Lactic Acid Bacteria
லாக்டிக் அமில பாக்டீரியா
Do not mistake curdling for a simple chemical change. It is a controlled biological fermentation process driven by Lactic Acid Bacteria. If you think this is just cooking, you will lose marks on the mechanism of protein coagulation.
The idea
Lactic Acid Bacteria (LAB) act as the inoculum for curd formation. They produce acids that coagulate and partially digest milk proteins, specifically casein. Crucially, LAB significantly improve the nutritional quality of curd by increasing its Vitamin B12 content.
Why it matters
LAB exist to ferment lactose into lactic acid, which acts as a natural preservative and improves the digestibility of milk proteins.
NEET lens
NEET focuses on the specific role of LAB in increasing Vitamin B12. Expect questions linking LAB to nutritional enhancement, not just coagulation. Do not confuse LAB with other fermenting microbes like yeast. Memorize: LAB = Curd = Vitamin B12 increase.
Clinical significance
LAB are essential for gut microbiome homeostasis. A deficiency in these probiotic bacteria leads to dysbiosis, often resulting in antibiotic-associated diarrhea or impaired digestion. They act as a natural defense against pathogenic gut colonization.
Introduction
Lactic acid bacteria (LAB), such as Lactobacillus, convert milk into curd. They grow in milk and produce acids that coagulate and partially digest milk proteins.
Core concept
Curd formation: a small amount of curd added to fresh milk as inoculum (starter) contains millions of LAB, which at suitable temperatures multiply and convert milk to curd. Curd also improves nutritional quality by increasing vitamin B12. In our stomach too, LAB play very beneficial roles in checking disease-causing microbes. Other household products: dough for dosa and idli is fermented by bacteria (the puffed-up appearance is due to CO2 production); dough for bread is fermented using baker's yeast (Saccharomyces cerevisiae); toddy, a traditional drink of southern India, is made by fermenting sap from palms; cheese — large holes in Swiss cheese are due to CO2 produced by Propionibacterium sharmanii, and Roquefort cheese is ripened by specific fungi.
Go deeper
Microbes have been used in Indian kitchens for centuries — curd, idli, dosa and toddy all depend on fermentation.
From Class 10
When you add a spoon of curd to warm milk, bacteria in it turn the milk into curd overnight.