Science Behind Idli Fermentation


Idli is healthy food that is made of rice or sooji batter through a process called Fermentation.

Fermentation is a science that happens with the rapid growth of micro-organisms.

Before going into the details of the science behind Fermentation, let’s take a quick review on how Idli is made. For quicker result, one can also add ENO which is a fruit salt, but slow overnight fermentation is preferred as it is good from nutrients perspective too.

Traditional form of making idlis is as follows:

1. Take desired quantity of rice and urad daal (black gram), and soak them separately in water overnight

2.Drain excess water, grind rice and black gram separately with occasional addition of water during grinding process

3. Two batters are then mixed together with addition of a little salt

4. Keep mixture to ferment overnight at room temperature

5. Fermented batter is dispensed in special idli pans and allowed for steaming for 5–8 min

Science of Fermentation of Idli

Overnight fermentation of idli batter allows the rapid growth of the naturally occurring microorganisms viz. Leuconostoc mesenteroides and Streptoccous thermophilus in grains/legumes/utensils. These microorganisms divide and produce lactic acid and carbon dioxide that make the batter anaerobic and leaven the product. Bubbles of carbon dioxide form a Froth on top of the fermentation mixture.

Changes during fermentation are highly significant for nutritional point of view also:

  • During fermentation, vitamins B (Riboflavin, Thiamine and  folic acid) and Vitamin C increase.
  • Increase in free sugar, non-protein nitrogen, free nicotinic acid, methionine and chlorine
  • Phytate is hydrolyzed almost to 50%
  • An increase in methionine, a limiting essential amino acid in legumes, greatly improves protein value

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