5.1.5 Bacteria in Food Production

Question 1

Microorganisms can be used by humans to produce what?

Answer 1

Foods and other useful substances

Question 2

As well as fungi (e.g. yeast used to make bread), what is also used in the production of certain foods?

Answer 2

Bacteria

Question 3

Bacteria are useful because they are capable of producing what?

Answer 3

Complex molecules

e.g. certain bacteria added to milk produce enzymes that turn the milk into yoghurt

Question 4

They are also useful because they reproduce how?

Answer 4

Rapidly.

the amount of chemicals they can produce can also rapidly increase

Question 5

Yoghurt is made in a process that relies on the presence of a specific type of bacterium called what?

Answer 5

Lactobacillus

Question 6

First, all equipment is sterilised to kill other, unwanted bacteria and to prevent what?

Answer 6

chemical contamination

Question 7

Milk is then pasteurised (heated) to kill other unwanted bacteria at what temperature?

Answer 7

85-95°C

Question 8

Contamination with other bacteria could slow what?

Answer 8

The production of the yoghurt

(by competing with the Lactobacillus for the lactose in the milk).
It could also spoil the taste of the yoghurt

Question 9

The milk is then cooled and Lactobacillus bacteria is added at what temperature?

Answer 9

40-45°C

Question 10

The mixture is incubated at this temperature for how long?

Answer 10

Several hours

while the Lactobacillus bacteria digest milk proteins and ferment (digest) the sugar (i.e. the lactose) in the milk

Question 11

The Lactobacillus bacteria convert the lactose into lactic acid and what?

Answer 11

This increased acidity sours and thickens the milk to form yoghurt

Question 12

This lowering of the pH also helps to prevent the growth of other what?

Answer 12

Microorganisms that may be harmful, so acts as a preservative

Question 13

Lowering the pH means the yoghurt can be kept for a longer time compared to what?

Answer 13

Fresh milk

Question 14

The yoghurt is then stirred and cooled to 5°C to halt the action of what?

Answer 14

The Lactobacillus bacteria

Question 15

What may be added before packaging?

Answer 15

Flavourings, colourants and fruit

Question 16

Fermenters are containers used to grow (‘culture’) microorganisms in large amounts like what?

Answer 16

Bacteria and fungi

Question 17

Fermenters are used for what 3 products?

Answer 17

Brewing beer
making yoghurt
mycoprotein

Question 18

What 2 products, not involving food, us this process?

Answer 18

Genetically modified bacteria and moulds that produce antibiotics (e.g. penicillin)

Question 19

The advantage of using a fermenter is that conditions can be carefully controlled to what?

Answer 19

Produce large quantities of exactly the right type of microorganism

Question 20

Aseptic precautions is the a condition, how is it controlled?

Answer 20

Fermenter is cleaned by steam to kill microorganisms and prevent chemical contamination, which ensures only the desired microorganisms will grow

Question 21

Nutrients are the a condition, how is it controlled?

Answer 21

Nutrients are needed for use in respiration to release energy for growth and to ensure the microorganisms are able to reproduce

Question 22

Optimum temperature is the a condition, how is it controlled?

Answer 22

Temperature is monitored using probes and maintained usin the water jacket to ensure an optimum environment for enzymes to increase enzyme activity (enzymes will denature if the temperature is too high or work too slowly if it is too low)

Question 23

Optimum pHis the a condition, how is it controlled?

Answer 23

pH inside the fermenter is monitored using a probe to check if it is at the optimum value for the particular microorganism being grown. The pH can be adjusted, if necessary, using acid or alkalis.

Question 24

Oxygenation is the a condition, how is it controlled?

Answer 24

Oxygen is needed for aerobic respiration to take place

Question 25

Agitation is the a condition, how is it controlled?

Answer 25

Stirring paddles ensure that microorganisms, nutrients, oxygen, temperature and pH are evenly distributed throughout the fermenter