Microbes in Human Welfare Test - 14

Saccharomyces cerevisiae is also known as baker’s yeast. This yeast is used for fermenting wheat flour after it is kneaded. Similarly, the dough which is used for making bread is also fermented using baker’s yeast.

The dough which is used for making foods such as dosa and idli is fermented by using bacteria like Streptococcus. The puffed-up appearance of this dough is due to the production of CO₂ gas.

Baker’s yeast produces 3 enzymes namely-amylase, maltase and zymase. Amylase changes a small amount of starch into maltose. Maltase changes maltose to glucose and zymase acts on glucose to form bubbles of ethyl alcohol and carbon dioxide.

Rice and black gram are soaked overnight, washed, mixed and ground. The mixture is allowed to undergo fermentation with the help of Leuconostoc mesenteroides and Streptococcus faecalis.

Soybean products include Tempeh, Sofu, Tofu and soy sauce. Sofu and Tofu are cheese-like products of soybean obtained after fermentation with Mucor species. While tempeh is an Indonesian food formed by fermenting, drying, salting and frying of soybean.

LAB stands for Lactic acid bacteria. Indian curd is prepared from both skimmed and cream milk by inoculating the milk with lactic acid bacteria.

Yoghurt is fermented milk. The milk is heated to 80-90°C for half an hour and then it is cooled to 40-43°C and mixed with an inoculum containing Streptococcus thermophilus and Lactobacillus bulgaricus. Preparation of yoghurt takes approximately 4-5 hours. The original flavour of yoghurt and other fermented kinds of milk is of acetaldehyde.

Cheese is pressed and flavoured milk curd and more than 2000 varieties of cheese are known. Some of the types include Raw cheese, cottage cheese, Swiss cheese, camembert cheese, Roquefort cheese, etc.

Cottage milk cheese is an unripened soft cheese which is prepared by inoculating skimmed milk first with cheese culture of Streptococcus lactis and then rennin or chymosin which is obtained from a fungus source.

Ripening of cheese is carried out to provide cheese with a characteristic texture, flavour and taste. There are three types of ripened cheese- soft cheese, semi-soft cheese and hard cheese.

Ripening of cheese is carried out with the help of specific microbes. For example, Camembert cheese is ripened with the help of Penicillium camembertii. Roquefort cheese and Swiss cheese are ripened with the help of Penicillium roquefortii and Propionibacterium sharmani respectively.

Sausages are fermented meats which possess particular flavour and its taste depends upon the fermenting agent. The most commonly employed microbe is a lactic acid bacterium. The bacterium also preserves the sausages.

Coconut water is fermented to produce a refreshing drink called toddy. It is a traditional drink in some parts of Southern India. Palm sugar or jaggery is produced by boiling it. Arrack is obtained by the distillation of fermented toddy.

In 1864, Pasteur discovered the process of pasteurisation. It is a process of preservation of milk, wine and other liquids by heating for a short period and then cooling suddenly. This kills most of the microbes.

Live microbial food is called as probiotics, therefore single-cell protein is also referred to as probiotics. It is protein-rich microbial biomass which can be used as food and feed.