The essentials
Many foods made in Indian homes depend on microbes. When a small amount of curd is added to milk as a starter (inoculum), lactic acid bacteria (LAB) such as Lactobacillus multiply. They produce lactic acid, which coagulates and partially digests milk proteins, turning milk into curd. LAB also raise the vitamin B₁₂ content of curd, and in the stomach they help check the growth of disease-causing microbes.
Dough for dosa and idli is fermented by bacteria; the puffed-up look comes from carbon dioxide gas released during fermentation. Bread dough is leavened by baker's yeast, Saccharomyces cerevisiae, which ferments sugars and releases CO₂ that makes the dough rise. Toddy, a traditional drink of parts of southern India, is made by fermenting sap from palms.
Microbes are also used to ferment fish, soybean and bamboo shoots, and to make cheese. Different cheeses get their texture, flavour and taste from particular microbes. The large holes in Swiss cheese are due to a large amount of CO₂ produced by the bacterium Propionibacterium sharmanii. Roquefort cheese is ripened by growing specific fungi on it.
Key points
- Curd: Lactobacillus and other LAB; lactic acid; vitamin B₁₂ increases.
- Bread: Saccharomyces cerevisiae (baker's yeast); CO₂ makes dough rise.
- Idli and dosa batter: bacterial fermentation produces CO₂.
- Swiss cheese: Propionibacterium sharmanii.
- Roquefort cheese: ripened by fungi.
Common mistakes
- LAB increase vitamin B₁₂, not vitamin C or vitamin K.
- Yeast is a fungus, not a bacterium; Lactobacillus is a bacterium.
- The holes in Swiss cheese come from gas, not from fungal growth.