Maarg Manthan · Topic 11.22

Food and Beverage Fermentations: Microorganisms as Food, Enzymes in Food Processing

Science & Technology › Biotechnology – Applications · Topic 11.22

Food and beverage fermentation is the use of microbes such as bacteria, yeasts and moulds to change raw foods into products with new flavour, texture, nutrition and keeping quality. Fermented foods include curd and cheese made with lactic acid bacteria, idli and dosa batter fermented by Leuconostoc and yeast, bread raised by Saccharomyces cerevisiae, vinegar made by Acetobacter, soy sauce and miso made with the mould Aspergillus oryzae, and drinks such as beer, wine and toddy. Microorganisms are also eaten as food, for example mushrooms, yeast extract and the fungal protein in Quorn, and enzymes from microbes are used widely in food processing. Fermentation preserves food because acid and alcohol stop spoilage microbes.

5 min read · UPSC Prelims · Science & Technology · Biotechnology – Applications

At a Glance

Curd and cheese Lactic acid bacteria
Bread and beer Saccharomyces cerevisiae
Vinegar Acetobacter
Soy sauce Aspergillus oryzae
Benefit Flavour, nutrition, preservation
Exam link UPSC Prelims, Science & Technology: Biotechnology – Applications

Where Does It Fit?

This topic follows genetically modified insects. It goes back to the oldest biotechnology, the fermentation of food, and links the microbes and enzymes studied in earlier topics with daily diet. Previous topic: Genetically Modified Insects. Next topic: Amino Acids, Vitamins and Sweeteners from Biotechnology.

Which Microbes Make Which Foods and Drinks?

Food or drink	Microbe and process
Curd and yogurt	Lactobacillus and Streptococcus turn milk sugar into lactic acid, which sets the milk. Curd also gives vitamin B12
Cheese	Milk is clotted with rennet or chymosin and ripened with bacteria and moulds. Swiss cheese holes come from Propionibacterium
Idli and dosa	A batter of rice and black gram ferments with Leuconostoc mesenteroides and yeasts, which raise the batter with carbon dioxide
Bread	Baker’s yeast ferments sugar to carbon dioxide, which makes dough rise
Beer	Barley is malted, mashed to release sugar, boiled with hops and fermented by yeast
Wine	Grape sugar is fermented by wild or added yeast
Vinegar	Alcohol is oxidised to acetic acid by Acetobacter

How Do Microbes and Enzymes Help Food Processing?

Toddy: sap of palm trees ferments naturally into a mild alcoholic drink
Soy products: Aspergillus oryzae gives soy sauce and miso, and Rhizopus gives tempeh
Sauerkraut and kimchi: vegetables are preserved by lactic acid bacteria in brine
Kinema and axone: traditional fermented soybean foods of the Northeast, using Bacillus species
Probiotics: live microbes, such as Lactobacillus and Bifidobacterium, that give health benefit if taken in enough amounts
Prebiotics: fibres that feed good gut microbes
Starter cultures: pure microbe mixtures that give steady quality in dairy and bakery
Enzymes in processing: amylases, proteases, lactase and pectinases improve baking, brewing, dairy and juice, as in Bioprocessing, Bioreactors and Enzyme Manipulation in the Food Industry

What Else Should You Remember?

Microorganisms as food: mushrooms, yeast extract and mycoprotein are eaten as food, while algae like Spirulina are used as supplements, as in Single-Cell Protein Production and Food Fortification
Preservation: lactic acid, alcohol and acetic acid lower the pH or kill spoilage microbes
Nutrition: fermentation can raise B vitamins, make minerals easier to absorb and reduce anti-nutrients
Louis Pasteur: showed in the 1850s and 1860s that fermentation is carried out by living microbes
Distillation: spirits like whisky, rum and brandy are made by distilling fermented liquids
Alcohol content: beer is about 4 to 6 per cent, wine about 10 to 14 per cent, and spirits about 40 per cent alcohol
Kombucha: a fermented tea made with a culture of yeast and bacteria
FSSAI role: the Food Safety and Standards Authority of India sets standards for fermented foods and probiotics, and regulates claims on labels
Food safety risks: poor control can lead to harmful microbes or toxins, such as toxins from moulds, so hygiene and standard cultures matter
Traditional knowledge: India has a rich range of fermented foods across regions, such as dhokla, appam, jalebi batter and bhatura
Gut health: research on the gut microbiome suggests that diet and fermented foods influence digestion and immunity
Link: industrial scale-up follows ideas in Bioprocess and Fermentation Technology
Salt and time: salt level, temperature and time decide which microbes grow, so recipes control the result
Cheese varieties: soft, hard and blue cheeses differ in microbes, moisture and ageing time, and Roquefort type cheeses use the mould Penicillium roqueforti
Yeast in baking: besides gas, yeast adds flavour compounds, and the dough is baked, which kills the yeast
Alcohol control in India: alcohol is a State subject, so excise laws differ by state, while food safety standards for beverages come from FSSAI

Why Does It Matter for the Exam?

Match microbe with food: curd, idli, vinegar, soy sauce
Concepts: probiotics and prebiotics
Brewing steps: malting, mashing, fermentation
Current affairs link: millet based and probiotic foods
Common errors: saying that all fermentation needs oxygen, or that curd is made by yeast

As an analytical point, fermented foods unite tradition and modern science. Standard cultures, hygiene and honest labelling help small producers to enter larger markets safely.

Why Is This Topic Important?

Microbes Match with foods
Health Probiotics
Processing Enzymes

What Came Next?

The next topic covers amino acids, vitamins and sweeteners made by fermentation. Next topic: Amino Acids, Vitamins and Sweeteners from Biotechnology.

Key People and Terms

Starter culture Selected microbes added to food
Probiotic Live helpful microbe
Prebiotic Food for gut microbes
Malting Sprouting grain for brewing
Wort Sugary liquid in brewing
Brine Salt water

Exam Corner

Points to Remember

Curd: Lactobacillus.
Bread: Saccharomyces cerevisiae.
Vinegar: Acetobacter.
Soy sauce: Aspergillus oryzae.
Swiss cheese holes: Propionibacterium.

Do Not Confuse With

Probiotic and prebiotic Live microbes versus their food
Fermentation and distillation Microbial change versus separation by boiling
Yeast and bacteria Fungus for bread and beer versus bacteria for curd

Memory Hook

Curd by Lactobacillus, bread by yeast, vinegar by Acetobacter, soy by the mould.

Mains Angle

Questions ask to match microbes with foods and about probiotics. These points help.

Value Nutrition and preservation
Industry Enzymes and cultures
Safety Standards

A Question You May Face

An original practice question, not a past paper question.

“Discuss the role of microbes and enzymes in food and beverage fermentation and the importance of safety standards.”

How to Answer

Microbes Foods and drinks.
Benefits Taste, nutrition, shelf life.
Enzymes Processing.
Safety Standards, labels.

GS Relevance

Prelims: organisms and products, probiotics, brewing steps. GS Paper 3: food processing, biotechnology and science and technology.

Frequently Asked Questions

Which microbes are used to make curd and idli?

Curd is made by lactic acid bacteria such as Lactobacillus, which convert milk sugar into lactic acid and set the milk. Idli batter ferments through Leuconostoc mesenteroides and yeasts, which produce acid and carbon dioxide gas that makes the batter rise and gives the soft spongy texture.

How is vinegar made?

Vinegar is made in two steps. First, yeast ferments sugar from fruit juice or grain into alcohol. Then bacteria of the genus Acetobacter oxidise the alcohol to acetic acid in the presence of air. The acetic acid gives vinegar its sour taste and its ability to preserve food.

What are probiotics?

Probiotics are live microorganisms, such as certain Lactobacillus and Bifidobacterium strains, that give a health benefit to the host when taken in adequate amounts. They are found in curd and some fermented foods and supplements. The Food Safety and Standards Authority of India regulates probiotic foods and the claims made about them.

What are the steps of brewing beer?

Beer making begins with malting, in which barley is sprouted and dried. The malt is mashed in hot water to release sugars, the liquid wort is boiled with hops, and yeast is added to ferment the sugar into alcohol and carbon dioxide. The beer is then matured, filtered and packed.

Why does fermentation preserve food?

Fermentation preserves food because the microbes produce lactic acid, acetic acid or alcohol, which lower the pH or are toxic to spoilage and disease causing microbes. The fermenting microbes also use up nutrients, leaving less for harmful ones. This is why pickles, curd, vinegar and wine keep longer than their raw materials.

PYQ Practice — Statement Analysis

1 Acetobacter converts alcohol into acetic acid.

True

The step that makes vinegar.

2 Curd is formed by the action of baker's yeast on milk.

False

It is formed by lactic acid bacteria.

3 Aspergillus oryzae is used in making soy sauce.