### Food and Science

#### Overview of this Week's Science Concepts

###### Below is a brief introduction to molecules.
• Atoms are the smaller units that make up molecules. There are over a hundred types of elements, but only a handful are used in food: hydrogen, oxygen, carbon, and nitrogen are the most common.
• Water is the most prevalent molecule in food. It consists of two hydrogen atoms attached to one oxygen atom. One useful way of categorizing molecules is how they interact with water; they can be attracted to water (hydrophilic) or be repelled by it (hydrophobic).
• Many of the large molecules in food are chains of smaller units. The chains are called polymers and the smaller units are called monomers.
• Carbohydrates can be monomers, like glucose and fructose. These can form dimers, like sucrose, or longer polymers, like starches, pectins, and gums. These are typically hydrophilic
• Proteins are polymers of amino acids. Some of these amino acids are hydrophobic, some are hydrophilic, and some are neither. The protein folds in a way so that most of the hydrophilic parts are on the outside and the hydrophobic ones are on the inside.
• Fats or oils consist of three fatty acids attached to a glycerol backbone, so they are called triglycerides. The fatty acids can be saturated (straight) or unsatured (bent, due to a double bond in the carbon chain). They are typically hydrophobic.

#### Equation of the Week

###### Each week in the class has an equation that connects the scientific concept to the culinary applications. The equation this week allows you to convert between the number of molecules and the amount of an ingredient in a recipe.
• Since there are so many molecules in any amount of an ingredient used in a recipe, scientists use Avogadro's Number, NA, which is equal to:

$$N_A = 6.022 x 10^{23}$$

One mole of a material has Avogadro's number of molecules.

• Using the molecular weight, we can calculate the molarity (moles per liter) of ingredients in a recipe, such as the salt in a soup. For this case, we used the molecular weigh of salt (58.44 g/mol). If there are g of salt dissolved in L of water, then then concentration is molar.

#### Beyond the Lecture

Large molecules that interact with water, called hydrocolloids by chefs, have changed what is possible with cooking. Most of these are polysaccharides.

You can read more from the Cooking Issues Hydrocolloids Primer or the Kyhmos Hydrocolloid Recipe Collection, in addition to later lectures in this series.