The Chemistry of Cookery Trivia Quiz

Answer: The water in the raw meat is evaporated off.

Raw meats contain approximately 75% water, and heating the meat during cooking causes the water to turn to vapor, reducing the volume of the meat.

Answer: It was cooked too long or at too high heat.

When eggs are boiled too long, or at too-high temperatures, sulfur in the egg white combines with hydrogen in the water, forming hydrogen sulfite. This in turn reacts with the iron in the egg yolk to produce the greenish outer rim of the egg yolk (another consequence of too high heat/too long cooking is that the egg white turns rubbery).

The green layer is not harmful to consume, it just doesn't look good.

Answer: False

Popcorn kernels are encased in sealed hulls, through which water and air can't escape. Heating the kernels increases pressure inside the hulls, eventually causing them to burst open. Other grains-wheat, for example-have hulls that are porous, so they don't pop when heated.

Answer: Add a small amount of water to the sugar, and heat it gently on the stovetop until it turns light amber.

Caramelization occurs when sugar dissolved in water reaches a temperature of 340-350 degrees Fahrenheit. At this temperature, chemical changes occur that turn the sugar brown and syrupy. Its flavor changes as well, with the release of volatile chemicals from the sugar.

Some other fruits and vegetables can also be caramelized. Onions are probably the best-known of these, but carrots, apples and other foods can also undergo caramelization.

Answer: Mayonnaise

When you mix together two or more ingredients that ordinarily would not mix, it's called an emulsion. There are two kinds in cookery-temporary and permanent. A familiar example of a temporary emulsion is oil and vinegar. You can mix the two together vigorously, and they will remain together for a short time but pretty soon, they'll un-mix and have to be shaken up again.

Mayonnaise, a mixture of oil, vinegar and egg yolks, is probably the most well-known example of a permanent emulsion. The lecithin in the egg yolks is soluble in both oil-based and water-based substances, and combines with both to form the permanent emulsion. Hollandaise sauce is another common permanent emulsion.

Answer: Baked items start out amorphous and develop a definite shape during baking.

One of the ways to tell if the baking process is complete is to touch the item you are cooking. If it's firm, chances are it's done or very close to being done. If it feels at all liquid, it needs further baking. Liquids are amorphous, solids are not.

Answer: Honey contains low concentrations of hydrogen peroxide.

Interestingly, honey does contain small concentrations of hydrogen peroxide. That, along with a few of its other properties, make honey a good remedy for treating infections. There is some evidence that honey can be used to kill MRSA, a staphylococcus bacterium that has become a major problem in health care facilities in the 21st century.

Answer: The protein in the eggs it contains coagulates.

The proteins in eggs "cook"-i.e., change texture, at very low temperatures (which is why you can-maybe-fry an egg on the sidewalk on blistering summer days, but no one ever grills a ribeye there). When heated over low heat, the egg proteins begin to coagulate before the custard reaches the boiling point.

The coagulation causes the custard to thicken. Good custard doesn't contain cornstarch.

Answer: Yeast interacts with sugar to ferment, causing gases to be released that leaven the bread.

In a warm, moist environment, such as baking bread dough, yeast combines with sugar to begin a process called anaerobic fermentation, producing alcohol and carbon dioxide. The latter is trapped by the gluten in the flour, causing the phenomenon of "rising", which consists of air pockets forming in the baking dough.

The yeast and the alcohol are both destroyed by heat--good thing, or the "staff of life" would likely cause inebriation!

Answer: A compound and a mixture

Mixtures consist of two or more ingredients are combined, but which each retain their original physical properties and can be separated back into individual ingredients by physical means like filtration. The amount of each ingredient in a mixture can vary.

Salsa is made by mixing tomatoes (or tomato puree) and various vegetables and spices. The ingredients, and the proportion of each ingredient, is up to the person making the salsa. No chemical transformation takes place during its creation. With enough time and effort, you could separate each of the ingredients in salsa.

Compounds, on the other hand, are composed of two or more ingredients that have undergone a chemical transformation together, and formed a new substance; the original properties of the ingredients are changed and cannot be retrieved through processes like filtration. In forming compounds, the amount of each ingredient is fixed and cannot vary.

Table salt is formed by a chemical transformation involving the two ingredients (elements) sodium and chlorine. Individually, sodium and chlorine are both poisonous. One atom of sodium combines with one atom of chlorine to form sodium chloride, which is not only not poisonous, but which is needed for good health and good food! While compounds can be changed back into their individual elements, this generally requires chemical operations and is more complex than separating the ingredients of mixtures.