There’s nothing quite like a quiet night on the
couch, digging into a tub of delicious ice cream.
Like so much else, engineering has a lot to
contribute when it comes to crafting that
perfect scoop.
In fact, the ice cream-making process has
many of the same challenges as other food
production.
Getting ingredients from the field to your
fork might seem pretty straightforward.
But there’s actually a whole discipline
dedicated to production, sanitation, transportation,
and, of course, how it all tastes.
It’s called food engineering.
And the methods and techniques are every
bit as high tech as fields like aerospace or
nanomaterial engineering!
So there’s some food for thought.
[Theme Music]
It’s no surprise that a lot of effort goes
into maintaining the systems that make food,
because everyone needs to eat.
This is a place where engineers can make a big
impact, and it’s only going to become more important
as the human population continues to grow.
Whether it’s ice cream or something else,
engineering what we eat comes with a unique
set of challenges.
Unlike a steel beam or a semiconductor, food
tends to be perishable – in other words, it spoils!
And while people tend to be picky about what
they eat, microbes like bacteria are much less fussy.
They might already be in food, or they can
easily find their way in through contaminated
surfaces or the air.
And lots of those microbes love eating what
we love eating.
That’s not always bad thing.
Foods like blue cheese are purposely
cultivated with certain kinds of bacteria to
produce their distinctive flavor.
But most of the time, bacteria or viruses
in your food are not good news.
If the wrong kinds of microbes are growing
on last week’s pizza, odds are good that it will
have a pretty nasty effect on your stomach.
It could even lead to food poisoning!
If food sits around longer, contamination
becomes more likely.
So time is of the essence in food engineering!
From the time the ingredients are harvested to
the moment the final product ends up in your bowl,
there are lots of ways for contaminants to get
into the mix and start causing problems.
Exposing food to too much air, light, or the
wrong temperature can also have adverse effects.
A container of milk left on your porch in
the sun too long will probably end up tasting
strange.
So engineers have to carefully control these
aspects of food production that affect how easily
bacteria can survive and how the food tastes.
Accomplishing all this requires some of the
other fields of engineering we’ve explored so far.
Especially in the case of ice cream, our old
friend thermodynamics comes into play.
To create cream in the first place, you have
to separate it from raw milk.
One way of doing this is with a centrifuge.
Because of the difference in density between cream
and the rest of the milk, the cream ends up farther from
the axis of rotation in a spinning vessel,
much like how swinging a pendulum in
circles draws the heavier bit outwards.
That cream can then be channeled away and
collected.
Of course, other flavor-specific ingredients
might require completely different production
techniques.
Consider the raisins you’d need for a batch
of rum and raisin ice cream.
As far back as ancient Rome, food production
techniques took advantage of sunlight and
wind to dry out fruits.
Less water meant the fruits wouldn’t spoil
as quickly.
Thousands of years later, the process hasn’t
changed an awful lot!
Since the Sun is a readily available source
of heat, many raisins are still produced by
leaving grapes out to dry.
And since the sugar stays behind as they lose
water, raisins are sweet.
No matter what ingredients you need for an
ice cream flavor, though, you need to mix
them in large batches.
Process control plays an important role in governing the
ratio of the ingredients and maintaining the machinery
that transports them from one place to another.
You’ll also need fluid mechanics, since
the ingredients of mixtures like ice cream
or cake batter are often in liquid form.
You can use some of the same tools that might
transport other liquids like petrol, but, again,
everything needs to be sterile.
And you also need to consider the materials
your equipment is made of.
For example, microbes don’t grow well on
copper surfaces, so you might think that would
be great for preparing food.
But running a creamy mixture through a copper
pipe might introduce bits of metal into the mixture.
At best, it just ruins the taste.
But at worst, it could lead to heavy metal
poisoning!
Stainless steel, on the other hand, is particularly
resistant to corrosion and doesn’t lose a lot of
material to the mixture.
So say you have safe equipment to move your
ingredients around.
Next, the ice cream mixture, as well as flavor-specific
ingredients like raisins or vanilla, will probably need
sugar and emulsifiers to give it just the right texture.
In the ice cream production process, everything
is combined in a tank, but it doesn’t automatically
mix evenly.
To do that, you need to pass everything through
what’s called a homogenizer.
A homogenizer forces a fluid under high pressure
through a small opening.
That squeezing breaks down large chunks into
smaller particles that are spread out more
evenly for a smoother mixture.
This mix of different ingredients makes the
ice cream more viscous than cream alone.
And since the fluid is thicker, heat will
flow through it rather differently than before.
That’s quite important for what comes next:
pasteurization.
Pasteurization was invented by French biologist
Louis Pasteur.
It involves heating foods, such as dairy
products, and then quickly cooling them to kill
off some of the bacteria.
The resulting products then stay fresher for
longer.
Because pasteurization involves a transfer
of heat to the mixture,
the ice cream’s viscosity has to be taken into
consideration when designing the machinery
that efficiently heats it up.
In the case of ice cream, you have two different
options.
One way is to apply a high amount of heat
for about half a minute.
Or sometimes, large tanks can be heated at
a lower temperature for a longer period of time.
That changes the chemical nature of some of the
ingredients, like caramelizing the sugar for example.
It’s up to the manufacturer whether or not
they want that change in taste!
Once pasteurization is done, you need to bring
the ice cream’s temperature back down.
And, crucially, you have to find a way to
store it at that colder temperature.
Storage is a vital part of food engineering.
Because of the shelf life of most foods, maintaining
supply chains, which transport food between producers
and retailers, is a tricky business.
The clock is always ticking!
But the way you package it can buy time, which
changes depending on the food.
Bread has to be sealed in bags to avoid going
stale, while foods like chopped tomatoes are
best preserved in cans.
And the storage environment at every step
of the supply chain can also prolong the shelf life.
After pasteurisation, the best choice for your
ice cream is to quickly move it from one freezer
to the next until it’s ready to be eaten.
If it’s going into a soft-serve machine, it passes
through a single stage of refrigeration before filling
the tank of the machine as a thick, cold liquid.
Or you might want individual scoops in paper
cups, pint sized tubs for those long nights in, or
the five-gallon plastic bins used in restaurants.
Whatever you decide, once you’ve transferred
the product to its final packaging, it needs some
serious freezing.
For ice cream, there are two stages that take
place.
The first is to harden it and the second is
for storing it.
You might think anywhere below 0°C would
be fine.
After all, water freezes at that temperature,
so surely that’s enough to stop any food
from going off?
Unfortunately that’s not the case!
Depending on how soon it’s going to be
consumed, frozen foods need to be kept at
a particular temperature.
Frozen fruits, such as strawberries, can
have a different shelf life depending on the
temperature they’re frozen at.
-5°C might allow them to keep for a month,
but storing them at -25°C keeps them edible
for two and a half years!
As for ice cream, it needs to be kept
at a chilly -40° in storage.
Any trucks that transport it and the storage
facilities at the grocery store need to have 
a similar freezing capacity.
Blast freezers can achieve this by blowing cold air
over the contents inside the freezer, carrying away
even more heat than the kind you have at home.
But after all that, you can head to the store and pick
up a tub of your favorite ice cream flavor to store in
your own freezer, ready to comfort you when needed.
It really makes you appreciate the amount of work
that goes into that spoonful of cherry garcia.
Of course, food engineering is about more
than making desserts.
The world’s population is growing fast,
and the demand for healthy, nutritious food
will grow along with it.
Equipment such as freezers, mixing vats, and
packaging machines all need to be specially 
designed for handling different products.
The equipment needed for ice cream is
different than the stuff for packaging fresh
fruit, or dried foods like rice.
Not to mention the engineering efforts that
go into agriculture and supply chains.
To create and provide the foods we love, engineers will
have to find ways to scale up delivery and production.
All while ensuring that it remains free from
bacteria and still tastes delicious!
With a problem this big, even small improvements
can result in vast savings of time, money, and energy.
And that’s a vital step towards a happy
and well-fed world.
Your Nana would be proud.
In this episode, we looked at food engineering.
We explored how food’s capacity to spoil
makes it a unique challenge from an engineering
viewpoint.
We saw how many branches of engineering come
into play to process ingredients, ensure safety
for consumers, and package food,
as well as how thermodynamics is involved
in the different stages of food production.
I’ll see you next week when we explore the
world of geotechnical engineering.
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Crash Course Engineering is produced in association
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