Idli Batter Fermentation

Idli batter fermentation is the South Asian technique of naturally leavening a rice and black gram batter used to steam idli cakes. Four parts uncooked rice are combined with one part whole white lentil, or black gram, each soaked separately for at least four to six hours, then the lentils are ground into a fine paste and the rice is ground more coarsely before the two are combined. The mixture is left to ferment overnight, during which it more than doubles in volume. The fermentation is carried out by lactic acid bacteria, particularly the strains Leuconostoc mesenteroides and Enterococcus faecalis, delivered into the batter mainly by the black gram itself, and it both leavens the batter with carbon dioxide and raises its acidity.