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Unit 7: Genes and inheritance

Microorganisms in food production — HIA International - Grade 8 Revision Notes & Topical Questions

5 min read 10 parts Lesson 5 of 9 1 quiz

📚 HIA International - Grade 8 Hub / Topical Revision
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Lesson summary

Microorganisms in food production — HIA INTERNATIONAL notes: Name the microorganisms used to make food and describe how yeast and bacteria are used in bread, drinks, yoghurt and cheese.Microorganism = a living organism so small it can only be seen clearly with a microscope.Bacter…

  • Microscopic fungi
  • Protozoa and algae
  • When there is little oxygen, yeast respires without oxygen
  • The useful product is ethanol (alcohol)
  • Blue cheeses
  • Mycoprotein (Quorn)

Part 1 of 8Kinds of microorganism

Kinds of microorganism
Microorganism
Microorganism a living organism so small it can only be seen clearly with a microscope.
Bacteria
  • Bacteria single-celled organisms much smaller than animal or plant cells; most are harmless.
Microscopic fungi
  • Microscopic fungi for example yeast, which is single-celled and reproduces by budding.
Protozoa and algae
  • Protozoa and algae other microscopic organisms, found in pond water.
Colony
  • Colony a visible group of cells formed when one bacterium or fungus cell divides repeatedly.

Part 2 of 8Yeast and fermentation

Yeast and fermentation
Yeast
  • Yeast a single-celled fungus that feeds on sugar.
When there is little oxygen, yeast respires without oxygen
  • When there is little oxygen, yeast respires without oxygen this is called fermentation.
Word equation: glucose → ethanol + carbon dioxide.
  • Symbol equationC6H12O6 → 2C2H5OH + 2CO2.
Yeast works best warm (about 25–40 °C) with sugar and water.
Too cold slows respiration.
  • Above about 50 °C the yeast is killed because its enzymes are denatured.

Part 3 of 8Making bread

1
Mix flour, water, sugar and yeast to make dough.
2
Leave the dough in a warm place.
3
Yeast ferments the sugar and produces carbon dioxide.
4
Carbon dioxide bubbles make the dough rise.
5
Baking kills the yeast, sets the bread and evaporates the small amount of ethanol.

Part 4 of 8Making drinks

1Brewing
  • Brewing yeast ferments sugars from grapes (wine) or barley (beer).
2The useful product is ethanol (alcohol)
  • The useful product is ethanol (alcohol) the carbon dioxide escapes or makes the drink fizzy.

Part 5 of 8Making yoghurt

1
Heat milk to about 85 °C to kill unwanted microorganisms.
2
Cool the milk to about 40–45 °C.
3
Add a starter culture of lactic acid bacteria (for example Lactobacillus).
4
Keep the mixture warm for several hours.
5
The bacteria turn lactose (milk sugar) into lactic acid, which thickens the milk and makes it taste sour.
6
Refrigerate to slow further bacterial growth.

Part 6 of 8Cheese and other foods

Cheese
  • Cheese bacteria sour the milk and an enzyme (rennet) makes it separate into solid curds and liquid whey.
Blue cheeses
  • Blue cheeses moulds are added during ripening.
Mycoprotein (Quorn)
  • Mycoprotein (Quorn) made from a fungus.
Soy sauce and vinegar
  • Soy sauce and vinegar made by fermentation with fungi and bacteria.
Industrial production
  • Industrial production microorganisms are grown in large sterile fermenters with controlled temperature, pH and nutrients.

Part 7 of 8Spoilage and preservation

Spoilage and preservation
Spoilage
  • Spoilage bacteria and moulds grow on food and make it decay.
Some produce toxins that cause food poisoning.
  • They grow best in warm, moist conditions with nutrients.
Preservation slows or stops microbial growth
  • Preservation slows or stops microbial growth cold, heating or pasteurising, drying, salt or sugar, pickling in acid and canning.

Part 8 of 8More from the specification

Microorganisms
  • Microorganisms yeast and bacteria are used in food production because their metabolism makes useful products.
Yeast fermentation
  • Yeast fermentation yeast respires anaerobically, producing carbon dioxide that makes bread rise and ethanol in brewing.
Bacteria in dairy
  • Bacteria in dairy lactic acid bacteria ferment milk sugar to make yoghurt and cheese.
Food chains
  • Food chains energy passes from plants through consumers, and decomposers return nutrients to the environment.
Models
  • Models scientists use models, such as food chain diagrams, to explain and predict how living systems work.
Microorganisms
  • Microorganisms yeast and bacteria are used in food production because their metabolism makes useful products.
Yeast fermentation
  • Yeast fermentation yeast respires anaerobically, producing carbon dioxide that makes bread rise and ethanol in brewing.
Bacteria in dairy
  • Bacteria in dairy lactic acid bacteria ferment milk sugar to make yoghurt and cheese.
Food chains
  • Food chains energy passes from plants through consumers, and decomposers return nutrients to the environment.
Models
  • Models scientists use models, such as food chain diagrams, to explain and predict how living systems work.
Eclipse
  • When one body blocks light and casts a shadow on another.
Decomposer
  • An organism that breaks down dead matter.
Organic matter
  • Any substance made by a living organism.
Solar eclipse
  • The Moon blocks light from the Sun to Earth.
Lunar eclipse
  • The Earth blocks light from the Sun to the Moon.

Key terms

TermMeaning
FermentationRespiration without oxygen by microorganisms, such as yeast making ethanol and carbon dioxide from sugar.
YeastA single-celled fungus used to make bread and alcoholic drinks.
BacteriaSingle-celled microorganisms, some of which make yoghurt and cheese.
Lactic acidThe acid made by bacteria from lactose that thickens milk.
PasteurisationHeating milk to kill harmful microorganisms.
ColonyA visible group of microorganism cells grown from one cell.
FermenterA large sterile vessel in which microorganisms are grown for food production.
EnzymeA protein that speeds up a chemical reaction.

Avoid these mistakes

1
Saying yeast makes bread rise by producing oxygen — it produces carbon dioxide.
2
Thinking all microorganisms are harmful — many are used to make food and drink.
3
Saying yeast is killed by cold — cold slows it, while high temperatures kill it.
4
Saying bacteria make bread rise — bread is made with yeast, whereas bacteria make yoghurt and cheese.

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