Q.Many microbes are used at home during preparation of food items. Comment on such useful ones with examples.
Microbes are used at home to make curd, yoghurt, cheese, buttermilk, fermented batters like dosa/idli/dhokla, and to leaven bread — each relying on a specific bacterium, yeast or mould.
Step 1. Dairy products. Lactic acid bacteria (LAB) such as Lactobacillus are added to milk as a starter; they ferment lactose into lactic acid, which coagulates and partially digests the milk protein casein. Indian curd specifically uses Lactobacillus acidophilus (which also checks disease-causing microbes); yoghurt uses Streptococcus thermophilus together with Lactobacillus bulgaricus; butter milk is the acidulated liquid left after churning butter from curd.
Step 2. Cheese. Milk is coagulated with LAB, the curd is filtered to separate off the whey, and the remaining solid mass is ripened by a specific mould that develops its characteristic flavour — Penicillium roquefortii and P. camembertii ripen Roquefort and Camembert cheese respectively, while the large holes in Swiss cheese come from carbon dioxide produced by Propionibacterium shermanii.
Step 3. Fermented cereal-pulse batters. Dosa, idli and dhokla are all made by fermenting a rice-and-black-gram batter using airborne Leuconostoc and Streptococcus bacteria, whose carbon dioxide output is what puffs the batter up before cooking.
Step 4. Bread. Enzymes and fermenting yeast are similarly used in bread-making, another everyday food product of microbial fermentation.
Everyday microbial foods include curd (Lactobacillus acidophilus), yoghurt (Streptococcus thermophilus + Lactobacillus bulgaricus), cheese (LAB plus ripening moulds), buttermilk (from churned curd), and dosa/idli/dhokla (Leuconostoc and Streptococcus bacteria).
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