Microorganisms and Our Food

Microorganisms are tiny organisms that are too small to see clearly without a microscope.

They include:

• bacteria
• yeasts
• molds
• other microscopic fungi

We often associate microorganisms with disease or food spoilage, but many microorganisms are:

useful.

Humans have used microorganisms to produce and preserve food for thousands of years.

Microorganisms help make foods such as:

• bread
• yogurt
• cheese
• sauerkraut
• kimchi
• soy sauce
• vinegar
• fermented beverages

The controlled use of microorganisms to make useful products is an important example of:

biotechnology.

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What Is Food Biotechnology?

Food biotechnology involves using organisms, cells, enzymes, or biological processes to produce or modify food.

One of the oldest forms of food biotechnology is:

fermentation.

During fermentation, microorganisms use nutrients in food and convert them into new substances.

These substances can change the food's:

• taste
• texture
• smell
• nutritional characteristics
• storage life

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Microorganisms as Tiny Food Factories

Microorganisms obtain nutrients from their surroundings.

As they metabolize these nutrients, they produce different:

products.

For example:

yeast + sugar → ethanol + carbon dioxide

and

lactic acid bacteria + sugar → lactic acid

Humans can use these microbial products to create foods with desirable properties.

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Fermentation in Food Production

Fermentation is one of the most important microbial processes used in food production.

During fermentation, microorganisms convert substances such as sugars into other compounds.

Common products include:

• lactic acid
• ethanol
• carbon dioxide
• acetic acid
• flavor compounds

The products depend on the microorganism and conditions being used.

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Yeast in Food Production

Yeast is a type of single-celled fungus.

One of the most important species used in food production is:

Saccharomyces cerevisiae.

Yeast can break down sugars through alcoholic fermentation.

A simplified word equation is:

glucose → ethanol + carbon dioxide + energy

Both carbon dioxide and ethanol have useful applications in food production.

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Bread Production

Bread is one of the most familiar examples of food biotechnology.

The main microorganism involved is:

yeast.

Yeast is mixed into dough containing carbohydrates.

Enzymes help make sugars available, and the yeast uses these sugars as an energy source.

During fermentation, yeast produces:

carbon dioxide.

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Why Does Bread Rise?

Carbon dioxide produced by yeast forms:

gas bubbles.

The dough contains proteins, including gluten, that help trap these bubbles.

As more carbon dioxide accumulates:

the dough expands and rises.

During baking, the bread structure becomes fixed.

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What Happens to the Ethanol in Bread?

Yeast also produces:

ethanol.

During baking, much of the ethanol evaporates because of the high temperature.

The important fermentation product for making bread rise is:

carbon dioxide.

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Conditions for Yeast Growth

Yeast activity depends on environmental conditions.

Important factors include:

• temperature
• moisture
• sugar availability
• pH
• oxygen availability

Warm conditions generally increase yeast activity up to an optimum.

Very high temperatures can:

kill the yeast.

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Why Does Dough Rise Slowly in a Refrigerator?

Low temperatures reduce the rate of:

enzyme-controlled reactions.

Yeast therefore metabolizes sugars more slowly.

Less carbon dioxide is produced per unit time.

The dough consequently:

rises more slowly.

This does not necessarily mean fermentation has completely stopped.

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Yogurt Production

Yogurt is made using:

lactic acid bacteria.

Common bacterial groups used in yogurt production include Lactobacillus and Streptococcus species.

These bacteria ferment sugars found in:

milk.

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How Is Yogurt Made?

A simplified process is:

milk → beneficial bacteria added → bacteria ferment lactose → lactic acid produced → pH decreases → milk proteins change → yogurt forms

The bacteria convert milk sugar into:

lactic acid.

This gives yogurt its characteristic acidic taste.

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Why Does Yogurt Become Thick?

As bacteria produce lactic acid:

pH decreases.

The increasing acidity changes the structure and interactions of milk proteins.

The proteins form a network that traps water.

This gives yogurt its:

thicker texture.

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Starter Cultures

A starter culture is a selected population of microorganisms added to food to begin a controlled fermentation.

Starter cultures are useful because manufacturers can select microorganisms that produce desirable:

• flavors
• textures
• acids
• aromas
• fermentation rates

Using known cultures also makes production more:

predictable.

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Cheese Production

Microorganisms are essential in the production of many:

cheeses.

Lactic acid bacteria convert milk sugars into:

lactic acid.

This helps acidify the milk and contributes to the formation of curds.

Different microorganisms can then contribute to:

• flavor
• smell
• texture
• appearance
• ripening

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Cheese Ripening

Many cheeses develop their characteristic properties during:

ripening or aging.

Microorganisms and their enzymes break down components of the cheese.

These chemical changes can produce:

• new flavor molecules
• changes in texture
• characteristic aromas

Different microbial communities help produce different types of cheese.

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Molds in Cheese Production

Some cheeses deliberately use:

molds.

Species of Penicillium are used in several cheeses.

For example, particular molds contribute to the characteristics of:

• blue cheeses
• Brie
• Camembert

The mold is not accidental contamination.

It is deliberately selected and controlled as part of:

food production.

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Not All Molds Are Safe

The fact that some molds are used in food production does not mean that:

all moldy food is safe to eat.

Different molds produce different substances.

Some can produce harmful:

mycotoxins.

Food microorganisms must therefore be carefully selected and controlled.

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Fermented Vegetables

Microorganisms are used to produce fermented vegetables such as:

• sauerkraut
• kimchi
• some traditional pickles

Lactic acid bacteria use sugars naturally present in the vegetables.

They produce:

lactic acid.

This changes the flavor while also helping preserve the food.

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Sauerkraut

Sauerkraut is produced by fermenting:

cabbage.

Salt helps create conditions that favor useful fermentation microorganisms.

Lactic acid bacteria then convert sugars in the cabbage into:

lactic acid.

As acidity increases, conditions become less suitable for many spoilage microorganisms.

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Kimchi

Kimchi is another example of vegetable fermentation.

Vegetables are combined with ingredients such as:

• salt
• seasonings
• spices

Microbial fermentation produces acids and many flavor compounds.

The result is a food with distinctive:

taste, aroma, and texture.

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Soy Sauce

Soy sauce is produced through a complex fermentation process involving microorganisms.

Depending on the production method, these can include:

• molds
• yeasts
• bacteria

The microorganisms and their enzymes break down:

proteins and carbohydrates.

This produces amino acids, sugars, acids, and aroma compounds that contribute to the characteristic flavor of soy sauce.

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Vinegar

Vinegar production involves microorganisms converting ethanol into:

acetic acid.

Acetic acid bacteria, including species of Acetobacter, can perform this process when oxygen is available.

A simplified sequence is:

sugars → ethanol → acetic acid

Acetic acid gives vinegar its characteristic:

sour taste.

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Microorganisms and Food Preservation

Microorganisms may seem like a strange way to preserve food.

After all, microorganisms can cause food to:

spoil.

However, controlled fermentation uses selected microorganisms to create conditions that make it harder for many unwanted microorganisms to grow.

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Acid as a Preservative

Lactic acid bacteria produce:

lactic acid.

As lactic acid accumulates:

pH decreases.

Many spoilage organisms and pathogens grow poorly under sufficiently acidic conditions.

Therefore:

fermentation → acid production → lower pH → reduced growth of some unwanted microorganisms

This can extend the food's storage life.

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Ethanol as a Preservative

Ethanol produced during alcoholic fermentation can also inhibit the growth of some microorganisms.

At sufficient concentrations, ethanol interferes with:

cell membranes and proteins.

This contributes to the preservation of some fermented products.

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Salt and Fermentation

Salt is often used when fermenting vegetables.

Salt can:

• draw water from plant tissues
• influence which microorganisms grow
• inhibit some unwanted microorganisms
• favor useful salt-tolerant fermenters

The correct concentration is important.

Too little salt may allow undesirable microorganisms to grow.

Too much may inhibit the desired:

fermentation.

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Multiple Preservation Factors

Fermented foods are often protected by several factors simultaneously.

For example:

salt + low pH + microbial competition + refrigeration

may work together.

This is more effective than relying on a single:

preservation method.

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Microbial Competition

Useful microorganisms can reproduce and use available nutrients.

This leaves fewer resources for:

unwanted microorganisms.

Some useful microorganisms also produce compounds that inhibit competitors.

Therefore, selected microbes can sometimes help control the microbial community within a food.

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Beneficial Microorganisms

A beneficial microorganism is a microbe whose activity provides a useful effect.

In food production, beneficial microorganisms may:

• produce acids
• produce carbon dioxide
• create flavors
• modify texture
• preserve food
• produce enzymes
• improve manufacturing processes

However, whether a microorganism is beneficial depends on:

the situation.

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Useful Microbe or Spoilage Organism?

Consider yeast.

In bread dough:

useful

because it produces carbon dioxide.

In a product where yeast growth is unwanted:

spoilage organism.

Therefore, microorganisms are not simply:

good or bad.

Their effects depend on the species, food, and conditions.

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Probiotics

Some foods contain live microorganisms described as:

probiotics.

A probiotic is a live microorganism that, when administered in adequate amounts, provides a demonstrated health benefit to the host.

Some fermented foods may contain live microbes, but:

not every fermented food is automatically probiotic.

A probiotic claim requires evidence for a specific microorganism and benefit.

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Food Safety

Using microorganisms in food production requires:

careful control.

If harmful microorganisms contaminate food, they may cause:

• food spoilage
• toxin production
• foodborne disease

Food biotechnology therefore depends on both:

microbiology and food safety.

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Foodborne Pathogens

Microorganisms capable of causing disease through contaminated food include some strains or species of:

• Salmonella
• Escherichia coli
• Listeria
• Campylobacter

Food producers must prevent these organisms from reaching dangerous levels.

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Contamination

Contamination occurs when unwanted microorganisms or other harmful substances enter food.

Contamination can occur through:

• raw ingredients
• workers
• equipment
• water
• air
• pests
• storage containers
• cross-contamination

Good manufacturing practices reduce these risks.

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Temperature Control

Temperature is extremely important in microbial food production.

Microorganisms have:

optimum temperature ranges.

During fermentation, producers may maintain a temperature that favors the desired microorganism.

After production, refrigeration may be used to:

slow microbial growth.

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Why Refrigeration Works

Low temperatures slow many:

enzyme-controlled reactions.

As a result, many microorganisms:

• reproduce more slowly
• metabolize food more slowly
• produce substances more slowly

Refrigeration therefore slows spoilage but does not necessarily:

kill microorganisms.

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Pasteurization

Pasteurization uses controlled heating to reduce the number of harmful and spoilage microorganisms in foods and beverages.

It is commonly associated with products such as:

milk.

Pasteurization improves safety while trying to maintain the desirable properties of the food.

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Pasteurization Is Not Sterilization

Pasteurization does not necessarily eliminate:

all microorganisms.

Its purpose is to reduce important pathogens and spoilage organisms to safer levels.

Sterilization, in contrast, is designed to eliminate all viable microorganisms or microbial life to a defined standard.

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Hygiene in Food Production

Good hygiene is essential when using microorganisms commercially.

Workers may need to:

• wash hands
• sanitize equipment
• protect ingredients from contamination
• control pests
• maintain clean surfaces
• monitor storage temperatures

The goal is to allow:

desired microorganisms

while preventing:

unwanted microorganisms.

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Industrial Food Fermentation

Large-scale food production often uses:

fermenters or bioreactors.

These allow manufacturers to control conditions such as:

• temperature
• pH
• oxygen
• mixing
• nutrients
• fermentation time

Controlled conditions help produce food that is:

consistent and safe.

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Quality Control

Food manufacturers test products to ensure they meet appropriate standards.

Quality control may involve monitoring:

• pH
• temperature
• microbial populations
• appearance
• texture
• taste
• chemical composition
• contamination

This helps ensure that each batch is:

consistent.

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Benefits of Microbial Food Production

Microorganisms provide many benefits.

They can:

• preserve food
• create new flavors
• create desirable textures
• produce carbon dioxide
• produce useful acids
• transform raw ingredients
• increase product variety
• support large-scale manufacturing

Fermentation can also reduce food waste by extending the usable life of some foods.

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Benefit: Preservation

Before refrigerators existed, fermentation provided an important way to preserve:

perishable foods.

Acid, ethanol, salt, and competition from useful microorganisms can inhibit unwanted microbial growth.

This allowed food to be stored for:

longer periods.

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Benefit: Flavor

Microorganisms produce many chemical compounds.

These contribute to the flavors of:

• cheese
• yogurt
• soy sauce
• sourdough
• fermented vegetables

Without microbial metabolism, many familiar foods would taste:

completely different.

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Benefit: Texture

Microorganisms can also change food texture.

Examples include:

milk → yogurt

and

dough → risen bread.

These changes result from microbial products interacting with the food's physical and chemical structure.

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Benefit: Nutritional Changes

Fermentation can change the nutritional characteristics of food.

Microorganisms may:

• break down certain carbohydrates
• produce some vitamins
• make some nutrients more accessible
• reduce concentrations of certain undesirable compounds

However, the nutritional effect varies considerably between:

foods and fermentation processes.

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Benefit: Lactose Reduction

During some dairy fermentations, microorganisms use:

lactose.

This can reduce the amount of lactose present compared with the original milk.

Some people therefore tolerate certain fermented dairy products differently from:

unfermented milk.

The amount of lactose varies among products.

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Risks of Microbial Food Production

Microbial food production also has risks.

These include:

• contamination by pathogens
• growth of unwanted microorganisms
• toxin production
• incorrect fermentation conditions
• spoilage
• inconsistent products
• allergic or intolerance-related concerns with particular foods

Careful control is therefore essential.

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Risk: Pathogenic Contamination

If pathogenic microorganisms enter a food-production system, they may reproduce.

If the food is then consumed, the pathogen may cause:

foodborne disease.

This risk can be reduced through:

• hygiene
• temperature control
• safe ingredients
• monitoring
• appropriate processing

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Risk: Toxin Production

Some microorganisms can produce:

toxins.

A food may therefore become unsafe even if the microorganism itself is later reduced.

This is one reason proper food storage is important from the:

beginning.

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Risk: Incorrect Fermentation

If fermentation conditions are poorly controlled:

• desired microbes may grow too slowly
• unwanted microbes may dominate
• pH may not decrease sufficiently
• undesirable products may form

Successful fermentation therefore requires:

appropriate conditions.

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Evaluating Benefits and Risks

A useful evaluation should consider both sides.

Benefits

• preservation
• flavor development
• improved texture
• food variety
• efficient production
• possible nutritional changes

Risks

• contamination
• foodborne disease
• toxin production
• spoilage
• need for careful process control

The benefits of microbial food production depend on using:

appropriate microorganisms under controlled conditions.

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Microorganisms in Everyday Life

Microbial biotechnology is probably already present in your:

kitchen.

A typical meal might contain:

bread

made using yeast,

yogurt

made using bacteria,

cheese

made using bacteria and sometimes fungi,

and:

soy sauce

produced through microbial fermentation.

Food biotechnology is therefore not simply a laboratory technology.

It is part of:

everyday life.

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Sourdough Bread

Sourdough provides a good example of a microbial community.

A sourdough starter usually contains:

yeasts + lactic acid bacteria.

The yeast contributes gases that help the dough rise.

The bacteria produce acids that contribute to:

flavor and acidity.

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Different Microbes Working Together

Food fermentation often involves more than one species.

One microorganism may produce a substance that another can:

use.

Microbial communities can therefore interact.

These interactions help create the complex flavors found in many traditional fermented foods.

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Traditional Food Biotechnology

Humans practiced food biotechnology long before they knew microorganisms existed.

People discovered that certain processes could:

• preserve milk
• make bread rise
• preserve vegetables
• produce new flavors

Knowledge was passed from generation to generation.

Later, microbiology explained:

why these processes worked.

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Louis Pasteur and Fermentation

During the nineteenth century, scientists including Louis Pasteur demonstrated that fermentation was connected to the activity of:

microorganisms.

This helped establish the scientific study of microbiology and transformed understanding of food production and spoilage.

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Modern Food Biotechnology

Modern food biotechnology combines traditional fermentation with:

• microbiology
• genetics
• biochemistry
• engineering
• quality control

Scientists can select microbial strains with desirable characteristics.

In some applications, microorganisms can also be genetically modified to produce useful:

enzymes or ingredients.

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Microbial Enzymes in Food Production

Microorganisms can produce enzymes used by the food industry.

Examples include enzymes that help:

• break down starch
• process proteins
• modify fats
• produce sugars
• clarify beverages
• manufacture cheese

The microorganism may produce the enzyme in an industrial fermenter.

The enzyme is then:

collected and purified.

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Food Waste and Biotechnology

Microbial processes may also help reduce:

food waste.

For example, microorganisms can convert some agricultural materials into:

• food ingredients
• animal feed
• useful chemicals
• fermentation products

This can increase the usefulness of biological resources.

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Worked Example 1

A baker adds yeast to bread dough.

What does the yeast produce that causes the dough to rise?

Carbon dioxide.

The gas becomes trapped in the dough.

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Worked Example 2

Bacteria are added to milk and the pH decreases.

What is likely being produced?

Lactic acid.

The bacteria are fermenting milk sugars.

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Worked Example 3

Cabbage is mixed with salt and allowed to ferment.

Why can this help preserve the cabbage?

Lactic acid bacteria produce:

acid.

The lower pH inhibits the growth of many unwanted microorganisms.

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Worked Example 4

A cheese manufacturer deliberately adds a selected mold.

Is this necessarily contamination?

No.

Some selected molds are intentionally used to create particular cheeses.

The key is that the microorganism is:

known and controlled.

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Worked Example 5

A yogurt factory accidentally becomes contaminated with an unwanted bacterium.

Why is this a concern?

The bacterium could:

• spoil the yogurt
• compete with the starter culture
• alter the product
• potentially cause disease

Contamination control is therefore essential.

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Worked Example 6

A food is placed in a refrigerator.

Does refrigeration sterilize it?

No.

Refrigeration mainly:

slows microbial growth.

Many microorganisms can survive refrigeration.

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Worked Example 7

A student says all fermented foods contain probiotics.

Is this correct?

No.

A fermented food may contain microorganisms, but a probiotic designation requires evidence that specific live microorganisms provide a health benefit when consumed in adequate amounts.

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Worked Example 8

A sourdough starter contains both yeast and lactic acid bacteria.

What does each contribute?

Yeast → carbon dioxide and other fermentation products

Lactic acid bacteria → acids and flavor compounds

Together they contribute to the bread's texture and flavor.

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Worked Example 9

Why must industrial food fermentations control temperature?

Microbial enzymes function best within particular temperature ranges.

If conditions are too cold:

fermentation slows.

If conditions become too hot:

microbial cells or enzymes may be damaged.

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Worked Example 10

Why can beneficial microorganisms help preserve food?

They can produce substances such as:

acids or ethanol

and compete with unwanted microorganisms.

These conditions can make it harder for some spoilage organisms and pathogens to grow.

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Comparing Useful and Harmful Microorganisms

Useful microorganisms

May:

• produce food
• improve flavor
• improve texture
• preserve food
• produce useful enzymes

Examples:

yeast and lactic acid bacteria

Harmful microorganisms

May:

• cause disease
• spoil food
• produce toxins

Examples include certain foodborne:

pathogens and toxin-producing microorganisms.

The goal of food biotechnology is to encourage useful microorganisms while controlling harmful ones.

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Common Mistake: All Bacteria Are Harmful

Many bacteria are harmless or beneficial.

Lactic acid bacteria are essential in producing foods such as:

yogurt and many cheeses.

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Common Mistake: All Microorganisms Cause Food Spoilage

Some microorganisms spoil food.

Others are deliberately used to:

produce food.

The effect depends on the microorganism and conditions.

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Common Mistake: Fermentation Is Only Used to Produce Alcohol

Fermentation is used to produce:

• bread
• yogurt
• cheese
• fermented vegetables
• soy products
• vinegar
• many other foods

Alcohol production is only one application.

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Common Mistake: Refrigeration Kills All Bacteria

Refrigeration generally:

slows microbial growth.

It does not sterilize food.

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Common Mistake: Any Mold on Food Is the Same as Cheese Mold

Specific molds are deliberately selected for particular food-production processes.

Random mold growing on food may be:

unsafe.

Never assume that unwanted mold is harmless because some cheeses are intentionally produced using fungi.

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Common Mistake: Fermented Means Probiotic

These terms are not interchangeable.

Fermented describes a microbial process used to transform food.

Probiotic describes specific live microorganisms that have demonstrated health benefits when consumed in adequate amounts.

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Check Your Understanding

1. What is food biotechnology?

2. What role do microorganisms play in food production?

3. Give five foods produced using microorganisms.

4. What type of microorganism is yeast?

5. What process does yeast use when making bread?

6. What gas causes bread dough to rise?

7. Explain how yeast causes bread to rise.

8. Why does dough rise more slowly at low temperatures?

9. What type of microorganisms are used to produce yogurt?

10. What substance do these microorganisms produce?

11. Explain why yogurt becomes acidic.

12. Why does yogurt become thicker during fermentation?

13. What is a starter culture?

14. How are bacteria used in cheese production?

15. How can fungi be useful in cheese production?

16. Explain how fermented vegetables are produced.

17. How does lactic acid help preserve food?

18. How can ethanol contribute to preservation?

19. What role can salt play during vegetable fermentation?

20. Explain how beneficial microorganisms can compete with unwanted microorganisms.

21. What is a probiotic?

22. Why is not every fermented food automatically probiotic?

23. What is food contamination?

24. Give four possible sources of microbial contamination.

25. Why is temperature control important during food production?

26. Explain why refrigeration does not sterilize food.

27. What is pasteurization?

28. How does pasteurization differ from sterilization?

29. Why is hygiene important in microbial food production?

30. Give three benefits of using microorganisms in food production.

31. Give three possible risks.

32. Explain how microbial food production can extend storage life.

33. How can microorganisms change the flavor of food?

34. How can microorganisms change food texture?

35. Describe the microorganisms found in a typical sourdough starter.

36. Explain how sourdough demonstrates cooperation between different microorganisms.

37. Give three examples of microbial biotechnology that you might encounter in an ordinary kitchen.

38. Explain why a useful microorganism in one situation could be considered a spoilage organism in another.

39. Evaluate the benefits and risks of using microorganisms to produce food.

40. Explain why food fermentation can be described as both an ancient technology and a modern form of biotechnology.

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Key Terms

• Food biotechnology: Use of organisms, cells, enzymes, or biological processes to produce or modify food.
• Fermentation: Microbial or cellular process that converts nutrients into other products under particular metabolic conditions.
• Yeast: Single-celled fungus used in foods such as bread.
• Lactic acid bacteria: Bacteria that produce lactic acid during fermentation.
• Starter culture: Selected microorganisms added to begin controlled fermentation.
• Lactic acid: Acid produced by certain bacteria during fermentation.
• Food preservation: Processes used to slow food spoilage and maintain food safety or quality.
• Cross-contamination: Transfer of microorganisms or contaminants from one food, surface, or object to another.
• Contamination: Introduction of unwanted microorganisms or other harmful substances.
• Pathogen: Disease-causing organism or infectious agent.
• Pasteurization: Controlled heating used to reduce important pathogens and spoilage microorganisms.
• Refrigeration: Use of low temperature to slow microbial and chemical activity.
• Probiotic: Live microorganism that provides a demonstrated health benefit when administered in adequate amounts.
• Microbiota: Community of microorganisms living in a particular environment.
• Bioreactor: Controlled vessel used to grow microorganisms or cells.
• Quality control: Procedures used to ensure products meet required standards.
• Mycotoxin: Harmful substance produced by certain fungi.
• Foodborne disease: Illness caused by consuming contaminated food or drink.

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Key Takeaways

• Microorganisms are widely used in food production.
• Food biotechnology includes the controlled use of microorganisms and their enzymes.
• Fermentation is one of the oldest forms of biotechnology.
• Yeast produces carbon dioxide that causes bread dough to rise.
• Lactic acid bacteria are used to produce yogurt, cheese, and fermented vegetables.
• Selected molds are deliberately used to produce some cheeses.
• Microorganisms are also involved in products such as soy sauce and vinegar.
• Fermentation can preserve food by producing acids, ethanol, and other substances that inhibit unwanted microorganisms.
• Useful microbes can also compete with spoilage organisms for nutrients.
• Salt, acidity, refrigeration, and microbial competition can work together to preserve fermented foods.
• Microorganisms create many of the flavors and textures associated with fermented foods.
• Not all microorganisms are harmful; many are essential to food production.
• Not all microorganisms are beneficial either, so contamination control is essential.
• Specific foodborne pathogens and toxin-producing microorganisms can make food unsafe.
• Temperature, pH, hygiene, and storage conditions must be carefully controlled.
• Refrigeration slows microbial growth but does not sterilize food.
• Pasteurization reduces important pathogens and spoilage organisms but is not the same as sterilization.
• Not every fermented food is automatically a probiotic food.
• Microbial food production provides benefits including preservation, food variety, flavor development, and useful nutritional changes.
• Potential risks include contamination, spoilage, toxin production, and foodborne disease.
• Foods such as bread, yogurt, cheese, sourdough, fermented vegetables, vinegar, and soy sauce make biotechnology part of everyday life.
• Food fermentation shows how humans can use microbial metabolism in controlled ways to produce useful products.