When you're cooking, you're a chemist! Every time you follow or modify a recipe, you are experimenting with acids and bases, emulsions and suspensions, gels and foams. In your kitchen you denature proteins, crystallize compounds, react enzymes with substrates, and nurture desired microbial life while suppressing harmful bacteria and fungi. And unlike in a laboratory, you can eat your experiments to verify your hypotheses.
In Culinary Reactions, author Simon Quellen Field turns measuring cups, stovetop burners, and mixing bowls into graduated cylinders, Bunsen burners, and beakers. How does altering the ratio of flour, sugar, yeast, salt, butter, and water affect how high bread rises? Why is whipped cream made with nitrous oxide rather than the more common carbon dioxide? And why does Hollandaise sauce call for "clarified" butter? This easy-to-follow primer even includes recipes to demonstrate the concepts being discussed, including:
· Whipped Creamsicle Topping—a foam
· Cherry Dream Cheese—a protein gel
· Lemonade with Chameleon Eggs—an acid indicator
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In science, and especially in chemistry, careful weighing and measuring are important for reproducible results. If someone cannot reproduce your results, there is little point in doing the experiment.
For people to reproduce a culinary masterpiece, it is important to carefully weigh and measure according to a recipe. But when you’re just cooking up some breakfast, it is more important to know why the ingredients are used, and why certain processes are followed. With this knowledge, you create and adjust the food on the fly, substituting some ingredients you have for some you don’t, or use up things from the back of the refrigerator before they go bad.
Variations in Recipes
You can get a feel for how important measuring is by comparing recipes. Suppose you look at 10 recipes for homemade cupcakes and compare the ratios of flour and sugar in them:
Flour
Sugar
Ratio
1.5
1
150.00%
2.75
1.5
183.33%
2
1.5
133.33%
1.5
1
150.00%
2
2
100.00%
3
2
150.00%
2
2
100.00%
2.5
1
250.00%
3
2
150.00%
2.5
2
125.00%
Mean
149.17%
Standard Deviation
43.47%
The average cupcake has one and a half times as much flour as sugar. But some cupcakes have equal amounts, and some have two and a half times as much flour as sugar. The high standard deviation means that there is a lot of variation among simple cupcake recipes. A good cook can feel free to vary the amount of sugar in the recipe for taste or to compensate for what will accompany the cake, such as icing or bits of fruit in the batter.
Why Sifted Flour?
Some recipes list the ingredients by weight instead of volume. Some cooks swear by weighing everything, to get consistent results. When consistency of results is important, by all means, measure carefully. But when a little variation and creativity are called for, or when you are changing parts of the recipe for whatever reason, judgment and knowledge are more important.
Recipes once called for sifting flour. Flour was something that often had lumps, bits of millstone, or insects in it, so sifting was important. Other reasons have been suggested for sifting, such as aeration, or mixing dry ingredients, but a whisk in a bowl can accomplish both these tasks. The bother of sifting would not be worth it if either of these were the main reason.
So why sift? When ingredients are not weighed, the difference between a cup of flour and a cup of sifted flour can be significant. But a knowledgeable cook can use a bit less flour and avoid the time and mess of sifting.
It is interesting to look at recipes that are very careful to weigh out all of the ingredients yet then call for three eggs, without specifying the weight of the eggs. Eggs vary in weight, but most recipes don’t specify the size of the eggs as small, medium, large, extra large, or jumbo. The reason is that it really doesn’t matter too much. Whatever the size, the recipe is going to come out just fine. There is a lot of room for variation, and consistent results are usually not as important to the eater as they are to the creator of the recipe, who wants to protect his or her reputation for being reliable.
The best recipes will tell you what to look for in the processing of the food. Instead of giving a precise baking time, a cake will be tested for doneness with a toothpick or the press of a finger. In candy making, the initial amounts of sugar and water are not that important when you are cooking the mixture to a certain temperature or to “hard ball” stage, both of which are measures that tell the cook exactly what the ratios are during cooking.
Density and Good Eggs
In making wine or beer, the density of the mixture, measured by floating a little scale (called a hydrometer) in the water, 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.
You may have noticed at a party that some cans of soda in a tub of ice water float, while others sink. This is caused by density; sodas with sugar in them are at the bottom and the diet sodas are at the top. As an interesting experiment, place a diet soda can in a glass container large enough for it to float, then place a small plastic cup on top. Slowly fill the cup with sugar until the can sinks. You might be amazed at how much sugar it takes to sink the can. There is at least that much sugar in the sodas that sink, but probably more.
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.
Calorie Estimation
Some things are easy to measure. Not all cooks have kitchen scales, so many recipes (especially in the United States) call for easy volume measurements. But some things you might care about, such as how many calories are in the food you are making, might at first seem hard to measure at home.
But with a little thought, estimating calories isn’t that difficult.
As a general rule, proteins and carbohydrates have about 4 calories per gram, while fat has about 9. You can separate the ingredients by whether they are fats or not, weigh them, and then multiply. Or you can estimate by eye what percentage of the recipe is fats, and pick a number between 4 and 9 that matches the estimate. A little adjustment for water content, and you have a good guess at the number of calories in the food.
A Hostess Twinkie says on the label that it has 4.5 grams of fat (40.5 calories) and 27 grams of carbohydrates (108 calories) for a total of 148.5 calories. One Twinkie weighs 43 grams, and the label says it has 150 calories, so about 3.5 calories per gram.
Take a look at some popular foods:
Beefjerky: 116 calories in 28 grams, or 4 calories per gram
Pork sausage: 95 calories in 28 grams, or 3.4 calories per gram
Air-popped popcorn: 31 calories in 8 grams, or 3.8 calories per gram
Butter: 70 calories in l0 grams, or 7 calories per gram
Bacon: 50 calories in l2 grams, or 4 calories per gram
Buttercream frosting: 100 calories in 26 grams, or 3.8 calories per gram
Enriched flour: 455 calories in 125 grams, or 3.6 calories per gram
Whole wheat bread: 70 calories in 28 grams, or 2.5 calories per gram
A steak: about 2 calories per gram
What you see from the examples above is that until you get to something like pure butter, most processed foods have between 3½ to 4 calories per gram, about the same as pure sugar.
Celery has 0.16 calories per gram, an apple has 0.5 calories per gram, and a carrot has 0.4 calories per gram. These foods are mostly water. So eat fruits and vegetables to fill yourself up if you are watching your calories.
Steaks, chicken, pork chops—even those have fewer calories per gram than popcorn or bread. But within about a factor of two, you can simply weigh the food and figure 1,300 to 1,800 calories per pound. Put your whole meal on a plate and weigh it. If you don’t like what the bathroom scale says the next morning, put less on your plate today.
Of course, counting calories to control your weight assumes that your weight is simply a matter of balancing the number of calories you eat with the number of calories you burn. But your body already has mechanisms for doing that balancing. If you starve yourself, your body will stop burning as many calories. If you eat too much, your body will burn more. This is controlled by hormones in your body, the main one being insulin.
Insulin tells the fat cells to take in sugar from the blood. When there is too much sugar in the blood, extra insulin is produced to remove it, and thus extra fat is stored. Foods with high insulin indexes (foods that cause more insulin to be produced than other foods do) can upset the balance that keeps your calorie inputs and outputs matched. This is why low-carbohydrate diets seem to be effective in controlling weight. They prevent excess insulin from being produced and thus prevent extra fat from being stored.
There are many complex interactions in the body that affect the balance that controls fat production. Some are genetic, some are behavioral, some are environmental, and some are caused by infections or disease. Planning effective weight control for an individual will necessarily be an individual exercise, and one diet plan will not work for everyone. But it is important to understand that simply cutting calories or getting more exercise is not the whole story.
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FOAMS
Foams are fun. Marshmallows, meringues, cakes, whipped cream, cookies, ice cream—all of these are foams.
Foams are formed by several different processes. In many foams, such as whipped cr...
