Studies on Idli Fermentation: Part I — Some Accompanying Changes in the Batter

An increase in non-protein nitrogen and a decrease in reducing sugars have been
observed during fermentation of Idli (a popular breakfast dish in South India) batters; the
batters are usually prepared by soaking rice (Oryza sativum) and decuticled black gram
(Phaseolus mungo) dhal in water, grinding them separately, mixing, and allowing the
mixture to ferment overnight. Both titrat-able acidity and the volume of the batter increase
as a result of fermentation and have been used as criteria for judging the progress of
fermentation. A temperature range of 25-30ºC. has been found to be optimal for the
fermentation. Temperatures up to 40°C. accelerated the rate, but some undesirable smell
occasionally developed at higher temperatures.)
Presoaking of black gram dhal prior to grinding in the traditional methods has been
established to be an important step in the fermentation. The possibilities of a ' Flour
Presoaking Method' and a ' Composite Dry Mix Method' for Idli making to eliminate the
need for wet grinding of black gram dhal and rice are indicated by the data.
That both yeasts and bacteria participate in the fermentation has been shown using
penicillin G and chlortetracyclin as selective inhibitors. Acid and gas production have
been found to be mostly dependent on the growth of microbes belonging to the bacterial
group.