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NATHAN: Yo.

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My name is Nathan.

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Today I'm going to talk to
you about food preservation.

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So everyone has food.

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We eat it.

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Got to survive, and you
can't eat it forever.

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It's going to go bad.

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And so I've got
these two examples.

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I got this nice
orange, pretty vibrant,

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but it's a bit squishy.

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I don't think I'd
want to eat it.

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I've also got these crackers.

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They were left out for a
couple weeks, but I don't know.

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They're still pretty crunchy.

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And I think I'd eat them.

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In fact, I did.

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So what exactly is it that
causes food to go bad?

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And the answer to that is
usually fungus and bacteria.

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So first off, let's think
about what we're up against.

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Where are fungus and bacteria?

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And the answer is everywhere.

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So when we're talking
about fungus and bacteria,

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they can enter the food's
system at pretty much any point

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along the way.

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You know, when you have
a nice animal sitting

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along munching its grass,
it can get in at that point.

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And they'll be carried along to
the meat if you're eating meat.

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It can get on when
you're processing food,

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when it's on a con-- you
know, in large factory group

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settings.

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And of course, when you're
preparing food or eating it,

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it's going to get off
your grubby, little hands.

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So that's what it is.

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How does it survive?

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What does it need?

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And that's going
to be same as us.

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It just needs food, water,
and oxygen. Pretty simple, so

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how do you deal with that?

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There's no sort of
like special thing

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to survive that you can
easily take advantage of.

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Well, there's two basic ideas.

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First, you want to
slow down and then

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try to stop its beh--
you know, its activity.

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And the second is you want to
kill the fungus or bacteria.

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And there's a number
of ways to do these.

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So you can refrigerate
and freeze an item.

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It slows down activity.

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You generally want to keep
it in the fridge about-- just

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like a smudge around like
35 degrees Fahrenheit.

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And if you-- or in
the freezer, you

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want it just below freezing.

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You can dehydrate or
freeze dry something,

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and that does a pretty good
job of inhibiting activity.

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You can salt something,
which can, in fact, both kill

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and inhibit activity.

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You can pickle something.

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You can pasteurize it.

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You can can it.

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You can radiate it, which
works fantastically.

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But people don't
like nuclear stuff.

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You can ferment it.

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You can carbonate it.

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But by and large, in American
society, we like chemicals.

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So most of the food
you're going to eat

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isn't, like fresh produce,
is going to, in fact,

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have chemical preserves,
preservation in it.

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So what are the-- there is
three main ways to do this.

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You can have an
antimicrobial approach.

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You can have an antioxidant.

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And you can working its enzymes.

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The first one is pretty simple.

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You're just going to try
to kill the small microbes,

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the bacteria, the fungus.

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The second one, you're going
to, as the name would imply,

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antioxidant.

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You're basically going to
try to prevent these things

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from breaking down fats
and lipids by having

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a reducing agent.

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And last thing is
when you're talking

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about going against
enzymes is basically

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in some things like
food in particular,

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when an item is ripe, these
different enzymes start coming

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up, like an ascorbic
acid in apples,

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and basically what you try
to do is counteract these.

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So within things that
perform these functions

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is four main things that
use-- get used a lot.

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First, you have sulfides,
which do everything

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perfectly, or pretty well.

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But unfortunately, some
people are allergic,

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so you don't see
it in everything.

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Most commonly you're going
to see them in dried fruit ,

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kind of potatoes,
starchy things.

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You also have propionates,
which tend to be more

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for like things like bread.

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Or they also feed it
to a lot of animals.

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So to kill-- prevent them
from getting infections

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and all these things.

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And what that mainly
does is kills bacteria

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and especially fungus and
can keep things like bread

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more fresh.

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You have benzoates,
which are mainly

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for-- which basically just
kill the fungi or bacteria.

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But they tend to work at a
lower pH, so when it's acidic.

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And so often you'll
see those in things

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like fruit juices or carbonated
beverages or sparkling things

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or-- and vinegar-based
solutions.

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So that's where you see that.

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The last one, which is getting
to the meat of the topic,

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are nitrates and nitrites.

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And mainly you see
those as antimicrobials

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and as antioxidants.

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And you will see them
in hams, cured items.

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You know, if you're getting
any sort of frozen meat,

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that's going to have nitrates,
which are wonderful except when

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they react with amino acid.

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They can possibly
sometimes lead to cancer.

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They have some
carcinogenic links.

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But those are the
main ways that you're

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going to be able to have a nice,
fresh cracker versus a squishy

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old orange that had
nothing done to it.

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If you're interested,
the crackers

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have in them something that's
called sodium bisulfite,

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and it makes it nice and tasty.