I know I said I’d talk about sautéing today but I left out a little information yesterday that I’d like to cover before we move on… the effects of cooking. To fully understand how to cook, I think it’s important to understand what’s happening to your food during the process. There’s a whole lot more culinary geek talk today but I think you’ll find it interesting. It will bring more clarity to why we use so many different cooking techniques and how they give different results to our food. Cooking is indeed a science and understanding the science behind it can only make us more successful in the kitchen.
Nutrients in Food
All foods are made up of a combination of essential nutrients: proteins, carbohydrates (starches and sugars), water, lipids (fat and cholesterol), minerals, and vitamins. Most foods have at least a trace of each nutrient and all nutrients react differently to heat.
Going a step further, each nutrient reacts differently to each type of heat. When you multiply the number of possible combination of nutrients that makes up each food by the number of cooking techniques (like the 15 in yesterday’s intro), you have an infinite amount of possible outcomes to cooking your food. Fortunately we don’t have to test out all those outcomes ourselves. As a society, we have hundreds of years of culinary trial and error to fall back on. Over the centuries, we’ve learned that fish is better poached than boiled and bottom round is better braised than grilled. But why?
I’ll begin my attempt at answering that question today by talking about how each nutrient responds to heat. Then tomorrow (I promise) I’ll start chipping away at the answer as I go more in-depth with each cooking technique.
The Effects of Cooking on Nutrients
So we know that each nutrient responds differently to heat but let’s take a look at just how they react.
Proteins are large, complex molecules that are found in all living cells (plants and animals). When energy (or heat) is applied to proteins they shrink, lose moisture, and become firm in a process called coagulation. Coagulation is the irreversible transformation of proteins from a liquid or semi-liquid state to a solid state. You’ve seen a steak firm up when cooked but think about what happens when you fry an egg… the liquid white and yolk both turn to a solid. The same thing happens to the wheat proteins (also known as gluten) in bread; the mixture of gluten and liquid goes from a semi-liquid to a solid.
Starches are complex carbohydrates found in plants and grains like potatoes, wheat, rice, and corn. When a mixture of starch and liquid is heated, the starch granules absorb water, causing them to swell and soften. As the starch granules cook, they soften enough to absorb water and hold the liquid in place so that the dish appears and feels thicker. This process is known as gelatinization and can occur anywhere between 150DEGREESF – 212DEGREESF, depending on the type of starch. Examples of gelatinization are: thickening a sauce with cornstarch, potatoes boiled in water, and a cake… the starch (flour) absorbs the liquids in the batter and thickens and swells while cooking in the oven.
Sugars are simple carbohydrates used by all plants and animals to store energy. As sugars cook, they gradually turn brown and change flavor in a process called caramelization. Caramelized sugar is used in a wide range of applications including sauces, candies, and unlimited desserts.
Sucrose (basic sugar) begins to brown at about 338°F. The sugars that naturally occur in foods (maltose, lactose, and fructose) also caramelize but at different temperatures. Because most caramelization occurs at extremely high temperatures, usually only the outside of foods will caramelize; the sugar molecules on the inside of food just doesn’t get hot enough. Caramelization also only occurs in dry-heat cooking methods since water can’t be heated above its boiling point of 212°F. Foods cooked in dry-heat methods, especially in the presence of fat, can easily reach the necessary temperature for caramelization or browning.
All foods contain water. In fact, most foods contain more water than you probably imagine… at least 75%. (Check out this list of foods and their water content from the University of Kentucky.) You already know that water evaporates when it’s heated so it only makes sense that the water in food evaporate when cooked. And that’s exactly what happens. That’s why your pork chop has the consistency of cardboard when you cook it to 185°F. And why your cake turns to a powder when it’s baked too long. The most important reason for cooking your food to the proper temperature is to protect its water content. The more water that evaporates from your food, the less appetizing it is.
(By the way, that doesn’t make the opposite true… boiling your food in water for extended periods does not make it more palatable. Blech.)
Fat is an energy source for the plants and animals in which they’re stored. Fats are smooth, greasy substances and do not dissolve in water. Their texture varies from firm to liquid (as in oils). Fats melt when heated. They slowly soften before they liquefy. Unlike water, fats do not evaporate. Because fats can withstand high temperatures without burning, they’re often used as a cooking medium to brown foods. However, not all fats handle high temperatures well so make sure you know the smoke point of your fat before cooking it at high temperatures. (More on selecting fats here.
The Maillard Reaction
Foods that are rich in proteins or starches develop a rich color when cooked at high temperatures, similar to caramelization. The process for browning proteins or starches is known as the Maillard (my-YAR) Reaction, named after Louis-Camille Maillard, an early 20th century scientist who first noticed the relationship between amino acids and sugars.
People often use the terms caramelization and Maillard reaction interchangeably but they’re definitely not the same thing. The Maillard reaction is not a single reaction, but a complex series of reactions between amino acids and reducing sugars, usually at high temperatures. In the process, hundreds of different flavor compounds are created. Maillard reactions are important in baking, frying or otherwise heating of nearly all foods. Maillard reactions are (partly) responsible for the flavor of bread, cookies, cakes, meat, beer, chocolate, popcorn, and cooked rice, just to name a few. In many cases, such as in coffee, the flavor is a combination of Maillard reactions and caramelization. However, caramelization only takes place above 338°F, whereas Maillard reactions already occur at room temperature.
There are so many more variables that go into how food reacts to heat and we’ll learn all about them as go through this series. Next up: Sautéing.