In yogurt, lactic acid bacteria occupy an absolute advantage. At the cold storage temperature (that is, the fresh-keeping temperature of refrigerator), the number of live lactic acid bacteria hardly increases, which has a certain inhibitory effect on other miscellaneous bacteria.
If yogurt is kept at room temperature, this process will be greatly accelerated. At the fresh-keeping temperature, the time scale of this process can be measured by "days", while it needs to be described by "hours" at room temperature.
If the raw materials and hygiene control in the production process are better, the quality of yogurt can be acceptable after two or three weeks of cold storage. At room temperature, I may not be able to eat it after a few hours.
Because the change of flavor and taste occurs before the decrease of live bacteria and the increase of miscellaneous bacteria, the "shelf life" of yogurt is measured by the change of flavor and taste. So whether in the refrigerator or at room temperature, if there is no odor and the appearance and taste are good, you can eat it.
Procurement guide
Faced with all kinds of yogurt products placed in supermarkets, consumers should first look at the marked "product category" when purchasing. If it says "fermented milk", it is yogurt.
If ingredients other than milk, sugar, fermentation strains and thickener are added to yogurt, it is called "flavored fermented milk". For example, most yogurt products added with fruit juice, fruit granules, malt, miscellaneous grains and coconut are flavored fermented milk.
In addition, we should pay attention to the "nutrient composition table" of products when purchasing, and it is best to buy products with high protein, low fat and low carbohydrate.
Please refer to People's Daily Online-What is the shelf life of "yogurt"?
The above contents refer to Baidu Encyclopedia-Flavor Fermentation.