Full-fat fresh milk is the raw material source of cream and butter. Natural milk contains 3% ~ 4% fat and about 87% water. These fats are "oil in milk".
Arguably, oil and water are incompatible, but the fat in milk will not be layered, because they exist in milk as tiny fat globules, and there is a protein membrane outside the fat globules that can be "affinity" with water, helping the fat globules to be evenly suspended in whey. These small balls are very small, the diameter of which is only a few microns, and the small balls can directly pass through the intestinal mucosa, so the human body can easily digest and absorb the fat in milk.
According to the laws of physics, these small fat balls can scatter light and make milk milky white. The words "emulsification" and "emulsion" actually come from the white liquid produced by the fat globules of milk.
If the whole milk is centrifuged, the fat microspheres in the milk will float on the upper layer according to the different specific gravity. Separate them directly, and the product is called cream. Thin cream contains only 20%~30% fat, and the fat still exists in the form of fat balls, so thin cream is still white. Thin cream, also called cream for short, can be added to coffee and tea, and also used to make desserts and sweets. If it is used for fermentation, sour cream can be produced.
If milk or thin cream is stirred violently, just like when Tibetans and Mongolians "butter", the protein membrane of milk fat globules will rupture and milk fat will flow out of the globules.
Without protein's protection, fat and water can't be mixed together and are inevitably separated. As a result, the fat in the milk slowly floats up and gathers together. At the same time, because of the loss of the original "emulsion" structure, milk loses its milky white, and milk fat shows its original color-light yellow.
At this time, the upper layer of fat is separated, salt is added and the water is squeezed to remove it, which becomes the butter for daily consumption. Butter is also called "butter", but many people call it "cream", which sounds like thin cream, causing some confusion. The milk after fat removal is called skim milk, and the fat contained in it is reduced to about 0.5%.
Fat-soluble nutrients in milk all exist in milk fat, including vitamin A, vitamin D, vitamin K and carotene. Therefore, butter is an excellent source of vitamin AD. The yellow color of butter comes from carotene, because the grass and carrots eaten by cattle contain a lot of carotene.
However, because butter contains more than 85% fat, all kinds of water-soluble components in milk are basically separated and left in skim milk. Therefore, the contents of protein, lactose, vitamin B and calcium in butter are very low. Therefore, butter can't be used to supplement calcium, it is just a big piece of fat.
Anyone who has used butter knows that butter is solid and harder than lard. This means that the degree of fat saturation in milk is very high, and there are few unsaturated fatty acids and few essential fatty acids. Therefore, the nutritional value of cream is not high, and it is basically the same as butter. At the same time, cream also contains a small amount of cholesterol. If you drink a glass of milk, the amount of saturated fat and cholesterol is very small, so you can ignore it. If you want to eat food made of butter often, you should consider it properly. For example, cakes, cookies, cookies, buttered bread, etc., may bring a lot of saturated fat.
It can be seen that the whole milk contains the most comprehensive nutrients. The vitamin AD of skim milk is basically lost, while the butter that comes off contains a lot of saturated fat, cholesterol and vitamin AD, but it is not a good source of calcium and protein. The nutritional value of thin cream is between the two.
As for the so-called "whipped cream" used to make cakes, it has nothing to do with cream at all. Their main ingredient is plant creamer, which is actually a mixture of hydrogenated vegetable oil, starch hydrolysate, some protein ingredients and other food additives. It contains "trans fatty acids", its nutritional value is worse than butter, and it is easy to induce cardiovascular diseases, so it should be used as little as possible.