What is kitchen chemistry? Chemistry Calendar, November: Food

Pretty much every aspect of cooking is like a chemical experiment.
From storing our ingredients, to mixing them in the right proportions,
or heating and cooling our mixtures to a specific temperature.
Not to forget all the biochemical reactions taking place in our bodies
as our bodies make use of the food that we eat and drink.
But change one ingredient in any chemical experiment
and you might end up with an undiscovered success.
Or a disaster…
Yes, that might happen sometimes.
But let’s do this.
Let’s cook up something good and take a look at some of the chemical reactions
taking place during this process.
Are you okay?

So all our ingredients here play important roles in the chemical reactions
to make something tasty.
Let’s take yeast here for example.
Why do we add it?
Well, to get the dough to rise, right?
But what is the chemical reaction that makes this happen?

Well, baking without yeast would not be the same.
Yeast is in fact a living fungus that uses the energy in sugar to grow and multiply.
And what it does is that it converts sugar, together with oxygen, to energy.
And the waste products are water and carbon dioxide,
which is the same gas that we have in soft drinks.
And the reaction looks like this.

A lot of times when we do chemical experiments,
the rate of the reaction is dependent on temperature,
and the yeast here is a good example of this.
When kept in the cold fridge, the yeast's activity is very low
and the yeast cells won't grow.
But bring the temperature up too much and the heat will also interrupt the reaction,
or kill the yeast cells.
And this happens in the oven.
The perfect temperature may vary dependent on different reactions,
but for yeast cells that perfect reaction temperature is around 30 degrees Celsius.
But for scientists, yeast has much greater importance than most people know.
The same type of yeast has been used by researchers for a long time
to study and understand the components of our own human cells.
And now, scientists have even figured out that yeast can also be used to
produce things for us, like proteins and even plastics!

Okay so these ones are ready for the oven.
And in here, in the heat, there are other chemical reactions taking over.

You probably already know that when we increase the heat like this,
the food can change color.
And reactions responsible for this change
are actually also the reactions giving the food its specific smell and taste.
And scientists usually call these reactions the Maillard reaction.
The Maillard reaction is a collective name for a group of reactions
that are all responsible for color, odor and flavor in food.
But they are not actually fully understood,
but we know that amino acids in protein react with carbonyl groups,
that can be found in for example sugar,
and form these many different flavor and odor molecules.
The Maillard reactions happen in most of our food when we cook or bake it.
Because it is at these high temperatures that the Maillard reactions
are doing their magic the best.

But even after we're done, an understanding of chemistry
can also help us explain how to prevent our food from getting spoiled.
One common way for our food to get spoiled is through oxidation.
And that reaction is very similar to the one where yeast used oxygen
to break down sugar.
Oxidation can pretty easily be demonstrated with an apple.
When an apple is cut, a colorless enzyme that is found in the cells of the apple
reacts with oxygen in the air, resulting in the production of
a brown melanin pigment, a first sign that the fruit is starting to go bad.
And this can also affect the nutritional value of the food.
Because what it comes down to is that we eat to live, right?
And what happens in our bodies after we’ve eaten
is something food scientists are especially interested in.

My name is Nathalie Scheers.
I am a researcher at Food Science at Chalmers University of Technology.
Here at Food Science we do a lot of different things.
Some of the research is about studying bioavailability
of for instance minerals or bioactive compounds.
Bioavailability means the fraction of the nutrient absorbed
compared to the whole nutrient that you ingest.
Nathalie tells us about some of the projects at Food Science
where researchers study many of the factors
involved in how the nutrients in food are absorbed by the body.
And they even have an artificial stomach, called TIM, to study it!
The chemical composition of the food plays a big role in this, as well as pH,
passage time through the intestine and the status of the absorbing cells.
So different compounds are absorbed in different parts of the bowel.
So that’s why it is important to know the whole process.

So you see that saying food is chemistry, is definitely no exaggeration.
And there are many chemical reactions
involved before the food ends up on our plate.
Not to mention all the biochemical reactions happening inside our bodies
after we’ve eaten something.
As always, remember that Chemistry is all around You!
But don’t eat in the lab!