Milk is converted to curd by micro-organisms such as Lactobacillus and others commonly called lactic acid bacteria (LAB) which grow in milk and convert it to curd.
During growth of bacteria, the LAB produce acids that coagulate and partially digest the milk proteins.
A small amount of curd added to the fresh milk as inoculum or starter which at suitable temperatures multiply, thus converting milk to curd, which also improves its nutritional quality by increasing vitamin B12.
In our stomach, the LAB play very beneficial role in checking disease causing microbes.
The dough, which is used for making foods such as dosa and idli is also fermented by bacteria.
The puffed-up appearance of dough is due to the production of CO2
The dough, which is used for making bread, is fermented using baker’s yeast (Saccharomycescerevisiae).
A number of traditional drinks and foods are also made by fermentation by the microbes.
Toddy, a traditional drink of some parts of southern India is made by fermenting sap from palms.
Microbes are also used to ferment fish, soya bean and bamboo shoots to make foods.
3. Production of cheese
Different varieties of cheese are known by their characteristic texture, flavor and taste, the specificity coming from the microbes used.
The large holes in ‘Swiss cheese’ are due to production of a large amount of CO2 by a bacterium named Propionibacterium sharmanii.
The ‘Roquefort cheese’ are ripened by growing a specific fungi on them, which gives them a particular flavor.