Measuring and Weighing

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.

In creating recipes so other people can reproduce your culinary masterpieces, careful weighing and measuring is also important.  But when you're just cooking up some breakfast, it is more important to know why the ingredients are there, and why certain processes are used.  This lets you create and adjust the food on the fly, substituting some ingredients you have for some you don't, or using up things from the back of the refrigerator before they go bad.

Variations in recipes

We can get a feel for how important measuring is by comparing recipes.  Suppose we find ten recipes for homemade cupcakes, and compare the ratios of flour and sugar in them:

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 in simple cupcake recipes.  A good cook can feel free to vary the amount of sugar in the recipe to suit either taste or what will accompany the cake, such as icing, or bits of fruit in the batter.

Why sifted flour?

Many 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 will be more important.

Recipes used to call for sifting flour.  Flour was something that often had lumps, bits of millstone, or insects in it, and sifting was important.  Other reasons have been suggested for sifting, such as aeration, or mixing dry ingredients, but these things can easily be done with a whisk in a bowl, and the bother of sifting would not be worth it if this were the main reason.

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, and then call for 3 eggs, without specifying the weight of the eggs.  Eggs vary in weight, and most recipes don't even specify the size of the egg in small, medium, large, or extra large.  The reason is that it really doesn't matter a lot.  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 their 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 in the water, tells how much sugar, alcohol, and water are in the mix at any given time.  Density can also tell you how fresh your eggs are.  Place the egg in water, and dissolve measured amounts of salt in the water until the egg floats.  Bad eggs will float right away.

You may have noticed at a party that some cans of soda in a tub of ice water float, and others sink.  This is density, telling you that the sodas with sugar in them are at the bottom, and the diet sodas are at the top.  An interesting experiment to try is to place a diet soda can in a glass of water large enough to float it, and then place a small plastic cup on top.  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, and probably more.

Another place where density comes into play in the kitchen is in making hard boiled eggs. The yolk of the 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 will float to the top of the egg, and thus be off-center when the egg is cut in half for devilled eggs, or sliced into a salad.

To keep the yolk centered, the eggs must be turned while being cooked, so that the yolk will not end up close to 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 U.S.) 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.

We know that proteins and carbohydrates have about 4 calories per gram, and fat has about 9.  We can separate the ingredients by whether they are fats or not, and weigh them, and then multiply.  Or we 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 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 we get 3.5 calories per gram.

Beef jerky has 116 calories in 28 grams, or 4 calories per gram.  Pork sausage has 95 calories in 28 grams, or 3.4 calories per gram.  Air popped popcorn has 31 calories in 8 grams, or 3.8 calories per gram.  Butter has 70 calories in 10 grams, or 7 calories per gram.  Bacon has 50 calories in 12 grams, or 4 calories per gram.  Butter-cream frosting has 100 calories in 26 grams, or 3.8 calories per gram.  Enriched flour has 455 calories in 125 grams, or 3.6 calories per gram.  Whole wheat bread has 70 calories in 28 grams, or 2.5 calories per gram. A steak has about 2 calories per gram.

What we see is that until we get to something like pure butter, most processed foods have between 3 and a half 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 1300 to 1800 calories per pound.  Put your whole meal on a plate, and weigh it.  If you don't like what the scale says the next morning, put less on the plate today.