6.4.5: Using biotechnology to make food.

Question 1

Outline the process of making yoghurt.

Answer 1

• Yoghurt fermented by lactobacillus and s.thermophillis bacteria.
• Acidity denatures milk protein, coagulates.
• Bacteria partially digest milk, making it easy to digest.
• Fermentation also produces flavour (sour).
• Other bacteria may be added as probiotics.

Question 2

What are probiotics?

Answer 2

• Bacteria which may benefit human health.
• Improve digestion of lactose.
• Aid gastrointestinal function.
• Stimulate immune system.

Question 3

Outline the process of making cheese.

Answer 3

• Milk pre-treated with bacteria that produces lactic acid from lactose.
• Once acidified, milk mixed with rennet.
• Rennet contains enzyme rennin which coagulates milk protein(casein) in presence of calcium ions.
• Resulting solid (curd) separated from liquid (whey) by cutting, stirring, heating.
• Bacteria continue to grow, producing more lactic acid.
• Curd pressed into moulds.

Question 4

What are the two steps in the coagulation of the milk protein (casein) in the presence of calcium ions?

Answer 4

1. Kappa-casein, which keeps casein in solution is broken down, this makes casein insoluble.
2. The casein is precipitated by the action of calcium ions, which bind the molecules together,

Question 5

What determines the characteristics of the cheese?

Answer 5

-Treatment while making and pressing the curd.

Question 6

What determines the flavour of the cheese?

Answer 6

• Determined during the later ripening and maturing process.
• Inoculation with fungi to produce ‘blue cheese’.

Question 7

What are the three key stages in baking?

Answer 7

1. Mixing: ingredients mixed by kneading, this produces the dough.
2. Proving/fermenting: Dough left in warm place for up to three hours while yeast respires anaerobically. This produces CO2 bubbles which cause the dough to rise.
3. Cooking: The risen dough is baked. Any alcohol evaporates during the cooking process.

Question 8

How is wine made?

Answer 8

• Using grapes that naturally have yeast on their skin.
• Grapes contain sugars, fructose and glucose.
• When crushed, yeast uses these sugars to produce alcohol and CO2.

Question 9

How is Quorn made?

Answer 9

-Using microorganisms that produce proteins that are used directly as food.

Question 10

What are the advantages to single-cell protein using microorganisms?

Answer 10

• No animal fat or cholesterol.
• Produces protein with a similar amino acid profile to animal and plant protein.
• Can grow on almost any substrate, including waste material such as paper and whey.
• Not much land required.
• Production faster thab animal or plant protein.

Question 11

What are the disadvantages to single-cell protein using microorganisms?

Answer 11

• Don’t want to eat fungal protein.
• microorganisms need to be isolated from the material on which they grow.
• Protein needs to be purified (ensure uncontaminated)
• Microbial biomass can have a high proportion nucleic acids which must be removed.
• Amino acid profile different to animal protein (deficient in methionine).
• Conditions are ideal for pathogenic organisms. Care must be taken to prevent culture from being infected.
• Doesn’t taste the same as traditional protein source.