Yogurt is a combination of milk, which is often viewed as a complete food containing a good balance of nutrients, and the amazing benefits of lactic acid bacteria. So, yogurt has all the nutrients you can find in milk, some of which have been enhanced and become more potent.
Yogurt is made by mixing milk with a starter culture.
The typical starter culture contains Lactobacillus delbrueckii subsp. bulgaricus, which is a type of bacillus, and Streptococcus thermophilus, which is a type of coccus. In addition, other species of lactic acid bacteria are added depending on the type of yogurt being made, which include Lactobacillus gasseri, Lactobacillus acidophilus, bifidobacteria, etc.
The lactic acid produced by those lactic acid bacteria adds a sour yet soothing flavor to the yogurt. Also, as lactic acid causes milk proteins to curdle like tofu, it creates a uniquely smooth texture.
These two species of lactic acid bacteria are the main active bacteria that produce yogurt through a natural process. These particular bacteria have been used to make yogurt since ancient times, as they are able to proliferate faster together than when used separately.
Indeed, when L. bulgaricus and S. thermophilus are mixed into milk together, S. thermophilus, which is the faster grower of the two, increases in number quickly by feeding off small amounts of amino acids and peptides found in the milk, while producing the formic acid that L. bulgaricus needs to proliferate.
Then, L. bulgaricus takes up this formic acid and grows its population while producing amino acids and peptides that promote the growth of S. thermophilus.
In other words, these two lactic acid bacteria used to make Bulgarian-style yogurt compensate for each other’s weakness to proliferate and produce large amounts of lactic acid in the process.
yogurt is made relatively quickly through the symbiotic collaboration between these two strains of bacteria that facilitate the lactic acid fermentation process.