Fermentation gives yogurt its "magic", but probiotics may not have the "magic"

In daily life, yogurt is a favorite of many people. Compared with milk, yogurt has a unique taste and has attracted a large number of customers. In order to cater to consumers' preferences, there are also a wide variety of yogurt products on the market, including old yogurt, fruit-flavored yogurt, etc. Yogurt, also known as sour milk, is a food made from milk as the main raw material and fermented by lactic acid bacteria. However, even though people often drink yogurt, few people really "understand yogurt".

Fermentation gives yogurt its magic

Yogurt is fermented from milk, and this process is inseparable from lactic acid bacteria . Lactic acid bacteria is a kind of anaerobic bacteria widely distributed in nature. Its magic lies in that it can produce a large amount of lactic acid by fermenting glucose or other sugars. There are many members of the lactic acid bacteria family, the most common ones are lactobacillus, lactic streptococcus, bifidobacterium, etc. The transformation of milk into yogurt is that under anaerobic conditions , the original natural lactic acid bacteria in the milk or the artificially added lactic acid bacteria can decompose the lactose in the milk to produce a large amount of lactic acid , causing the pH value of the milk to drop and the milk to become sour . The acidic conditions can cause the casein in the milk to coagulate and precipitate, so that the milk begins to thicken. In this way, the "sour" and "thick" characteristics of yogurt are both revealed.

Yogurt rumor-busting moment

When choosing yogurt, many people tend to choose low-temperature yogurt, believing that it has higher nutritional value. In fact, low-temperature yogurt and room-temperature yogurt are both products of milk fermentation. The nutrients such as protein, calcium, and vitamins contained in the two are almost the same. The biggest difference is whether there are live lactic acid bacteria. Some people also think that the nutritional value of yogurt is positively correlated with sourness. The sourer the yogurt, the higher the nutritional value. This is also wrong. The acidity of yogurt has no direct relationship with its nutritional value. The main reasons that affect the acidity of yogurt are the acid-producing ability of the strain , the length of fermentation time , the storage method , and the amount of sugar added .

Does yogurt have these advantages ? Not necessarily

In daily conversations, the idea that yogurt helps digestion is very popular. Some people even list drinking yogurt as a way to solve constipation. On the question of whether yogurt really helps digestion, some experts have given the following explanation. Yogurt is only friendly to the human intestines and can reduce the chance of gastrointestinal infections, but there is currently no evidence that yogurt can promote digestion . In fact, eating yogurt after eating a lot of food does not make the food digest quickly, but instead increases calories.

Does yogurt have these disadvantages ? Not necessarily

Some people think that the calcium content of fermented yogurt is definitely not as good as that of milk. In this regard, yogurt wants to protest that its calcium supplement effect is not inferior to that of milk . The fermentation process does not reduce the calcium content in milk, but increases it. Some people compare the nutritional content of yogurt and milk. 100 grams of yogurt can provide 118 mg of calcium, while the calcium content of the same amount of milk is 104 mg. In addition, the lactose, protein and fat in yogurt are partially decomposed, making it easier for the human body to digest and absorb. The lactic acid produced by fermentation can promote calcium absorption.

"Everyone should drink less yogurt, because thickeners are added to yogurt, which will thicken the blood." This message, which was once widely circulated in the circle of friends, really made yogurt take the blame. When making yogurt, there will be some thickeners, such as pectin, agar, edible gelatin, etc. They are all large molecular substances. Most of them will not be digested and absorbed after entering the human body. The effect is similar to that of dietary fiber and will not change the blood viscosity of the human body.

Are the probiotics in yogurt really useful ?

In daily life, when consumers buy yogurt, they often see slogans such as "millions of probiotics" and "live probiotics", but some test results are not always true. The Technical Center of the Zhuhai Entry-Exit Inspection and Quarantine Bureau of Guangdong Province once tested the total number of lactic acid bacteria, protein and calcium content of different yogurts. The results showed that most low-temperature yogurts contained very few lactic acid bacteria after simulated digestion tests, and the sugar content of room-temperature yogurt was generally high, and some yogurts even had almost no lactic acid bacteria detected .

Moreover, the nutrition community has not yet reached a consensus on whether the intake of probiotics can regulate the intestines . An expert said: "The intestines can be described as a 'sea of ​​bacteria'. If the number of beneficial bacteria entering the human intestine is small, it basically has no effect." Therefore, some yogurt products advertise that their probiotics are added in amounts of tens of billions, and advocate the efficacy of these live bacteria, but there is actually no basis for this. There are hundreds of billions of bacteria in each milliliter of coliform bacteria, and the total weight of bacteria in the intestines is about 1.5 kilograms. Even if all of them reach the intestines, a few hundred million probiotics are really insignificant compared to them.

Of course, as a product with a special taste and high nutritional value, yogurt is still very suitable for daily drinking. However, remember to choose "real" yogurt when purchasing. There are many manufacturers on the market that confuse yogurt with milk drinks. From the national standard definition and nutritional content standards, yogurt refers to a product made from raw cow (sheep) milk or milk powder, sterilized, inoculated with thermophilic streptococci and bulgaricus, and fermented. The protein content of the product shall not be less than 2.9g/100g. Even flavored yogurt with other raw materials added should contain more than 80% raw cow (sheep) milk or milk powder, and the protein content shall not be less than 2.3g/100g. However, milk drinks and milk beverages refer to beverage products made from milk or dairy products as raw materials, added with water and appropriate auxiliary materials, and prepared or fermented. Compared with yogurt, milk drinks have a lower protein content. In relevant regulations, the protein content of prepared milk-containing beverages and fermented milk-containing beverages shall not be less than 1g/100g, and the protein content of lactic acid bacteria beverages shall not be less than 0.7g/100g. The protein content of real yogurt and fake yogurt is quite different.

Author: Cheng Fangjie

Scientific review: Wu Xinsheng, deputy chief physician, Department of Gastroenterology, PLA 371 Hospital