• For plant-based (soya, almond, cashew, etc.) unsweetened yogurt, how does the yogurt bacteria grow and develop without sugar?

From online recipes for soya yogurt, one tablespoon of sugar per 1 liter of unsweetened soy milk is needed to promote bacterial fermentation. As these plant-based milk alternatives themselves do not contain sugar (lactose/ milk sugar), for which is the basic food for yogurt bacteria (eg. Lactobacillus delbrueckii subsp. bulgaricus/ Streptococcus salivarius subsp. thermophilus/ bifidobacteria).

  • Also, there is not much sourness in some brands of soya yogurt (eg. Sojade etc). I wonder instead of sugar, what is added to cover the lactic acid that was produced by the yogurt bacteria during fermentation?

Would like to try making unsweetened soya yogurt at home. Appreciate any insights :)

  • The simple answer is you don't. Without sugar there's nothing to feed the bacteria. – GdD Dec 9 '20 at 8:15
  • Lactose is a type of sugar. – Neil Meyer Dec 9 '20 at 17:03

Actually, the yogurt cultures, usually some strain of the group N Streptococcus and Leuconostoc species, mesophilic cultures, converts the lactose into lactic acid, which gives the diary product it's tart taste.

Furthermore, bacterial enzymes transform the milk carbohydrates into oligosaccharides, some of which have prebiotic properties.

Different LAB (Lactic Acid Bacteria) produce different fermentation products, although they have in common that they are alive in the product and can interact with microbiota during intestinal transit and the cells of the intestinal wall.

Fermentation of soy milk with lactic acid bacteria offers a means of preserving soy milk and the possibility of modifying the characteristic flavor and texture to make it more acceptable to Western taste.

It is possible to make soy milk yogurt-like products with acceptable texture and clean acid flavor. The choice of fermenting organisms is limited to those that can ferment the sugars typical of soy milk. i.e. stachyose. raffinose or sucrose. unless sugars fermented by the desired cultures are added to the soy milk.




You are making a wrong assumption here - the soy milk does contain sugars, along with other forms of carbohydrates. So this apparently can be used to make soy yogurt. Thus you have both commercial products and homemade recipes for unsweetened soy yogurt. You can easily find them, I suspect you didn't use the term "unsweetened" when you searched.

If you want to know whether a food contains sugar, you can always look it up in nutrition databases, for example this is an entry for unsweetened soymilk: https://nutritiondata.self.com/facts/legumes-and-legume-products/10341/2

As you see, it has 1 g of sugar per 100 g.

  • 2
    I think the problem arise from the fact that in USA Nutrition label can report that 1g per 100g as zero (because they report values for 100 ml) and "unsweetened" mean "no sugar added after the process of making the yogurt". – SZCZERZO KŁY Dec 9 '20 at 14:39
  • I see, so there are still natural sugars in unsweetened soya milk... Yeh the labels are an issue. Also as they are unsweetened, as I customer, if I see the unsweetened ones are not of 0 g, then I would wonder, so this make sense! – Ryan Dec 9 '20 at 17:50

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