Curd, dough and cheese

Curd is made from milk by Lactobacillus and other lactic acid bacteria (LAB). The acids they produce while growing coagulate the milk proteins and partly digest them.

A spoonful of curd added to fresh milk acts as the inoculum or starter: it carries millions of LAB, which multiply at a suitable temperature and turn the milk into curd.

Curd is more nutritious than milk because LAB raise its vitamin B12 content. In our stomach, LAB also help keep disease-causing microbes in check.

The dough for dosa and idli is fermented by bacteria; it puffs up because of the CO₂ gas produced.

Bread dough is fermented with baker's yeast, Saccharomyces cerevisiae.

Toddy, a traditional drink in parts of southern India, comes from palm sap left to ferment. Fish, soyabean and bamboo shoots are likewise fermented by microbes to make foods.

Cheese is among the oldest foods made with microbes; each variety owes its texture, flavour and taste to particular microbes.

The large holes in Swiss cheese come from the large amount of CO₂ produced by the bacterium Propionibacterium sharmanii. Roquefort cheese gets its flavour from a particular fungus grown on it during ripening.