Microorganisms and Food Worksheet

Microorganisms - germs - surely they're all bad?

In fact, the vast majority are beneficial (good) for life on our planet. Actually, they are absolutely vital because without them, nothing that dies (like leaves in autumn) would be broken down and re-used.

This worksheet looks at how microorganisms affect our food; both in terms of how they are used in food production and how they need to be considered in food hygiene, so that the harmful ones don't end up making us ill.

Cheese is made from milk which has been heated and then had ingredients added to make a particular sort of cheese. Which of these microorganisms is NOT used in cheese production?

fungi

bacteria

viruses

Like cheese, yogurt is made from milk which has been treated. Which microorganisms is used in yogurt-making?

fungi

bacteria

viruses

When beer is made (by fermentation) a certain type of microorganism is added to produce the alcohol. Which microorganism is that?

bacteria

salmonella

yeast

Yeast is used in bread-making. What is its function in bread production?

it stops the bread from going bad

it adds flavour to the bread

it makes the bread rise

Which of these food-related problems is caused by a fungus?

salmonella

mould

E.coli

Which of these foods sometimes contains the harmful microorganism salmonella (meaning that you always have to store it correctly to avoid this)?

raw chicken

brown bread

fish

We are lucky in the UK because the water that comes out of our taps is safe to drink. However, in some countries the people are not so fortunate because the water contains microorganisms and is unsafe to drink without treating it first.

What could you do to make it safe to drink?

boil it

filter it

leave it in a cup for a few days to allow any dirt to settle to the bottom

What is the name of the process that is used to make milk last longer without going off but which doesn't kill the harmless microorganisms in it?

sterilisation

pasteurisation

immunisation

Which of these conditions are best for the rapid growth of microorganisms like bacteria?

warm and dry

warm and moist

cold and dry

cold and moist

hot and dry

hot and moist

What is the name of the process that kills all microorganisms?

cleaning

purification

sterilisation

ANSWERS

Question 1

Cheese is made from milk which has been heated and then had ingredients added to make a particular sort of cheese. Which of these microorganisms is NOT used in cheese production?

CORRECT ANSWER

viruses

EDDIE SAYS

Certain bacteria are added to milk to make cheese and for blue cheese, like Stilton, fungi gives the distinctive blue veins throughout the cheese.

ANSWERS

Question 2

Like cheese, yogurt is made from milk which has been treated. Which microorganisms is used in yogurt-making?

CORRECT ANSWER

bacteria

EDDIE SAYS

Milk has yogurt-making bacteria added to it so that it turns into yogurt. Then you can add different fruits to make your own exciting flavours, like mango and blueberry - yum!

ANSWERS

Question 3

When beer is made (by fermentation) a certain type of microorganism is added to produce the alcohol. Which microorganism is that?

CORRECT ANSWER

yeast

EDDIE SAYS

Yeast is a type of fungi (like mushrooms) which is microscopic. It is a living thing which multiplies and grows in the beer mixture. It carries out a process called respiration to make energy and produces carbon dioxide (a gas) and alcohol as waste products.

ANSWERS

Question 4

Yeast is used in bread-making. What is its function in bread production?

CORRECT ANSWER

it makes the bread rise

EDDIE SAYS

'Yeast is a microorganism that's well and truly alive, which means that it respires just like you! So that means that it releases carbon dioxide and the bubbles of gas make the bread rise and become light and fluffy (instead of flat, heavy and hard).

ANSWERS

Question 5

Which of these food-related problems is caused by a fungus?

CORRECT ANSWER

mould

EDDIE SAYS

Mould on bread or jam is caused by a fungus that spreads by tiny seed-like particles called spores. Both salmonella and E.coli are bacteria that cause food scares from time-to-time.

ANSWERS

Question 6

Which of these foods sometimes contains the harmful microorganism salmonella (meaning that you always have to store it correctly to avoid this)?

CORRECT ANSWER

raw chicken

EDDIE SAYS

Salmonella is a harmful microorganism (a type of bacteria this time) that is often associated with chicken and eggs. With correct handling and storage procedures it does not usually present a problem.

ANSWERS

Question 7

We are lucky in the UK because the water that comes out of our taps is safe to drink. However, in some countries the people are not so fortunate because the water contains microorganisms and is unsafe to drink without treating it first.

What could you do to make it safe to drink?

CORRECT ANSWER

boil it

EDDIE SAYS

Boiling it is the best course of action if you are unsure about the water - that will kill most of the harmful microorganisms.

ANSWERS

Question 8

What is the name of the process that is used to make milk last longer without going off but which doesn't kill the harmless microorganisms in it?

CORRECT ANSWER

pasteurisation

EDDIE SAYS

Louis Pasteur was a French scientist who lived in the 19th century and developed a process that helps milk last longer safely but that does not kill off the useful microorganisms in it, so it's called 'pasteurisation' after him.

ANSWERS

Question 9

Which of these conditions are best for the rapid growth of microorganisms like bacteria?

CORRECT ANSWER

warm and moist

EDDIE SAYS

Bacteria love it when the temperature soars to about 30°C (like a really boiling summer's day in the UK) and as long as there's lots of food and water they will reproduce really rapidly (that's one of the reasons that perishable food's kept in the fridge - the cold temperature slows the microorganisms right down).

ANSWERS

Question 10

What is the name of the process that kills all microorganisms?

CORRECT ANSWER

sterilisation

EDDIE SAYS

A sterile environment (such as in a hospital operating theatre) is one where there are no microbes at all - they have all been killed. Sterilisation is often achieved by the use of heat or certain chemicals (like disinfectants).