacteria or
the germinating cells

677
00:29:56,690 --> 00:29:58,670
so that they get destroyed.

678
00:29:58,670 --> 00:30:03,084
What else could you induce
with super high energy gammas?

679
00:30:03,084 --> 00:30:05,480
AUDIENCE: [INAUDIBLE] electrons.

680
00:30:05,480 --> 00:30:07,815
MICHAEL SHORT: That's another
form of ionization, right?

681
00:30:07,815 --> 00:30:08,690
So that's a good one.

682
00:30:12,130 --> 00:30:16,200
Why don't I show
you a quick thing?

683
00:30:16,200 --> 00:30:18,780
Let's go to incident gamma data.

684
00:30:18,780 --> 00:30:23,100
I think the EXFOR database
will be pretty good.

685
00:30:23,100 --> 00:30:25,300
Let's go back up to iron again.

686
00:30:25,300 --> 00:30:27,370
We'll go with our
red meat example.

687
00:30:32,410 --> 00:30:36,030
Gamma, neutron.

688
00:30:36,030 --> 00:30:38,310
Anyone heard of gamma
induced neutron ejection?

689
00:30:41,250 --> 00:30:44,760
High enough energy
gamma rays will actually

690
00:30:44,760 --> 00:30:47,580
cause neutrons to be emitted.

691
00:30:47,580 --> 00:30:49,400
So gammas are a definite
yes from the point

692
00:30:49,400 --> 00:30:51,170
of view of physics.

693
00:30:51,170 --> 00:30:54,610
They're also going to
have to be less than about

694
00:30:54,610 --> 00:30:58,300
5 MeV because once you
get to around 5 MeV,

695
00:30:58,300 --> 00:31:00,820
or in the case of
iron 56 10 MeV,

696
00:31:00,820 --> 00:31:02,260
you end up with a non-zero.

697
00:31:02,260 --> 00:31:05,320
And actually fairly
significant like 0.1 barn

698
00:31:05,320 --> 00:31:08,920
cross-section for a gamma
goes in, a neutron comes out,

699
00:31:08,920 --> 00:31:11,260
and that neutron comes
out at whatever energy.

700
00:31:11,260 --> 00:31:13,000
It activates what's
nearby and makes

701
00:31:13,000 --> 00:31:16,930
all sorts of nasty isotopes
that decay the way they will.

702
00:31:16,930 --> 00:31:19,510
Do you guys remember too
from the neutrons discussion

703
00:31:19,510 --> 00:31:24,230
about photofission, the idea
that a gamma ray can induce

704
00:31:24,230 --> 00:31:26,480
fission of a heavy nucleus?

705
00:31:26,480 --> 00:31:28,940
So if there's any traces of
uranium in the food, which

706
00:31:28,940 --> 00:31:32,110
there always are, whatever,
what you don't want it to do

707
00:31:32,110 --> 00:31:34,660
is then make a whole
bunch of fission products

708
00:31:34,660 --> 00:31:37,720
because even a couple parts
per million of uranium which

709
00:31:37,720 --> 00:31:40,960
might be no big deal could
be a big deal if you turn it

710
00:31:40,960 --> 00:31:44,610
into fission products
instead of plain old uranium

711
00:31:44,610 --> 00:31:47,860
where it's just a heavy
metal, like lead, whatever.

712
00:31:47,860 --> 00:31:50,620
We can deal with a tiny
bit of lead in our food.

713
00:31:50,620 --> 00:31:52,150
Totally.

714
00:31:52,150 --> 00:31:54,700
Yeah, OK.

715
00:31:54,700 --> 00:31:58,570
So while looking through
these internet studies

716
00:31:58,570 --> 00:32:00,950
talking about--

717
00:32:00,950 --> 00:32:04,090
I don't like this kind
of argument number four,

718
00:32:04,090 --> 00:32:06,340
irradiation encourages
filthy conditions.

719
00:32:06,340 --> 00:32:08,340
I don't think that's a
fault of the irradiation.

720
00:32:08,340 --> 00:32:10,798
I think that's a fault of the
people who are like, oh cool,

721
00:32:10,798 --> 00:32:13,450
physics means that we
can relax our standards.

722
00:32:13,450 --> 00:32:15,180
These are separate arguments.

723
00:32:15,180 --> 00:32:19,200
And going through all these
things that, frankly either

724
00:32:19,200 --> 00:32:22,110
are false, are true,
but the question

725
00:32:22,110 --> 00:32:26,810
is how much, and are true
to such a small degree

726
00:32:26,810 --> 00:32:28,490
that it barely matters.

727
00:32:28,490 --> 00:32:33,640
And wading through a
lot of these things,

728
00:32:33,640 --> 00:32:37,270
let's say, PhD thesis,
articles in the ecologist,

729
00:32:37,270 --> 00:32:42,240
a lot of other FDA
papers, various filings,

730
00:32:42,240 --> 00:32:46,630
from the '60s came upon actually
a really useful document,

731
00:32:46,630 --> 00:32:50,230
this World Health Organization
study on the wholesomeness

732
00:32:50,230 --> 00:32:52,900
of food irradiated with
doses above 10 kilogray.

733
00:32:52,900 --> 00:32:53,560
It's modern.

734
00:32:53,560 --> 00:32:56,125
It was done by a peer
reviewed study group.

735
00:32:56,125 --> 00:32:58,000
It was commissioned for
a major organization,

736
00:32:58,000 --> 00:33:00,120
so I pulled it up.

737
00:33:00,120 --> 00:33:00,620
Yeah.

738
00:33:00,620 --> 00:33:04,750
It's like, OK, there's a
legit reference in here.

739
00:33:04,750 --> 00:33:06,490
I recommend you guys
look through this.

740
00:33:06,490 --> 00:33:08,620
It's quite fascinating
how many studies

741
00:33:08,620 --> 00:33:11,680
have been done on rather
higher irradiation doses.

742
00:33:11,680 --> 00:33:14,710
So you can usually get away
with stopping germination

743
00:33:14,710 --> 00:33:18,700
at around a kilogray or so,
rather low dose of radiation.

744
00:33:18,700 --> 00:33:21,730
The highest dose anyone would
use is about 50 kilogray.

745
00:33:21,730 --> 00:33:25,480
They specifically looked at the
highest order of magnitude dose

746
00:33:25,480 --> 00:33:28,510
that we use for food
irradiation and looked not just

747
00:33:28,510 --> 00:33:31,840
to say are there ill effects,
but what are the ill effects?

748
00:33:31,840 --> 00:33:33,880
What are the other
compounds that are made,

749
00:33:33,880 --> 00:33:35,460
and do they matter in the end?

750
00:33:35,460 --> 00:33:37,877
And I want to walk you guys
through a few of the bookmarks

751
00:33:37,877 --> 00:33:40,180
that I found pretty fascinating.

752
00:33:40,180 --> 00:33:43,990
I asked you guys about G-values
at low and high temperature.

753
00:33:43,990 --> 00:33:46,420
Here's a great plot
showing that right there.

754
00:33:46,420 --> 00:33:50,350
This is food irradiation done
at 20 and minus 40 Celsius

755
00:33:50,350 --> 00:33:53,880
to look at the amount
of ammonia, nitrates,

756
00:33:53,880 --> 00:33:55,930
ferrocyanides, things
that you might not

757
00:33:55,930 --> 00:33:58,570
want, and look at the difference
between irradiating at 20

758
00:33:58,570 --> 00:34:04,350
C and minus 40 C. Enormous.

759
00:34:04,350 --> 00:34:08,050
Why is that so, physically?

760
00:34:08,050 --> 00:34:09,582
AUDIENCE: Diffusion stops.

761
00:34:09,582 --> 00:34:10,540
MICHAEL SHORT: Exactly.

762
00:34:10,540 --> 00:34:13,449
Diffusion stops when you
cease to have a liquid.

763
00:34:13,449 --> 00:34:16,389
It doesn't stop completely,
but the diffusion constant

764
00:34:16,389 --> 00:34:18,100
of anything and a
solid it's going

765
00:34:18,100 --> 00:34:21,670
to be a whole lot slower than
that same anything in a liquid.

766
00:34:21,670 --> 00:34:24,040
And so this way you
can destroy the cells

767
00:34:24,040 --> 00:34:25,960
without all of the
radiolytic byproducts

768
00:34:25,960 --> 00:34:28,929
going around and damaging other
food molecules and other food

769
00:34:28,929 --> 00:34:30,960
cells.

770
00:34:30,960 --> 00:34:34,800
Then we got into the question
of off smells and funny sorts

771
00:34:34,800 --> 00:34:35,670
of changes.

772
00:34:35,670 --> 00:34:40,449
So one of the comments said
can change the flavor odor

773
00:34:40,449 --> 00:34:42,820
and texture of food,
pork can turn red,

774
00:34:42,820 --> 00:34:45,580
beef can smell like a wet dog,
vegetables could become mushy,

775
00:34:45,580 --> 00:34:48,010
et cetera, et cetera, et cetera.

776
00:34:48,010 --> 00:34:49,870
This review of studies
actually looked

777
00:34:49,870 --> 00:34:54,159
at what compounds are formed in
which foods, and by how much?

778
00:34:54,159 --> 00:34:56,590
The only thing they didn't
tell you is how do they smell?

779
00:34:56,590 --> 00:34:58,480
So I looked up a few of those.

780
00:34:58,480 --> 00:35:01,990
They looked at hexanes as
a function of fat content

781
00:35:01,990 --> 00:35:04,610
for a rather high
dose for 10 kilogray,

782
00:35:04,610 --> 00:35:08,620
or at least here everything is
in normalized per 10 kilogray.

783
00:35:08,620 --> 00:35:12,370
So this is the yield of this
compound in nanograms per gram.

784
00:35:12,370 --> 00:35:15,715
Does that sound like a big deal?

785
00:35:15,715 --> 00:35:17,090
It may not sound
like a big deal,

786
00:35:17,090 --> 00:35:19,670
but a lot of these
odiferous compounds

787
00:35:19,670 --> 00:35:23,040
are detectable by the human
nose in parts per billion.

788
00:35:23,040 --> 00:35:25,040
So they actually do matter.

789
00:35:25,040 --> 00:35:27,230
And I looked up to
see what sort of smell

790
00:35:27,230 --> 00:35:29,720
do hexanes typically have?

791
00:35:29,720 --> 00:35:35,960
The word was petrolic, smelling
like petrol or gasoline.

792
00:35:35,960 --> 00:35:38,060
Might not necessarily
be something you want.

793
00:35:38,060 --> 00:35:42,110
And it is true that fat
compounds when you break up

794
00:35:42,110 --> 00:35:45,560
these, let's say, fat
molecules, which usually contain

795
00:35:45,560 --> 00:35:48,080
three fatty acids,
those fatty acids

796
00:35:48,080 --> 00:35:50,635
themselves are very aromatic.

797
00:35:50,635 --> 00:35:52,010
You've heard that
expression fats

798
00:35:52,010 --> 00:35:54,100
where the flavor is, right?

799
00:35:54,100 --> 00:35:57,940
A lot of it is not just due to,
well, if you just eat butter,

800
00:35:57,940 --> 00:35:59,800
it's not that flavorful.

801
00:35:59,800 --> 00:36:01,906
Anyone ever tried?

802
00:36:01,906 --> 00:36:03,640
I'm glad I'm not the only one.

803
00:36:03,640 --> 00:36:05,410
OK, good.

804
00:36:05,410 --> 00:36:08,420
But where fat really comes
into play is when you heat it

805
00:36:08,420 --> 00:36:10,420
and it undergoes all sorts
of different chemical

806
00:36:10,420 --> 00:36:12,820
reactions with the
food nearby, liberating

807
00:36:12,820 --> 00:36:14,380
some of the fatty acids.

808
00:36:14,380 --> 00:36:17,890
It's part of why lamb smells
like lamb and nothing else,

809
00:36:17,890 --> 00:36:22,990
is fat's where the flavor is,
and 90% of flavor is smell.

810
00:36:22,990 --> 00:36:24,640
You've only got
five or six tastes

811
00:36:24,640 --> 00:36:26,320
I think that's still
under the debate,

812
00:36:26,320 --> 00:36:28,870
but you can smell thousands
of different compounds.

813
00:36:28,870 --> 00:36:30,142
And so they actually matter.

814
00:36:30,142 --> 00:36:32,100
So I started looking at
some of the other ones.

815
00:36:32,100 --> 00:36:38,510
Heptadecadiene in micrograms
per gram fat per 10

816
00:36:38,510 --> 00:36:43,390
gray for foods containing
a lot of linoleic acid.

817
00:36:43,390 --> 00:36:48,720
The smell, Carrion
beetle sex pheromones.

818
00:36:48,720 --> 00:36:51,070
The sex pheromones shouldn't
be what turns you off,

819
00:36:51,070 --> 00:36:52,458
it should be the Carrion beetle.

820
00:36:52,458 --> 00:36:53,125
What is Carrion?

821
00:36:55,920 --> 00:36:57,780
It's the beetles that
feed on rotting meat.

822
00:36:57,780 --> 00:37:01,140
So this is the juice that
rotting meat beetles secrete

823
00:37:01,140 --> 00:37:04,680
to attract other rotting
meat beetles nearby,

824
00:37:04,680 --> 00:37:06,330
to use polite language.

825
00:37:06,330 --> 00:37:09,190
It's probably something that
you don't want in your food,

826
00:37:09,190 --> 00:37:10,910
or is it?

827
00:37:10,910 --> 00:37:15,440
Does anybody know what
makes pork smell like pork?

828
00:37:15,440 --> 00:37:15,940
Is what?

829
00:37:15,940 --> 00:37:17,213
AUDIENCE: Do I want to know?

830
00:37:17,213 --> 00:37:18,880
MICHAEL SHORT: You're
going to find out.

831
00:37:22,900 --> 00:37:24,170
Who likes pork here?

832
00:37:24,170 --> 00:37:24,670
Awesome.

833
00:37:24,670 --> 00:37:26,530
I'm going to ruin your day.

834
00:37:26,530 --> 00:37:28,840
There's a compound
called skatole.

835
00:37:28,840 --> 00:37:31,660
Can anyone figure out
from the root of the word?

836
00:37:31,660 --> 00:37:33,550
Yeah.

837
00:37:33,550 --> 00:37:36,160
Anyone ever heard of that
wonderful barnyardy smell

838
00:37:36,160 --> 00:37:40,280
from a cut of free range pork?

839
00:37:40,280 --> 00:37:41,530
Anyone heard this term before?

840
00:37:41,530 --> 00:37:42,447
Just raise your hands.

841
00:37:42,447 --> 00:37:45,230
Anyone heard the nice
pork barnyardy smell?

842
00:37:45,230 --> 00:37:46,920
OK, a couple of people.

843
00:37:46,920 --> 00:37:49,530
That barnyardy smell is
parts per trillion or parts

844
00:37:49,530 --> 00:37:51,420
per billion of skatole.

845
00:37:51,420 --> 00:37:56,190
So tiniest littlest bit of poop.

846
00:37:56,190 --> 00:37:58,520
Yeah.

847
00:37:58,520 --> 00:38:00,110
The same sort of
compounds that you

848
00:38:00,110 --> 00:38:04,130
find in scat in
incredibly small amounts

849
00:38:04,130 --> 00:38:07,940
contribute to the wonderful
flavor of really good pork.

850
00:38:07,940 --> 00:38:09,620
So just because
these compounds are

851
00:38:09,620 --> 00:38:14,000
made in higher amounts with
higher amounts of fat or dose

852
00:38:14,000 --> 00:38:16,880
doesn't mean that they're
necessarily off flavors.

853
00:38:16,880 --> 00:38:19,250
But it is kind of
hilarious to see

854
00:38:19,250 --> 00:38:20,900
what other places
do you tend to find

855
00:38:20,900 --> 00:38:22,700
high concentrations of these?

856
00:38:22,700 --> 00:38:25,810
The next one down,
hexadecatriene

857
00:38:25,810 --> 00:38:28,100
from irradiation of muscle.

858
00:38:28,100 --> 00:38:30,770
The one paper I could find
that talked about this

859
00:38:30,770 --> 00:38:33,350
in a cocktail of
smell compounds comes

860
00:38:33,350 --> 00:38:38,180
from the odiferous
defensive stink glands

861
00:38:38,180 --> 00:38:40,820
of red something beetles.

862
00:38:40,820 --> 00:38:43,250
Yeah, sounds horrible, right?

863
00:38:43,250 --> 00:38:45,320
So if you stopped
there you might think,

864
00:38:45,320 --> 00:38:48,950
great, so radiation produces
odiferous defensive stink gland

865
00:38:48,950 --> 00:38:50,090
compounds.

866
00:38:50,090 --> 00:38:52,550
But as we know,
pork smells great.

867
00:38:52,550 --> 00:38:55,760
We don't necessarily know
in what concentrations--

868
00:38:55,760 --> 00:38:56,910
what is it?

869
00:38:56,910 --> 00:38:58,880
--hexadecatriene
would smell good

870
00:38:58,880 --> 00:39:00,250
or smell bad to the human nose.

871
00:39:00,250 --> 00:39:01,430
It's just no telling.

872
00:39:01,430 --> 00:39:03,890
There's some compounds in any
amount if you can detect them

873
00:39:03,890 --> 00:39:05,090
they're terrible.

874
00:39:05,090 --> 00:39:07,250
There's some compounds
that go from bad to good.

875
00:39:07,250 --> 00:39:10,080
There's some pounds that
go from good to bad.

876
00:39:10,080 --> 00:39:14,540
Anyone ever smell someone that's
slopped on perfume before?

877
00:39:14,540 --> 00:39:17,330
Would you describe
the smell as good?

878
00:39:17,330 --> 00:39:18,670
No.

879
00:39:18,670 --> 00:39:22,370
Perfume relies on lots of
different compounds in very,

880
00:39:22,370 --> 00:39:23,650
very small concentrations.

881
00:39:23,650 --> 00:39:25,930
It's supposed to be subtle
and enhance your own body

882
00:39:25,930 --> 00:39:26,800
chemistry.

883
00:39:26,800 --> 00:39:28,990
You're not supposed to
smell like a perfume factory

884
00:39:28,990 --> 00:39:30,310
explosion.

885
00:39:30,310 --> 00:39:32,500
So another sort of
real life analogy

886
00:39:32,500 --> 00:39:34,870
where too much of a
good smelling thing can

887
00:39:34,870 --> 00:39:36,770
smell really bad.

888
00:39:36,770 --> 00:39:37,700
Yeah.

889
00:39:37,700 --> 00:39:41,600
And so then going on from
the various odiferous

890
00:39:41,600 --> 00:39:44,547
compounds where a few other
points I wanted to-- oh no,

891
00:39:44,547 --> 00:39:45,380
there's another one.

892
00:39:45,380 --> 00:39:46,362
OK.

893
00:39:46,362 --> 00:39:48,320
Seems like the production
is pretty much linear

894
00:39:48,320 --> 00:39:51,620
with either dose or with the
abundance of the precursor

895
00:39:51,620 --> 00:39:53,030
normalized dose.

896
00:39:53,030 --> 00:39:55,160
This one you tend to
find in deodorants.

897
00:39:55,160 --> 00:39:57,720
What was the name
of this compound?

898
00:39:57,720 --> 00:39:59,653
Propanediol type.

899
00:39:59,653 --> 00:40:01,320
Don't know the structure
because I'm not

900
00:40:01,320 --> 00:40:04,350
an organic chemist, but things
you might find in deodorant.

901
00:40:04,350 --> 00:40:05,940
Again, no telling
whether or not this

902
00:40:05,940 --> 00:40:08,070
would be good or bad
in food and how much.

903
00:40:08,070 --> 00:40:10,840
That's always the question
I want you to remember.

904
00:40:10,840 --> 00:40:14,670
If somebody asks, isn't
binary effect bad?

905
00:40:14,670 --> 00:40:16,740
Isn't meta tag
binary effect bad?

906
00:40:16,740 --> 00:40:19,330
The question is
depends how much.

907
00:40:19,330 --> 00:40:19,830
Yeah?

908
00:40:19,830 --> 00:40:22,150
AUDIENCE: Do these like
graphs show how much more more

909
00:40:22,150 --> 00:40:24,795
there was afterwards or
just like how much there

910
00:40:24,795 --> 00:40:25,622
is in general?

911
00:40:25,622 --> 00:40:26,580
MICHAEL SHORT: They do.

912
00:40:26,580 --> 00:40:30,770
It shows the dose normalized
yield per 10 kilogray

913
00:40:30,770 --> 00:40:32,710
in micrograms per gram.

914
00:40:32,710 --> 00:40:34,890
So it shows that depending
on how much of whatever

915
00:40:34,890 --> 00:40:38,160
precursor, in this case
enzyme inactivated muscle

916
00:40:38,160 --> 00:40:41,160
there was, how much relative
amount of this compound

917
00:40:41,160 --> 00:40:42,042
existed.

918
00:40:42,042 --> 00:40:43,500
What these graphs
are telling us is

919
00:40:43,500 --> 00:40:45,540
they're pretty much
all linear and they're

920
00:40:45,540 --> 00:40:46,950
pretty much all the same for--

921
00:40:46,950 --> 00:40:48,830
I saw that as human for
a second, holy crap.

922
00:40:48,830 --> 00:40:50,550
My heart just skipped a beat.

923
00:40:50,550 --> 00:40:54,150
--ham beef, chicken, pork.

924
00:40:54,150 --> 00:40:56,370
Oh man.

925
00:40:56,370 --> 00:41:00,720
Anyway, going into
the conclusions, which

926
00:41:00,720 --> 00:41:03,330
again are strikingly different
than the internet article would

927
00:41:03,330 --> 00:41:07,470
have you believe, I wanted
to point things out.

928
00:41:07,470 --> 00:41:07,980
Interesting.

929
00:41:07,980 --> 00:41:12,060
Irradiating moist foods while
frozen in the absence of oxygen

930
00:41:12,060 --> 00:41:16,312
significantly decreases overall
chemical yields by about 80%

931
00:41:16,312 --> 00:41:18,270
So it's interesting you
can irradiate something

932
00:41:18,270 --> 00:41:22,050
to 50 kilogray at minus 30 C
and it does the same chemical

933
00:41:22,050 --> 00:41:25,200
change as 10 kilogray at
room or chilled temperatures,

934
00:41:25,200 --> 00:41:29,670
but you do that much more
damage to the organisms.

935
00:41:29,670 --> 00:41:34,920
So yeah, there you go, better to
irradiate at cold temperatures.

936
00:41:34,920 --> 00:41:39,750
And there's a few other
interesting conclusions.

937
00:41:39,750 --> 00:41:44,100
These radiolytic compounds, are
they found in food otherwise?

938
00:41:44,100 --> 00:41:45,990
Virtually all the
radiolytic products

939
00:41:45,990 --> 00:41:49,080
found in high dose irradiated
foods are either naturally

940
00:41:49,080 --> 00:41:53,070
present foods or produced in
thermally processed foods.

941
00:41:53,070 --> 00:41:56,190
Before food irradiation
you had heat sterilization.

942
00:41:56,190 --> 00:41:58,320
In fact we still
do for quite a bit.

943
00:41:58,320 --> 00:41:59,820
And folks, a lot
of times we'll talk

944
00:41:59,820 --> 00:42:03,540
about the amount of nutritional
decline, the amount of lack

945
00:42:03,540 --> 00:42:05,700
of nutrition from
irradiated foods,

946
00:42:05,700 --> 00:42:08,260
and they'll just say
it's a bad thing.

947
00:42:08,260 --> 00:42:10,450
That's not the right
fact to see here.

948
00:42:10,450 --> 00:42:15,450
Food preservation tends to
lower the nutritional content.

949
00:42:15,450 --> 00:42:20,150
And there's a few neat tables
I want you guys to look at.

950
00:42:20,150 --> 00:42:21,890
In terms of
macronutrients, do you

951
00:42:21,890 --> 00:42:25,280
lose the protein, the
fat, the carbohydrates

952
00:42:25,280 --> 00:42:27,420
from in this case,
gamma-irradiated mackerel,

953
00:42:27,420 --> 00:42:29,090
as a function of dose?

954
00:42:29,090 --> 00:42:30,500
Does anybody see a trend here?

955
00:42:34,470 --> 00:42:36,090
Take a sec to look
at the numbers.

956
00:42:40,495 --> 00:42:44,317
AUDIENCE: Seems like
it bumps in the middle.

957
00:42:44,317 --> 00:42:46,650
MICHAEL SHORT: It does seem
like the nutritional content

958
00:42:46,650 --> 00:42:50,070
goes a little bit up with
small doses, doesn't it?

959
00:42:50,070 --> 00:42:54,858
Would you necessarily believe
these data at first glance

960
00:42:54,858 --> 00:42:58,205
or at face value?

961
00:42:58,205 --> 00:42:59,580
What's missing
from this data set

962
00:42:59,580 --> 00:43:03,720
for you to draw a statistically
significant conclusion?

963
00:43:03,720 --> 00:43:05,040
AUDIENCE: Error bars.

964
00:43:05,040 --> 00:43:07,020
MICHAEL SHORT:
Error bars, right.

965
00:43:07,020 --> 00:43:09,030
If this is the
graph of, let's say,

966
00:43:09,030 --> 00:43:13,620
protein content versus dose
in gray and this is protein,

967
00:43:13,620 --> 00:43:16,740
the data appear to do
something like this.

968
00:43:16,740 --> 00:43:21,480
If the error bars
are like that then

969
00:43:21,480 --> 00:43:23,530
you can't draw any
meaningful conclusions.

970
00:43:23,530 --> 00:43:25,843
So one would have to
go back to the study

971
00:43:25,843 --> 00:43:27,510
to see hopefully they
actually had error

972
00:43:27,510 --> 00:43:29,130
bars in their measurements.

973
00:43:29,130 --> 00:43:31,020
So what I can
conclude from this is

974
00:43:31,020 --> 00:43:33,433
macronutrients
basically don't change

975
00:43:33,433 --> 00:43:35,100
with up to the highest
dose of radiation

976
00:43:35,100 --> 00:43:36,930
that we give to any food at all.

977
00:43:36,930 --> 00:43:38,970
What about the micronutrients?

978
00:43:38,970 --> 00:43:41,730
What about things like vitamins?

979
00:43:41,730 --> 00:43:46,060
They do go down somewhat,
and they're pretty linear.

980
00:43:46,060 --> 00:43:47,430
They're fairly linear with dose.

981
00:43:47,430 --> 00:43:49,720
It's not much to
be disputed there,

982
00:43:49,720 --> 00:43:53,160
is yes, irradiating
food does destroy

983
00:43:53,160 --> 00:43:56,310
some of the vitamins
and not the minerals.

984
00:43:56,310 --> 00:43:59,340
Why wouldn't gamma irradiation
destroy minerals in food?

985
00:44:02,170 --> 00:44:05,900
What's an example of a mineral
that you need for survival?

986
00:44:05,900 --> 00:44:06,770
AUDIENCE: Iron.

987
00:44:06,770 --> 00:44:07,603
MICHAEL SHORT: Iron.

988
00:44:07,603 --> 00:44:08,530
AUDIENCE: Calcium.

989
00:44:08,530 --> 00:44:11,180
MICHAEL SHORT: Calcium.

990
00:44:11,180 --> 00:44:14,520
Yeah, bunch of other elements
or inorganic compounds.

991
00:44:14,520 --> 00:44:17,310
Why does food irradiation
not affect mineral content?

992
00:44:25,118 --> 00:44:28,700
AUDIENCE: If you use low enough
energy gammas it's just not

993
00:44:28,700 --> 00:44:30,383
going to change paratonic.

994
00:44:30,383 --> 00:44:31,550
MICHAEL SHORT: That's right.

995
00:44:31,550 --> 00:44:31,670
Yeah.

996
00:44:31,670 --> 00:44:34,040
You stay below 5 MeV gammas
and there's literally

997
00:44:34,040 --> 00:44:37,850
no change in the elemental
composition of those minerals.

998
00:44:37,850 --> 00:44:40,040
The vitamins, however,
tend to be more complex

999
00:44:40,040 --> 00:44:42,830
organic compounds
that can be damaged.

1000
00:44:42,830 --> 00:44:45,290
And one of those big
ones is thiamine, better

1001
00:44:45,290 --> 00:44:46,810
known as vitamin B1.

1002
00:44:46,810 --> 00:44:49,350
So irradiated food is a
little bit less nutritious,

1003
00:44:49,350 --> 00:44:54,460
but they give a pretty
good explanation.

1004
00:44:54,460 --> 00:44:56,258
Let's see.

1005
00:44:56,258 --> 00:44:57,800
Think that's later
in the conclusion,

1006
00:44:57,800 --> 00:44:59,790
so we'll get to that.

1007
00:44:59,790 --> 00:45:01,170
Conclusions on nutrition.

1008
00:45:01,170 --> 00:45:01,920
Yeah, there we go.

1009
00:45:05,110 --> 00:45:07,830
So in this case, what
they're saying is, well yeah,

1010
00:45:07,830 --> 00:45:11,010
it takes away some thiamine,
but irradiated food

1011
00:45:11,010 --> 00:45:14,260
does not constitute the major
source of thiamine in the diet.

1012
00:45:14,260 --> 00:45:17,670
So even though it does
reduce the amount of thiamine

1013
00:45:17,670 --> 00:45:19,380
that you get, it
doesn't make a dent

1014
00:45:19,380 --> 00:45:21,490
in your overall
nutritional uptake

1015
00:45:21,490 --> 00:45:24,690
unless you eat nothing
but that irradiated food.

1016
00:45:24,690 --> 00:45:27,660
Does anyone remember when the
last case of scurvy in the US

1017
00:45:27,660 --> 00:45:29,140
happened?

1018
00:45:29,140 --> 00:45:31,680
Talking about single food diets.

1019
00:45:31,680 --> 00:45:34,090
Happened right here at MIT.

1020
00:45:34,090 --> 00:45:35,020
It was a while ago.

1021
00:45:35,020 --> 00:45:38,830
I think by now it would have
been over 10 or 15 years ago.

1022
00:45:38,830 --> 00:45:40,330
There was a student
that decided I'm

1023
00:45:40,330 --> 00:45:42,663
going to have the cheapest
food budget ever and live off

1024
00:45:42,663 --> 00:45:44,785
nothing but instant
packs of ramen.

1025
00:45:44,785 --> 00:45:46,660
Now, this is already a
nutritional nightmare,

1026
00:45:46,660 --> 00:45:47,785
but it got worse and worse.

1027
00:45:47,785 --> 00:45:50,500
So it was the ramen, the
flavor packs and water,

1028
00:45:50,500 --> 00:45:52,778
and that's just what this
person ate the whole time.

1029
00:45:52,778 --> 00:45:54,320
And then they decided,
you know what?

1030
00:45:54,320 --> 00:45:55,390
I don't really need
the flavor pack

1031
00:45:55,390 --> 00:45:57,432
because that's just a
bunch of sodium, taking out

1032
00:45:57,432 --> 00:46:00,370
whatever little
micronutrients were left.

1033
00:46:00,370 --> 00:46:03,880
And then the next logical step
was why bother cooking it?

1034
00:46:03,880 --> 00:46:07,420
And a few weeks later massive
constipation and scurvy ensued,

1035
00:46:07,420 --> 00:46:09,220
which is a disease
you don't see anymore,

1036
00:46:09,220 --> 00:46:11,025
from a deficiency
of vitamin C. So

1037
00:46:11,025 --> 00:46:13,150
if you're only eating one
food to begin with you've

1038
00:46:13,150 --> 00:46:17,300
got other problems have nothing
to do with food irradiation.

1039
00:46:17,300 --> 00:46:17,800
Yeah?

1040
00:46:17,800 --> 00:46:20,342
AUDIENCE: I'm not even surprised
that the last case of scurvy

1041
00:46:20,342 --> 00:46:21,810
was an MIT student.

1042
00:46:21,810 --> 00:46:24,870
MICHAEL SHORT: I'm not
surprised at all either.

1043
00:46:24,870 --> 00:46:26,688
I'm surprised Soylent
wasn't invented here.

1044
00:46:26,688 --> 00:46:28,730
It seems like the kind of
thing that someone here

1045
00:46:28,730 --> 00:46:29,397
would have done.

1046
00:46:32,220 --> 00:46:33,320
Anyway, let's take a look.

1047
00:46:33,320 --> 00:46:36,780
Ah, irradiation versus
heat sterilization.

1048
00:46:36,780 --> 00:46:39,420
From a nutritional
viewpoint, irradiated foods

1049
00:46:39,420 --> 00:46:43,680
are equivalent or superior to
thermally sterilized foods.

1050
00:46:43,680 --> 00:46:46,155
Why do you guys
think that might be?

1051
00:46:46,155 --> 00:46:47,780
AUDIENCE: They're
really sterilizing it

1052
00:46:47,780 --> 00:46:50,203
with denaturing most
of the proteins.

1053
00:46:50,203 --> 00:46:51,120
MICHAEL SHORT: Indeed.

1054
00:46:51,120 --> 00:46:53,190
So you'd actually get
some macronutrients

1055
00:46:53,190 --> 00:46:56,430
to disappear if you start to
denature or break down those,

1056
00:46:56,430 --> 00:46:58,410
and even for micronutrients.

1057
00:46:58,410 --> 00:47:02,790
The idea here is that the
amount of micronutrient content

1058
00:47:02,790 --> 00:47:05,610
will go down roughly
linearly with dose.

1059
00:47:05,610 --> 00:47:08,550
What happens when you reach the
temperature of destabilization

1060
00:47:08,550 --> 00:47:09,330
of those foods?

1061
00:47:09,330 --> 00:47:11,760
AUDIENCE: [INAUDIBLE]
dropped them.

1062
00:47:11,760 --> 00:47:13,620
MICHAEL SHORT: Yeah,
all of it goes away.

1063
00:47:13,620 --> 00:47:16,530
Once it's temperature
unstable, if you keep it

1064
00:47:16,530 --> 00:47:18,360
at that temperature
for long enough

1065
00:47:18,360 --> 00:47:20,680
you'll destroy pretty much
all the nutritional content.

1066
00:47:20,680 --> 00:47:24,240
So if the choice is between do
you heat or do you irradiate,

1067
00:47:24,240 --> 00:47:26,520
irradiating does less
damage in the end.

1068
00:47:31,310 --> 00:47:35,250
Anyone here ever had an
MRE, a Meal Ready to Eat?

1069
00:47:35,250 --> 00:47:38,128
How do they taste?

1070
00:47:38,128 --> 00:47:41,490
AUDIENCE: They're not great,
but they're not awful.

1071
00:47:41,490 --> 00:47:44,970
MICHAEL SHORT: But they
do last for like decades,

1072
00:47:44,970 --> 00:47:46,020
like many decades.

1073
00:47:46,020 --> 00:47:48,120
There's an entire
channel on YouTube

1074
00:47:48,120 --> 00:47:50,820
of this guy that just eats MREs
from further and further back.

1075
00:47:50,820 --> 00:47:54,480
I think he's made it as
far back as the Civil War

1076
00:47:54,480 --> 00:47:57,660
and ate actual moldy hard
tack from the Civil War.

1077
00:47:57,660 --> 00:48:00,120
But my point here is
that all the way back

1078
00:48:00,120 --> 00:48:03,480
to definitely to World War II
and perhaps beforehand, MREs

1079
00:48:03,480 --> 00:48:05,970
were sterilized with heat.

1080
00:48:05,970 --> 00:48:09,450
You put something in a metal and
plastic lined bag to keep out

1081
00:48:09,450 --> 00:48:10,842
all other organisms.

1082
00:48:10,842 --> 00:48:12,300
You heat it for
long enough to kill

1083
00:48:12,300 --> 00:48:16,260
every single other organism
and they last for decades.

1084
00:48:16,260 --> 00:48:19,530
And the question is, do you
want to eat what's in the bag?

1085
00:48:19,530 --> 00:48:22,230
If you want some fun
between studying for finals

1086
00:48:22,230 --> 00:48:25,020
listen to this guy's reaction
as he eats some of these 60

1087
00:48:25,020 --> 00:48:28,170
or 70-year-old MREs from World
War II of the Korean War.

1088
00:48:28,170 --> 00:48:30,600
AUDIENCE: Why would they
subject themselves to this?

1089
00:48:30,600 --> 00:48:32,830
MICHAEL SHORT: I don't
know, for attention.

1090
00:48:32,830 --> 00:48:35,590
AUDIENCE: [INAUDIBLE] gets stung
by a really painful insect,

1091
00:48:35,590 --> 00:48:36,567
and I will say why?

1092
00:48:36,567 --> 00:48:37,400
MICHAEL SHORT: Yeah.

1093
00:48:39,930 --> 00:48:42,950
At any rate, canned
food you can tell

1094
00:48:42,950 --> 00:48:45,003
has an awfully
different taste to it.

1095
00:48:45,003 --> 00:48:46,670
A lot of these cans
are heat sterilized.

1096
00:48:46,670 --> 00:48:48,495
They're pasteurized
and the heat themselves

1097
00:48:48,495 --> 00:48:50,120
generates a lot of
off flavors that you

1098
00:48:50,120 --> 00:48:53,480
can tell the difference between
fresh and canned green beans

1099
00:48:53,480 --> 00:48:56,540
in taste, texture, color,
mushiness, whatever other

1100
00:48:56,540 --> 00:48:58,580
qualifiers you give to food.

1101
00:48:58,580 --> 00:49:01,880
So to those opponents
of food irradiation,

1102
00:49:01,880 --> 00:49:03,740
I'd say consider
the alternatives,

1103
00:49:03,740 --> 00:49:06,110
either heat
sterilization or spending

1104
00:49:06,110 --> 00:49:08,662
most of your waking
hours in the bathroom.

1105
00:49:08,662 --> 00:49:12,920
AUDIENCE: How do you like
thermally sterilize meat

1106
00:49:12,920 --> 00:49:14,760
without cooking it?

1107
00:49:14,760 --> 00:49:16,760
I've always been really
confused about that.

1108
00:49:16,760 --> 00:49:20,390
MICHAEL SHORT: Yeah,
you can't necessarily.

1109
00:49:20,390 --> 00:49:22,460
There are also spores
of bacteria that

1110
00:49:22,460 --> 00:49:23,930
are incredibly heat tolerant.

1111
00:49:23,930 --> 00:49:26,358
So you can't necessarily
sterilize meat

1112
00:49:26,358 --> 00:49:27,150
without cooking it.

1113
00:49:27,150 --> 00:49:31,130
So the best thing to do is
to cook it, sealed in a can,

1114
00:49:31,130 --> 00:49:33,560
or sealed in something
and then don't unseal it

1115
00:49:33,560 --> 00:49:37,190
until consumption time.

1116
00:49:37,190 --> 00:49:37,740
Yeah.

1117
00:49:37,740 --> 00:49:40,710
There are other things that you
can sterilize without cooking

1118
00:49:40,710 --> 00:49:41,460
them, like milk.

1119
00:49:41,460 --> 00:49:42,702
Milk is pasteurized.

1120
00:49:42,702 --> 00:49:44,160
You heat it to a
temperature that's

1121
00:49:44,160 --> 00:49:47,220
sufficient to kill most
of the microorganisms

1122
00:49:47,220 --> 00:49:50,700
not to sterilize it, but
to increase its shelf life

1123
00:49:50,700 --> 00:49:55,530
so that it takes months instead
of hours for that microorganism

1124
00:49:55,530 --> 00:49:58,908
population to bloom
and ruin the milk.

1125
00:49:58,908 --> 00:50:01,200
I'm sure everyone here has
smelled spoiled milk before,

1126
00:50:01,200 --> 00:50:01,770
right?

1127
00:50:01,770 --> 00:50:03,312
Doesn't matter how
pasteurized it is.

1128
00:50:03,312 --> 00:50:06,270
Has anyone opened a carton of
expired milk after its shelf

1129
00:50:06,270 --> 00:50:07,090
life?

1130
00:50:07,090 --> 00:50:09,900
AUDIENCE: One time I
poured it into my cereal.

1131
00:50:09,900 --> 00:50:11,310
MICHAEL SHORT: Yeah.

1132
00:50:11,310 --> 00:50:13,920
That was a study in
two phase flow, right?

1133
00:50:13,920 --> 00:50:15,050
Liquid, solid.

1134
00:50:15,050 --> 00:50:17,010
Yeah.

1135
00:50:17,010 --> 00:50:18,360
Yep.

1136
00:50:18,360 --> 00:50:20,840
So there is some proof right
there, a few bacteria survive.

1137
00:50:20,840 --> 00:50:22,590
It's the same thing
with food irradiation,

1138
00:50:22,590 --> 00:50:24,630
you need an enormous
dose in order

1139
00:50:24,630 --> 00:50:26,590
to actually sterilize the food.

1140
00:50:26,590 --> 00:50:29,100
So this is usually the
only option for folks

1141
00:50:29,100 --> 00:50:32,050
with extremely compromised
immune systems in hospitals

1142
00:50:32,050 --> 00:50:34,800
is if you want to give
them actually sterile food

1143
00:50:34,800 --> 00:50:37,245
that's actually
palatable, you irradiate

1144
00:50:37,245 --> 00:50:39,260
it to like 50 kilogray.

1145
00:50:39,260 --> 00:50:42,780
And that kills just about
every single organism including

1146
00:50:42,780 --> 00:50:45,300
the long lived spores.

1147
00:50:45,300 --> 00:50:47,220
One other side benefit
of food irradiation

1148
00:50:47,220 --> 00:50:51,270
is the cells that survive have
been blasted by radiation.

1149
00:50:51,270 --> 00:50:55,260
They tend to be a lot weaker and
more sensitive to heat and pH

1150
00:50:55,260 --> 00:50:58,508
and temperature-- heat,
temperature, the same thing.

1151
00:50:58,508 --> 00:51:01,050
--so that the cells that make
it through the food irradiation

1152
00:51:01,050 --> 00:51:03,240
are more susceptible
to damage and then

1153
00:51:03,240 --> 00:51:06,126
it helps make things
a little bit safer.

1154
00:51:06,126 --> 00:51:09,540
I'm trying to see if there's
any other conclusions.

1155
00:51:09,540 --> 00:51:12,250
Oh yeah, the old who
cares about thiamine.

1156
00:51:12,250 --> 00:51:14,820
It's unlikely however, that the
irradiated foods of this type

1157
00:51:14,820 --> 00:51:17,220
would constitute a large
enough proportion of the diet

1158
00:51:17,220 --> 00:51:20,070
to compromise the dietary
requirement for thiamine.

1159
00:51:20,070 --> 00:51:22,320
And this is coming from the
World Health Organization.

1160
00:51:22,320 --> 00:51:23,862
If there's any
organization you think

1161
00:51:23,862 --> 00:51:26,880
you can trust about health
everywhere, it's the WHO,

1162
00:51:26,880 --> 00:51:29,200
it's these guys.

1163
00:51:29,200 --> 00:51:32,510
And I don't think we have time
for more of the conclusions,

1164
00:51:32,510 --> 00:51:37,030
however I will post this
document up to the learning

1165
00:51:37,030 --> 00:51:38,590
module site so you
guys can peruse

1166
00:51:38,590 --> 00:51:40,900
at your leisure along
with the bookmarks,

1167
00:51:40,900 --> 00:51:42,917
unless I've done it already.

1168
00:51:42,917 --> 00:51:45,250
Want to open it up the last
two minutes to any questions

1169
00:51:45,250 --> 00:51:47,320
you guys may have about
anything, including

1170
00:51:47,320 --> 00:51:50,080
final logistics, how it's
going to all come down,

1171
00:51:50,080 --> 00:51:53,105
the review session on Friday,
whatever you guys want.

1172
00:51:53,105 --> 00:51:55,230
AUDIENCE: So the review is
9:00 to 10:00 on Friday?

1173
00:51:55,230 --> 00:51:55,720
MICHAEL SHORT: Yep.

1174
00:51:55,720 --> 00:51:57,310
The review is 9:00
to 10:00 or 10:30,

1175
00:51:57,310 --> 00:51:58,870
whenever we finish on Friday.

1176
00:51:58,870 --> 00:52:00,760
I'll email out with a
room once I secure one.

1177
00:52:03,630 --> 00:52:04,130
Yeah?

1178
00:52:04,130 --> 00:52:07,306
AUDIENCE: Where do they
usually do food irradiation?

1179
00:52:07,306 --> 00:52:09,858
MICHAEL SHORT: There are
gamma irradiation facilities

1180
00:52:09,858 --> 00:52:12,025
where they've got these
cobalt 60 or cesium sources.

1181
00:52:15,520 --> 00:52:18,340
No, this would be
processing centers.

1182
00:52:18,340 --> 00:52:21,670
Yeah, I mean you
can't normally own

1183
00:52:21,670 --> 00:52:23,530
one of these giant
cobalt sources so.

1184
00:52:23,530 --> 00:52:25,540
These would be specialized
processing centers.

1185
00:52:25,540 --> 00:52:25,900
Yeah?

1186
00:52:25,900 --> 00:52:27,275
AUDIENCE: So is
this usually only

1187
00:52:27,275 --> 00:52:30,785
done for foods coming
in the US from outside?

1188
00:52:30,785 --> 00:52:31,660
MICHAEL SHORT: Oh no.

1189
00:52:31,660 --> 00:52:34,202
It can be done for foods grown
within and for the consumption

1190
00:52:34,202 --> 00:52:35,320
in the US too.

1191
00:52:35,320 --> 00:52:38,290
If you want to extend its shelf
life by small or large amounts

1192
00:52:38,290 --> 00:52:40,240
you can do it for
anything, but there

1193
00:52:40,240 --> 00:52:42,310
are a number of different
types of produce

1194
00:52:42,310 --> 00:52:45,755
that can only be imported
because of food irradiation.

1195
00:52:45,755 --> 00:52:47,380
One of these that I
was delighted about

1196
00:52:47,380 --> 00:52:50,430
was mangosteens from Thailand.

1197
00:52:50,430 --> 00:52:52,950
Mangosteens probably
almost no one here

1198
00:52:52,950 --> 00:52:54,300
has ever even heard of or seen.

1199
00:52:54,300 --> 00:52:57,420
I'm surprised anyone has.

1200
00:52:57,420 --> 00:52:59,400
OK, wow, two, that's a record.

1201
00:52:59,400 --> 00:53:01,860
They're usually only found
in South or Southeast Asia.

1202
00:53:01,860 --> 00:53:03,810
They don't tend
to last very long

1203
00:53:03,810 --> 00:53:05,850
and they tend to be
riddled with parasites.

1204
00:53:05,850 --> 00:53:08,310
But one time out of two that
I've opened up a mangosteen,

1205
00:53:08,310 --> 00:53:10,350
a whole bunch of bugs
started crawling out.

1206
00:53:10,350 --> 00:53:12,270
You'd imagine that
the US doesn't

1207
00:53:12,270 --> 00:53:14,710
want that imported into here.

1208
00:53:14,710 --> 00:53:18,130
But in 2005 Thailand started
irradiating their mangosteens.

1209
00:53:18,130 --> 00:53:20,380
They were approved for
sale in this country

1210
00:53:20,380 --> 00:53:23,520
and you can find them at H
Mart now down the street.

1211
00:53:23,520 --> 00:53:27,420
Even food from Hawaii has to
be irradiated for consumption

1212
00:53:27,420 --> 00:53:29,780
in the continental US.

1213
00:53:29,780 --> 00:53:32,680
Why do you guys think that is?

1214
00:53:32,680 --> 00:53:34,338
AUDIENCE: Human species.

1215
00:53:34,338 --> 00:53:35,880
MICHAEL SHORT:
According to the USDA,

1216
00:53:35,880 --> 00:53:39,150
Hawaii is effectively
a different country

1217
00:53:39,150 --> 00:53:40,860
when it comes to the
sorts of parasites

1218
00:53:40,860 --> 00:53:42,480
you'd find in the food.

1219
00:53:42,480 --> 00:53:44,820
It is a part of the US, but
it is not agriculturally

1220
00:53:44,820 --> 00:53:46,680
a part of the continental US.

1221
00:53:46,680 --> 00:53:48,930
It's got its own unique
parasites and pathogens

1222
00:53:48,930 --> 00:53:50,910
and organisms and critters.

1223
00:53:50,910 --> 00:53:52,590
So a lot of things
coming from Hawaii

1224
00:53:52,590 --> 00:53:54,630
have to be irradiated
for consumption

1225
00:53:54,630 --> 00:53:57,530
in the continental US.

1226
00:53:57,530 --> 00:54:00,810
So yeah, food irradiation
helps food commerce go around.

1227
00:54:00,810 --> 00:54:02,150
Any other questions?

1228
00:54:05,150 --> 00:54:06,242
Yeah?

1229
00:54:06,242 --> 00:54:07,310
No, it's you.

1230
00:54:07,310 --> 00:54:09,835
AUDIENCE: What percentage of
food actually gets irradiated?

1231
00:54:09,835 --> 00:54:11,960
MICHAEL SHORT: I don't know
what percentage of food

1232
00:54:11,960 --> 00:54:12,990
gets irradiated.

1233
00:54:12,990 --> 00:54:14,600
It especially
depend on the type.

1234
00:54:14,600 --> 00:54:16,280
There's some things
that don't need it.

1235
00:54:16,280 --> 00:54:18,795
There's some things
that do need it.

1236
00:54:18,795 --> 00:54:21,170
I'd wager a guess to say that
more imports get irradiated

1237
00:54:21,170 --> 00:54:25,690
than domestic consumption stuff,
but I don't know that for sure.