Microbes in Household Products

Microbes (bacteria, fungi and others) are not only disease-causing agents - many are extremely useful to us in daily life, especially in the making of food and drink.

Curd

Lactic Acid Bacteria (LAB), such as Lactobacillus, convert milk into curd. They grow in milk and produce acids that coagulate and partially digest the milk proteins. LAB also improve the nutritional quality of the curd by increasing vitamin B12, and in our stomach they help check disease-causing microbes.

Bread and dough

The dough used to make bread is fermented by baker's yeast (Saccharomyces cerevisiae). The yeast releases carbon dioxide, which makes the dough rise (puff up). The same idea is used in making the batter for dosa and idli, which is fermented mainly by bacteria.

Cheese

Cheese is one of the oldest microbial foods; different kinds differ in texture, flavour and taste:

  • Swiss cheese has large holes caused by the production of a large amount of carbon dioxide by the bacterium Propionibacterium sharmanii.
  • Roquefort cheese is ripened by growing a specific fungus, Penicillium roqueforti, on it, which gives it a particular flavour.

Microbes and the household and fermented products they make: curd, cheese, bread, beverages

Toddy

Toddy is a traditional drink of southern India made by fermenting the sap of palms.

One-liners: curd = LAB / Lactobacillus (raises vitamin B12); bread/dough = Saccharomyces cerevisiae (CO2 leavens it); Swiss cheese holes = CO2 by Propionibacterium sharmanii; Roquefort = ripened by Penicillium roqueforti; toddy = fermented palm sap.

Microbes in Fermented Beverages

Microbes, especially the yeast Saccharomyces cerevisiae (also called brewer's yeast), have been used for thousands of years to make alcoholic beverages. The yeast ferments the sugars of malted cereals (barley, wheat) or fruit juices, producing ethanol.

Distilled vs non-distilled

  • Without distillation: wine and beer are produced by fermentation alone, so they have a lower alcohol content. They are non-distilled beverages.
  • With distillation: whisky, brandy and rum are produced by distilling the fermented broth, which raises the alcohol content. They are distilled beverages.

One-liners: brewer's/baker's yeast = Saccharomyces cerevisiae; fermentation gives ethanol; wine and beer = NOT distilled; whisky, brandy, rum = distilled.