Molecules, Moles, Flavour and pH: Science & Cooking
Due to the pandemic calamities that have unprecedentedly knocked on the door our planet, I- much like other privileged people am thankful to have internet and the safety of a house so I also enrolled in an online course. This particular one is called the Science & Cooking: From Haute Cuisine to Soft Matter Science (chemistry) on Harvard EdX. I’ve always been interested in knowing what I’ve been cooking- not just in terms of regional produce or history, but also on the scientific end of cooking. I know that acid is important in cooking and that it enhances its flavours but what is it exactly? What is in baking soda that makes me cakes so fluffy? What takes longer to cook- boiling or baking a potato and why? Why can I put my hand inside the oven but not in a pot of boiling water?
The course is divided into six modules: I thought I’d cover each one of these here so it would be a small revision for myself. The first one is called Molecules, Moles, Flavour and pH.
Food is made of Molecules: Fat, Carbohydrates and Sugar
When we think of food scientifically, food is made of molecules that combine together so that we can make something delicious to eat. Molecules like H2O, CO2 are all prevalent in everything we consume and these molecules themselves consist of atoms. Which are for example, in H2O, Hydrogen Oxygen. The main molecules that consist in food are Fat, Carbohydrates and Sugar.
Fats: Fats are the most common form of molecules that we eat. They are present in basic things like olive oil butter, meat. It has two types of features:
Fats can either be liquid or solid at room temperature
Fats do not dissolve in water
Carbohydrates: These consist of sugars: Glucose, Fructose, Sucrose and sugar chains that are starches: Amylose, Amylopectin.
Sugar has its own properties:
They are hard and hard to crush.
It dissolves in water
Starches has its own properties. They are polymers (chains of sugar molecules). If you take two sugars, glucose and sucrose and put them in long chains, thats startch.
Proteins: The red colour on steak comes from Hemoglobin which is protein. Milk has protein called casein. Albumin is a protein of egg. It has two features:
They dissolve in water: when you heat it up in water, you an get the protein to change conformation since it is an active molecule. It doesn’t keep the same shape as you cook it.
It’s a polymer like starch. The polymers tend to stick to each other and change th shape of many proteins.
Side Note: Often Nutritional Labels do not add the weight of water into the total serving which is why is when you calculate the total weight of serving it is incorrect.
There is a commonly accepted unit of what a large number of molecules should be called and its called the Atomic Mass Unit. It is 1/12 the mass of Carbon 12 and it is 1.66 x 10 –27 kilogram. The mass of carbon 12 is 12 times the AMU. How many atoms are there in 12grams of carbon 12 and that gives us the molecules which is called a mole that is 6.022×1023.
Note: there are so many calculations on this, I felt like I was back in 10th grade but doing more cooler chemistry than I had done back then.
Flavour is the overall experience we have in our sense when we eat food.
Types of flavour:
Taste: this is the input taste buds get from molecules in the food but it comes from the taste buds on the tongue. The bumps on your tongue are taste buds and interact with receptors that go through membrane channels that triggers a response to the brain. Sweet, salt, bitter all of these have different receptors.
Aroma: is more complicated as mulches go into the air and enter the retinal nasal create more nuanced flavours. If something is lemony, meaty or woody in taste it is because of the aroma molecules.
Touch: Hot flavour that we get from hot pepper is due to capsacin. It is a molecule that interacts with touch receptors.
Acid is the molecule that release a hydrogen ion. The measure of how strong an acid is the ability of the acid to give up a hyrodgen ion. Citric acid (lemon) give up hydrogen faster than sulphuric acid (batteries in car). Hydrogen ions are also protons.
pH = – log [H+]
we know that water is neutral through this formula:
pH = – log [H-7] = 7
If we look for the pH of other goods:
Red Wine Vinegar: 3.0
Coke is so acidic which is why there is so much sugar added to it, to neutralise it. Lemon and lime have an amount of citric acid which is about 0.3 moles per litre this is about 50 grams per litre. Orange juice has 0.005 moles per litre of citric acid. pH of lemon and lime is about 2 pH of orange juice is about 3.5 or 4 The difference between the pH of one can be ten fold the different between the concentration of hydrogen ions.
Baking Soda: Baking soda reacts with acids, so while using it you have to mix it with acid for example, buttermilk which will cause the cake to rise. When baking soda reacts with an acid its product is water and carbon dioxide(which makes the cake fluffy). It has a pH higher than 7.
Baking Powder: is baking soda plus an acid which is usually cream of tartar. It helps the cake become lighter, fluffier and more tender and creates more leavening.
Once these leaveners go into the oven they react with heat and activate.