Soy yogurt is made by fermenting soymilk with friendly bacteria, mainly Lactobacillus bulgaricus and Streptococcus thermophilus. The process is similar to the production of yogurt from cow milk. Yogurt production was invented probably by accident by Balkan tribes thousands of years ago. Yogurt remained mainly a food of Eastern Europe until the 1900s, when the biologist Mechnikov theorized that lactobacillus bacteria in yogurt are responsible for the unusually long lifespan of the Bulgar people. Mechnikov then popularized yogurt as a foodstuff throughout Europe.
The sugars are fermented by the bacteria into lactic acid, which causes the formation of the characteristic curd. The acid lowers to pH of the yogurt to about 4.0 and restricts the growth of food poisoning bacteria. The bacteria produce lactase which breaks down the lactose in dairy milk. Soy milk does not contain lactose but other sugars such as stachyose and raffinose.
Some countries only allow to use the name "yogurt" for products which have not been pasteurized to kill the bacteria after fermentation. This "live" yogurt is believed to be nutritional superior. The living bacteria are supposed to improve our immune system and the enzymes help to digest food. Sometimes, special probiotic bacteria, which are supposed to improve our gut health, are added to dairy or soy yogurt. These probiotic bacteria, often called good bacteria, are special strains of lactic acid bacteria or Bifidobacterium. A probiotic yogurt contains additional ingredients, such as inuline, that promote the growth of the probiotic bacteria. Soy yogurt always contains natural probiotics: the two soy sugars, stachyose and raffinose, act as probiotics and stimulate the growth of Bifidobacterium in the large intestine. Foods that contains both probiotic bacteria and prebiotic ingredients are called symbiotics.
It is difficult to find soy yogurt in supermarkets but you may find it health food shop. Or you can make soy yogurt at home. You can use store-bought yogurt as starter or even Solgar capsules that contain Lactobacillus bulgaricus and Streptococcus thermophilus. In some countries, soy yogurt is labelled as "cultured soy milk" because the term "yogurt" is reserved for dairy yogurt.
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