The Science Of Cooking — Make It More Fun
September 11, 2019 at 6:09 p.m.
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Yeast (Saccharomyces cerevisiae) is also used to leaven bread (to make it rise). It is made up of minute one-cell fungi that rapidly multiply if given their favorite foods of sugar or starch in a moist environment. When the yeast cells feast on the sugar or starch that a yeast enzyme has converted to glucose (sugar), a chemical reaction takes place. The sugar ferments, and as a result, is converted into alcohol and carbon dioxide, along with trapped air and steam which leavens the bread.
Chemistry is also responsible for the taste of tomatoes. This time of year when they are so plentiful, it is wise not to refrigerate them. Tomatoes won’t be as aromatic and savory because cold hinders the conversion of the vegetable’s linolenic acid to Z-3 hexenel, the compound that accounts for much of the desirable ripe tomato scent and taste. Cold also reduces the volatility of molecules and therefore the number of Z-3 hexenel molecules that reach the olfactory receptors in the nose.
The density of a mixture is an important factor when cooking. Density is measured by floating a little scale (called a hydrometer) in the water, which tells how much sugar, alcohol, and water are in the mix at any given time. A density test can also tell you how fresh your eggs are. Place an egg in water, then dissolve measured amounts of salt into the water until the egg floats. A bad egg will float right away.
Another place where density comes into play in the kitchen is in making hard-boiled eggs. The yolk of an egg contains fats and oils and is thus less dense than the white of the egg. This means that if left to itself, the yolk inside will float to the top of the egg and thus be off-center when the egg is cut in half for deviled eggs or sliced into a salad. To keep the yolk centered, the eggs must be turned frequently while being cooked, keeping the yolk away from the shell. Since the white of the egg cooks on the outside first (where it is closer to the boiling water), the yolk that is turned often will not be able to get past the hardening white and will end up centered.
Other chemical reactions are involved in whipping creams and beating egg whites. In both of these processes proteins in the foam are first denatured, which, as the name implies, means that they are changed from their natural state. Proteins are made up of building blocks called amino acids. Some of these building blocks are attracted to water but avoid oils and fats. Others are attracted to oils and fats but are repelled by water.
In whipped egg whites, you get bubbles with a protein film. The water-loving parts stick into the water, and the water-avoiding parts stick into the air bubble. In whipped cream, you get big bubbles of air surrounded by a film of protein, surrounded by tiny globules of fat stuck to the fat-loving parts of the protein, connected to another film of protein that forms the wall of the next bubble.
Final thoughts
In essence, cooking provides a greater appreciation for science and makes it less of a chore. Science does the same for cooking. Try it some time.
Max Sherman is a medical writer and pharmacist retired from the medical device industry. He has taught college courses on regulatory and compliance issues at Ivy Tech, Grace College and Butler University. Sherman has an unquenchable thirst for knowledge on all levels. Eclectic Science, the title of his column, touches on famed doctors and scientists, human senses, aging, various diseases, and little-known facts about many species, including their contributions to scientific research. He can be reached by email at [email protected].
Yeast (Saccharomyces cerevisiae) is also used to leaven bread (to make it rise). It is made up of minute one-cell fungi that rapidly multiply if given their favorite foods of sugar or starch in a moist environment. When the yeast cells feast on the sugar or starch that a yeast enzyme has converted to glucose (sugar), a chemical reaction takes place. The sugar ferments, and as a result, is converted into alcohol and carbon dioxide, along with trapped air and steam which leavens the bread.
Chemistry is also responsible for the taste of tomatoes. This time of year when they are so plentiful, it is wise not to refrigerate them. Tomatoes won’t be as aromatic and savory because cold hinders the conversion of the vegetable’s linolenic acid to Z-3 hexenel, the compound that accounts for much of the desirable ripe tomato scent and taste. Cold also reduces the volatility of molecules and therefore the number of Z-3 hexenel molecules that reach the olfactory receptors in the nose.
The density of a mixture is an important factor when cooking. Density is measured by floating a little scale (called a hydrometer) in the water, which tells how much sugar, alcohol, and water are in the mix at any given time. A density test can also tell you how fresh your eggs are. Place an egg in water, then dissolve measured amounts of salt into the water until the egg floats. A bad egg will float right away.
Another place where density comes into play in the kitchen is in making hard-boiled eggs. The yolk of an egg contains fats and oils and is thus less dense than the white of the egg. This means that if left to itself, the yolk inside will float to the top of the egg and thus be off-center when the egg is cut in half for deviled eggs or sliced into a salad. To keep the yolk centered, the eggs must be turned frequently while being cooked, keeping the yolk away from the shell. Since the white of the egg cooks on the outside first (where it is closer to the boiling water), the yolk that is turned often will not be able to get past the hardening white and will end up centered.
Other chemical reactions are involved in whipping creams and beating egg whites. In both of these processes proteins in the foam are first denatured, which, as the name implies, means that they are changed from their natural state. Proteins are made up of building blocks called amino acids. Some of these building blocks are attracted to water but avoid oils and fats. Others are attracted to oils and fats but are repelled by water.
In whipped egg whites, you get bubbles with a protein film. The water-loving parts stick into the water, and the water-avoiding parts stick into the air bubble. In whipped cream, you get big bubbles of air surrounded by a film of protein, surrounded by tiny globules of fat stuck to the fat-loving parts of the protein, connected to another film of protein that forms the wall of the next bubble.
Final thoughts
In essence, cooking provides a greater appreciation for science and makes it less of a chore. Science does the same for cooking. Try it some time.
Max Sherman is a medical writer and pharmacist retired from the medical device industry. He has taught college courses on regulatory and compliance issues at Ivy Tech, Grace College and Butler University. Sherman has an unquenchable thirst for knowledge on all levels. Eclectic Science, the title of his column, touches on famed doctors and scientists, human senses, aging, various diseases, and little-known facts about many species, including their contributions to scientific research. He can be reached by email at [email protected].
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