One of Zhang Wuben's shocking theories is that "the thickening agent in yogurt will block blood vessels." With the fall of Master Zhang, this "theory" was treated as nonsense. However, the master's "theory" will still cause some confusion: how is the consistency of yogurt produced? Hot fried "old yogurt", which is said to have added food glue, is it harmful to human body? Does it affect nutrition?

Milk is formed mainly of protein, lactose and fat dispersed in water. Lactose is very soluble in water and has little effect on the appearance of milk. The fat is broken up into small particles that are coated with proteins. In addition to the part that wraps the fat, a lot of the protein stays in the water by itself. Because the surface of protein molecules has some hydrophobic groups, they do not like to be with water molecules, and tend to be close to each other. The proximity of the protein molecules to each other causes them to separate from the water, and the milk is no longer a uniform "liquid" state. Fortunately, there are some charges on the surface of the protein molecules, and the mutual repulsion between the charges resist the mutual attraction caused by the hydrophobic groups, so the protein and the fat particles wrapped in the protein can keep a distance from each other, so as to carry the water safely. On a macro level, what we see is "liquid-like" milk.

Yogurt is the product of milk fermentation by lactic acid bacteria. During fermentation, lactic acid bacteria convert lactose into lactic acid, so the acidity of the milk increases (i.e. the pH level decreases). The charge on the surface of the protein molecule changes with the pH value. For milk proteins, when the pH value drops, the charge will be reduced until there is no charge, the repulsion force generated by the charge will become weaker and weaker, and the tendency of protein molecules to attract each other is stronger and stronger. Eventually, when a large amount of lactose is converted to lactic acid, the pH in the milk is also very low, and the hydrophobic groups between the protein molecules are connected to each other, forming a huge network. This "protein network" contains lactose, water, and fat particles. The macro view is that the milk has become very "sticky" and "sour".

Lactic acid bacteria fermentation makes milk naturally sticky and does not require thickening agents. However, the degree to which the resulting yogurt can stick is mainly related to the solids content of the milk. Usually, the total content of lactose, fat and protein in milk is about 10%, and the yogurt obtained is often not sticky enough. Sometimes it looks solid, but it breaks easily. To get a more viscous semi-solid form of yogurt, you need to increase the solid content. The simplest and most direct way is to add milk powder, which is equivalent to fermentation with a high concentration of milk, and the result is a "pure" "solid yogurt".

The taste of yogurt is closely related to its fat content. However, the fat in milk is mainly saturated fat, but also carries more cholesterol. It is generally believed that the fat in milk helps increase the risk of cardiovascular disease, so people tend to reduce the fat in dairy products or even eat "fat-free dairy products" altogether. Milk with fat removed has a lower solid content, resulting in a yogurt that is more "non-yogurt-like" and tastes worse. In order to solve this problem, people will add some food glue, the most commonly used modified starch, gelatin, pectin and so on. The addition of these ingredients, on the one hand, makes the yogurt "sticky" enough to become the usual semi-solid, on the other hand, it can also simulate the taste of fat to a certain extent.

These food adhesives are commonly referred to as "thickeners." "Thickening" itself only means increasing the viscosity of the liquid, and there are also a large number of "thickening" operations in the chemical industry, so the use of "thickening agents" on food is easy to give people the feeling of "manufacturing fake products". In fact, these food glue itself is a regular food raw material. So-called "thickening" is also common in traditional foods, such as "thickening", which is the use of starch to increase the viscosity of the soup. And jelly, is also a similar carbohydrate form of edible glue.

When such thickeners are eaten in the body, some will be digested into monosaccharic molecules like rice and steamed bread, absorbed by the intestine into the blood circulation, and finally provide energy for human activities, such as starch; Some become amino acids, like gelatin; Some will serve as "dietary fiber," but may provide other health functions. Because they look "sticky", they think they will "block blood vessels", but it is just a "form to complement the form". If thickening agents can block blood vessels, then eating solid food will make blood vessels solid.

Thickening agents are used in yogurt in order to reduce the fat content and obtain proper taste. From a cardiovascular health perspective, this makes a lot of sense. In addition, food gums, such as modified starch and pectin, can provide a sense of satiety but do not provide or provide only a relatively small number of calories, and even help to control weight. In particular, "dietary fiber" such as pectin is a common ingredient that should be increased in modern diets.

However, if the same amount of solid content is compared, in these so-called "old yogurt" with food glue, the "nutrients" from milk - such as protein and calcium - are indeed not as high as regular yogurt. If the goal of eating yogurt is to "nutrient content" in milk, then such "old yogurt" is not as good as ordinary yogurt. The so-called "radish cabbage, each has his own love", everyone has different recipes outside of yogurt, and what he expects to get from eating yogurt is not the same. Again: Know what it offers, know what you want, you choose, you like.