BMS1064 - Food proteins

Question 1

Give examples of fermented and non-fermented soy foods.

Answer 1

Fermented: soy sauce

non-fermented: tofu and soymilk

Question 2

What nutrients do soybeans contain?

Answer 2

38% proteins
18% Oil
15% insoluble and 15% soluble CHOs

Phosphorus, potassium, zinc, iron, vitmain BE

HIgh amount of phytochemicals -> lowered cholesterol and b.p., improed bone health, easing of menstrual symptoms

Question 3

Why is using soy protein good?

Answer 3

High availability
Complete range of essential AAs
Affordable

Question 4

Around 90% of soybean proteins exist as storage proteins. These mostly consist of ________ and ______. These differ in gel formation.

_________ makes transparent, soft elastic gels
_________ makes turbid, hard gels.

Answer 4

beta-conglycinin
glycinin

beta-conglycinin
glycinin

Question 5

What is soy protein isolate?

Answer 5

The most refined type of protein.
Fat, fibre and sugars removed.

Question 6

What is soy protein concentrate? What is it used in usually?

Answer 6

More refined than soy flour, but less refined than soy protein isolate.
Had sugars removed.

Bakery and dariy/meat products

Question 7

What are the functional uses of soy protein?

Answer 7

High water holding capacity.

Gelation -> soups, meat, bakery, sauces

Emulsification -> meat, bakery, confectionary

Texturisation (extrusion under high P/T, giving pieces resembling dried meat) -> meat extenders/replacers

Question 8

Give an overview of egg composition. What are the key proteins?

Answer 8

Egg White (Albumen) - 87% water, 10-12% proteins

Key proteins: Ovalbumin, Ovotransferrin, Lysozyme, Ovomucin

Egg yolk - rich in lipids and proteins
Contrains LDL, HDL and phospholipids - essential for emulsification

Question 9

What are the functional properties of egg proteins?

Answer 9

Foaming

Gelation

Emulsification

Antimicrobial

Question 10

Why are eggs good for foaming? What is the mechanism?

Answer 10

Proteins stabilize air bubbles

e.g. meringues

Mechanism: proteins unfold and form a cohesive film around air bubbles.

Proteins contributing to foaming:
- globulins and ovalbumin are the most surface-active
- lysozyme and ovomucin enhance foam stability through electrostatic interactions

Question 11

How does gelation of egg proteins work? What varies? What can be changed to modify the gels?

Answer 11

Heat denatures egg proteins, leading to gel formation.

e.g. custards, quiches

Denaturation temperature varies - e.g. overtransferrin denatures first, then ovalbumin

Adjusting pH and salt concs can modify gel hardness and transparency

Question 12

Which part of the egg acts as a natural emulsifier? What doe s it contain? What type of mixtures does it stabilise?

Answer 12

Egg yolk as its rich in lecthin. Also high in phospholipids and lipoproteins.

These stabilizes oil-water mixtures

e.g. sauces, ice cream

Question 13

What aspect in eggs leads to it antimicrobial property?

Answer 13

Lysozyme - targets bacterial wall
Ovotransferrin - inhibits growth

Question 14

What are 4 ways egg proteins can be processed and modified?

Answer 14

Drying -> powdered forms

Enzymatic -> phospholipase enhances yolk emulsification, extends shelf life

Heat treatment -> gels, microbial safety

Desugarisation -> removed sugars to prevent Maillard browning

Question 15

Give an example of how egg proteins used in functional foods.

Answer 15

IRON FORTIFIED FOODS

Ovotransferrin used in beverages and supplements to improve iron bioavailability.

Question 16

What are some other innovations and applications of egg proteins?

Answer 16

Microencapsulation -> stabilizes vitamins, probiotics etc

Plant-based innovations -> plant/egg protein hydrbrid products

Question 17

What is an emulsion?

Answer 17

A liquid dispersed in small droplets (disperse phase) in another liquid (continuous phase).

Question 18

What are the 2 main types of emulsion?

Answer 18

Water in oil -e.g. butter/margarine

Oil in water -e.g. mayonnaise

(More complex ones include W/O/W or O/W/O)

Question 19

How is an emulsion made?

Answer 19

Homogenise (blend/mix) 2 liquids
Add biopolymer to stabalise.

Question 20

What is a foam?

Answer 20

A dispertion of gas bubbles in a liquid

e.g. beer, bread, meringues

Question 21

Give examples of emulsifying agents.

Answer 21

Proteins, phospholipids (egg yolk)
Sterols, esters of FAs, glyceryl monostearate (GMS)

Question 22

What are the properties of emulsifiers?

Answer 22

Polar and non-polar groups
- adsorb at the interface and form a monloayer.
- lower the surface tention

Question 23

A good emulsifier does what?

Answer 23

• High rate at which it penetratrates into O/W interface
• Decreases interfacial tension
• Decreases energy required to produce particle size
• Low contact angle

Question 24

Why should surface tension be lowered in emulsions?

Answer 24

To increase surface area - many small droplets

Question 25

The contact angle made by the emulsifier at interface will promote either ______ or ______ emulstions.

Answer 25

W/O or O/W

Question 26

The theroy of colloidal stability depends on what 2 types of interactions between particles? When is the emulstion stable?

Answer 26

van der Waals and electrostatic repulsion between electrical double layers of identical sign Stable is the repulsion potential > attraction potential

Question 27

Are emulstions thermodynamically and kinetically stable systems?

Answer 27

No

Question 28

What are the 3 steps to the destabalisation process of emulsions?

Answer 28

Flocculation Coalescence Creaming

Question 29

How can we assess the stability of an emulsion?

Answer 29

Gravitational separation. Large droplets cream faster. (shake and wait) Droplet profiling. (while blending, infrared beam directed through sample) % scattered light-> size of droplets. Microscopy (measure average size of air pockets, density etc) Rheology/shear stress (measure viscosity how product is disrupted by stress)