Food Proteins - Soy

Question 1

What food properties are organoleptic?

Answer 1

Colour
Odour
Flavour
Texture

Question 2

What food properties are hydration?

Answer 2

Water holding capacity

Solubility

Question 3

What food properties are rheological?

Answer 3

Aggregation
Elasticity
Viscosity

Question 4

What food properties are surface?

Answer 4

Emulsification

Foaming

Question 5

What is soya?

Answer 5

A hairy stemmed plant of the legume family

Question 6

Give two examples of non-fermented soy.

Answer 6

Tofu

Soy milk

Question 7

Given an example of fermented soy.

Answer 7

Soy sauce

Question 8

How is tofu produced?

Answer 8

1. Soak soy beans overnight in water
2. Grind soy beans
3. Cook soy beans with added fresh water (produces soy milk)
4. Coagulation with calcium and magnesium salts (produces curds and whey)
5. Whey is drained off
6. Curds are pressed in a cheesecloth

Question 9

How is soy sauce produced?

Answer 9

Production of a fermented paste from soy beans, brine and roasted grain
Pressing of the paste produces a liquid which is soy sauce

Question 10

What is the fermented paste produced in soy sauce production fermented by?

Answer 10

Aspergillus

Question 11

What types of molecules do soy beans contain?

Answer 11

Protein 
Oil 
Insoluble and soluble carbohydrates
Vitamins B and E
Phytochemicals 
Phosphorous 
Potassium 
Zinc 
Iron

Question 12

What other proteins are soy proteins similar to in terms of protein value?

Answer 12

Eggs proteins
Milk proteins
Meat proteins
Soy = a cheap replacement

Question 13

What amino acids do soy proteins contain?

Answer 13

A complete range of essential amino acids

Question 14

What are the two main soy proteins?

Answer 14

Beta-conglycinin and glycinin

Question 15

What is beta-conglycinin and what is its structure?

Answer 15

Glycoprotein
3 subunits
- Alpha '
- Alpha 
- Beta

Question 16

What is the structure of glycinin?

Answer 16

Hexamer = 6 subunits
- 1a 
- 1b 
- 2
- 3
- 4
- 5
All linked by disulphide bonds

Question 17

How do beta-conglycinin and glycinin differ?

Answer 17

In their gel formation
Beta-conglycinin = soft, transparent, elastic gels
Glycinin = turbid, hard gels

Question 18

How are soy concentrates produced?

Answer 18

1. Clean, crack and hull soy beans
2. Heat and flake
3. Hexane extraction
4. Vapour desolventise
5. Remove sugars
6. Grind
7. Moisten
8. Dry

Question 19

How is soy flour produced?

Answer 19

1. Clean, crack and hull soy beans
2. Heat and flake
3. Hexane extraction
4. Vapour desolventise
5. Grind
6. Moisten
7. Dry

Question 20

How are soy isolates produced?

Answer 20

1. Clean, crack and hull soy beans
2. Heat and flake
3. Hexane extraction
4. Vapour desolventise
5. Protein solubilizing
6. Precipitation with acid at isoelectric point
7. Separation of protein flakes
8. Spray drying

Question 21

What are the uses of soy proteins?

Answer 21

Soy flour = bakery
Soy concentrates = bakery, dairy products, meat products
Soy isolates = products used to replace or reinforce (meat substitutes, improve nutritional quality)

Question 22

What are the functional properties of soy proteins?

Answer 22

• High water holding capacity
• Pasty gel formation
• Fat binding emulsifiers
• Extrusion under high pressure produces pieces resembling dry meat