M22. Food

Question 1

What are the 4 main ways that/micro organisms can spoil our food

Answer 1

• visual growth of microorganisms on food, eg fungi
• micro organisms use an external digestion process
• The bacterium Clostridium botulinum produces a toxin called botulin
• The presence of the microorganismsin food can cause infection

Question 2

give an example of visual growth of microorganisms on our food?

Answer 2

This is most obvious when fungi grow on food. For example, colonies of moulds Mucor and Penicilium often grow on bread. This mould has usually been growing for a few days before it becomes noticeable as either black (Mucor) or blue/green (Penicillium) mould.

Question 3

How do microorganisms use external digestion processes to spoil food??
What effect does this have on the food?

Answer 3

They release enzymes into the food and absorb the nutrients released by breaking down the food molecules.
When this happens food usually smells sweet as sugar is released from carbohydrate molecules and the food will eventually be reduced to a mush by the action of the enzymes

Question 4

What is the effect when The bacterium Clostridium botulinum produces a toxin called botulin?

Answer 4

It causes botulism. If these bacteria are growing on food, the toxin will be present, that is one of the most toxic known toxins- just 1ug can kill a person

Question 5

Give an example of how The presence of the microorganismsin food can cause infection can cause food spoilage

Answer 5

Eg the Salmonella bacteria, sometimes present in poultry products, attack the lining of the stomach and digestive system.

Question 6

Name 8 methods of preventing food spoilage

Answer 6

• Eating food quickly while its fresh
• cooking
• pasteurising
• drying/ salting/ covering in sugar
• smoking
• pickling
• irradiation
• cooling/freezing

Question 7

How does cooking prevent food spoilage?

Answer 7

the heat denatures enzymes or other proteins and kills the micro organisms

Question 8

How does pasteurising prevent food spoilage?

Answer 8

by heating to 72 degrees for 15 seconds then cooling rapidly to 4 degrees kills any harmful micro organisms.

Question 9

How does drying/salting/covering food in sugar prevent food spoilage?

Answer 9

As this dehydrates microorganisms as water leaves them via osmosis

Question 10

How does smoking prevent food spoilage?

Answer 10

As the food developed a hard, dry outer surface and the smoke contains antibacterial chemicals.

Question 11

How does pickling prevent food spoilage?

Answer 11

as it uses acid pH to kill micro organisms by denaturing their enzymes and other proteins.

Question 12

How does irradiation prevent food spoilage?

Answer 12

as the ionising radiation kills the micro organisms by disrupting their DNA structure

Question 13

How does cooling or freezing prevent food spoilage

Answer 13

As although this does not kill micro organisms, but it retards enzyme activity so their metabolism, growth rate and reproduction is very very slow.

Question 14

How can canning prevent contamination?

Answer 14

As the food is heated and then placed in an airtight container

Question 15

How can contamination be prevented further?

Answer 15

• canning
• vacuum wrapping
• plastic/paper packaging.

Question 16

How can vacuum wrapping products prevent further contamination/

Answer 16

air is excluded so microbes cant respire aerobically.

Question 17

Give 4 examples of how micro organisms are used to make food

Answer 17

• Yoghurt is milk that has been affected by Lactobacillus bacteria
• Cheese has made from curdled milk
• Bread is risen by yeast
• Alcohol is produced when yeast respires anaerobically.

Question 18

How is yoghurt made?

Answer 18

The lactobacillus bacteria uses the lactose sugar in milk to make lactric acid, which causes the milk protein to thicken. The bacteria partially digests the milk, making it easily digestible for humans

Question 19

Why is yoghurt beneficial?

Answer 19

As it helps to ensure that our digestive system contains the non-pathogenic bacteria it needs to aid digestion

Question 20

How is cheese made?

Answer 20

The solid part of the milk (curds) is acted upon by Lactobacillus bacteria, and these cheese is given extra flavour by contamination with fungi such as Penicillium to produce blue cheese.

Question 21

What causes bread to rise?

Answer 21

As yeast respired anaerobically, carbon dioxide is produce, causing bubbles of gas which causes the dough to rise.

Question 22

How is alcohol produced?

Answer 22

Due to the anaerobic respiration of yeast.

Grapes contain the

Question 23

How is beer made?

Answer 23

Cereal grains containing the sugar maltose can be used to brew beer, as the yeast respires the sugar.

Question 24

How is wine made?

Answer 24

Grapes contain the sugars fructose and glucose, which the yeast uses in making wine.

Question 25

Give an example of microorganisms that have been used to produce a protein?

Answer 25

The single celled protein (SCP), the best known type is Quorn, a mycoprotein- a protein made by fungus

Question 26

Why is Quorn thought to be a healthier option to meat?

Answer 26

As it contains no animal fat or cholesterol.

Question 27

Why is there such a great potential in SCP production using micro organisms such as Kluyveromyces, Scytalidium and Candida.

Answer 27

As they can produce protein with similar amino acid profiles to animal and plant protein
And they can grow on almost any organic substrate including waste materials such as paper and whey.

Question 28

Name 6 advantages of using micro organisms to produce SCP

Answer 28

• Production of protein can be many times faster than that of an animal or plant protein.
• Production can be increase and decreased easily according to demand.
• There are no animal welfare issues
• Good source of protein for vegetarians
• Contains no animal fat or cholesterol
• SCP production could be combined with the removal of waste products like whey

Question 29

Name 5 disadvantages of using micro organisms to produce SCP

Answer 29

• many people may not want to eat fungal protein/food that has been grown on waste
• isolation of the protein, the micro organisms are grown in huge fermenters and need to be isolated from the material on which they grow
• the protein has to be purified to ensure it hasnt been contaminated
• infection is a risk due to ideal conditions
• Palatability, (the protein does not have the same taste or texture of traditional protein sources.

Question 30

Why is infection a high risk in the production of SCP?

Answer 30

the conditions needed for the useful microorganisms to grow are also ideal for pathogenic organisms so care must be taken to ensure the culture is not infected with the wrong organisms`

Question 31

What is palatability?

Answer 31

the fact that the protein does not have the same taste or texture of traditional protein sources.