The Components Of Milk
Milk is basically composed of milk fat, milk sugar which is known as lactose, and casein, which is the major milk protein. The fat content in milk is shaped into very small droplets that can be seen very well under a microscope. When milk is left to stand for a while, you can see the fat that will come to rest at the surface and forms a layer of cream. The kind of milk known as skim or skimmed milk is simply milk minus the milk fat. Centuries ago, farmers made skim milk by skimming off the cream layer of the milk by repeatedly dipping a dish with tiny holes into it.
The dish would slowly scoop up the cream while the holes drain the milk that might come with it. This process took a very long time to finish. In the year 1877, Gustav de Laval was a Swedish engineer who invented the Centrifugal Cream Separator. This machine is able to remove the cream from the milk by rapidly spinning the milk in a bowl. While spinning, the cream would pass through one spout while the skim milk passed out through another. This cut down a huge part of production time because there was no need to wait for the cream to settle at the surface of the milk. The milk by itself has 5 to 10 times less fat than its cream components. The cream, however, can be made a lot less rich by adding skimmed milk because it has very little fat. “Whipping” cream in the United States contains about 30 to 35% fat. “Table” or “coffee” cream contains about 18 to 20% fat while the cream called “half and half” contains the least fat with about 9 to 10%.
Cream has a rich look and a golden color that comes from carotene. When the sources of milk, like cows for instance, consume fresh green fodder such as spring pasture grass, the milk they produce becomes very rich in carotene. This component provides the pigment in milk fat. When consumed by the human body, the carotene is converted into vitamin A which is a very important nutrient.
Milk is rich in high-value protein and it has two kinds of protein: the casein and whey proteins. Casein comprises about 80% of the total protein in milk and is the basis of all cheese products, especially cottage cheese which is mostly Casein. Casein forms into a jellylike and lumpy mass that is called curd or clabber when the milk turns sour. The casein has other uses aside from food. It is used to make paint, sizing or paper-coating material, and is also a water-resistant adhesive. There are clothes made out of casein wool and many other things made of casein plastic.
Whey is the other protein found in milk. It is a pale, greenish-colored liquid that separates from casein. The green color is taken from vitamin B2 or Riboflavin. This milk component contains all of the milk sugar, some of the vitamins, and almost all the minerals of milk. The whey protein comprises the other 20% of the total milk protein. When milk is boiled and then allowed to stand for a few minutes, a layer on the surface is formed called the “skin” or “scum”. This layer is the very heat-sensitive whey proteins. When whey proteins change as they are heated, the taste of the milk changes also. This is the reason why the flavor of milk is different when it is heated to high temperatures or boiled.
The last of the basic milk components is lactose or milk sugar. Lactose is a special kind of sugar that is only found in milk. It is not as sweet as table sugar nor is it as easy to dissolve. Because it dissolves slowly, lactose is not as quickly digested as other common sugars. The milk becomes sour after a certain amount of time because the lactose is fermented by bacteria. These bacteria turn the lactose into lactic acid. The lactic acid produced makes the casein firm, giving it its curd like appearance and the milk’s sour taste. Milk is intentionally soured to make a variety of milk products such as cheese. Lactose, in its pure form, is a finely ground white powder that is used in medicines. This form of lactose has been used by many drug companies as a base for growing the antibiotic penicillin.