lecture 6-part 2 (quiz)

Question 1

define what protien functional properties are

Answer 1

They are physical and chemical properties of protiens that affect the protiens behviour in food systems during preperation, processing, storage and consumption. They not only affect behviours but also contribute to the quality and organoleptic attributes of food systems

Question 2

How is emuslifcation like foaming?

Answer 2

Basically same thing but replace air with oil

Question 3

what are emulsions?

Answer 3

Dispersion of two or more immiscible liquids in which one of the liquids is disperised in the other as small droplets

Question 4

how are emulsions formed?

Answer 4

1. by inducing mechanical stress or by the presence of an emulsifier (has hydrophobic and hydrophilic components)
2. stabilization by formation of cohesive film over surface of droplet

Question 5

what are foams? and whats it relation to protiens?

Answer 5

Dispersions of gases in liquids, protiens form stabilized foams by creating films around the gas bubbles

Question 6

what are the two steps of foaming?

Answer 6

1. shake: to denature the protien, expose the hydrophobic region and introduces air. The hydrophobic parts orient themselves around the air,
2. Stabilization: the orientation forms a protective lining around the air bubbles to stabilize foam

Question 7

what are polymeric network gels

Answer 7

Polymeric network gels are formed by long polymer chains (like polysaccharides or proteins) that cross-link to create a water-trapping, three-dimensional structure, typically stabilized by environmental triggers such as ionic changes or pH shifts.

Question 8

Gelatin is an example of polymeric networks, what is special about it

Answer 8

It is made when heated solution is cooled but doesnt need the presence of other reagents or pH. It produces a reversible gel

Question 9

what are aggregated dispersions? (gel)

Answer 9

They are gels formed by globular protiens The steps are as unfollowed, the protien is heated and unfolded, hydrophobic site is released, intermolecular interactions, small spherical aggregates form and then they combine into linear strands which establish gel network

Question 10

why do aggregated dispersion gels form irreversiable gels?

Answer 10

because the bonds that form are strong and hard to break

Question 11

Depending on what will ur gel be different?

Answer 11

depending on condition (heat,pH, salt addition)

Question 12

what is the definition of protien gellation?

Answer 12

the process by which protiens when in certain conditions form a gel like structure that is formed by a continous 3D network of intermolecular and interchain cross links which trap water

Question 13

Describe heat set gel and cold set gelation

Answer 13

Heat set: protien is heated resulting in unfolding allowing it to form a hydrogel network because of hydrophobic interaction

Cold set: Protien is heated resulting in unfolding then it is cooled and forms a hydrogel due to the addition of salts or by reducing the pH which compensates for the charges

Question 14

Cold set gelation doesnt require heat (T/F)?

Answer 14

FALSE

Question 15

What is the most common example of heat set gelation ?

Answer 15

soy protiens

Question 16

why is soy protien used so often?

Answer 16

1. highest plant protien quality
2. viscosity
3. gelation

Question 17

in one sentance what is viscosity?

Answer 17

it is the resistnce to flow, in simple terms refers to thickeness

Question 18

how is swelling related to viscosity?

Answer 18

Protiens with swelling capacity have high viscoity at low concentrations

Question 19

whats the difference ebtween newtonian fluids and non-newtoninan fluids?

Answer 19

newtonian= constant no matter the force or amount if time, like water

non-newtonian= viscosity depends on external forces and stress (ketchup)

Question 20

What behviour in terms of flow does egg white and casein in milk and yogurt protiens posses?

Answer 20

shear thinning (psueodoplastic)

Question 21

what behviour in terms of flow does soy protien solutions posses and what is the importance?

Answer 21

non-newtonian shear thinning. This allows for creating the structure and texture for plant based products

Question 22

Describe swelling

Answer 22

Swelling is based on the hydration of the insoluble protiens, water that is inserted between the peptide chains results in an increase in volume and other physical characteristics of the protien.

Question 23

why are protiens soluble in polar solvents?

Answer 23

Protiens have many polar and charged groups which interact well with polar solvents. As well the structure of protiens are folded so that their hydrophilic groups are on the outside and the hydrophobic groups are tucked inside. The Polar solvents can stabilize the exposed polar groups, increasing solubility

Question 24

at 50% dissociation what does pH equal?

Answer 24

= to the pKa, which is the equilibrium constant

Question 25

Protiens can act as an acid/base, what are the 2 equilibrium reactions that can occur and the constants?

Answer 25

reaction 1: Positively charged amino group can loose a proton to form a neutral molecule

reaction 2: the nuetral molecule can loose another proton to become negatively charged

Each one of these reactions has an equilibrium contstant (K1, K2)

Question 26

when calculating the number of constants what are the guidelines?

Answer 26

• lways have 2 to start, then for every other group you add 1
• gly and alanine is always just 2 no matter how many glycines or alalnies
• Lys, Asp, glu and his add one extra for each

Question 27

What are the factors that influence emulsification (what are the ideal characteristics for emulsifying?)

Answer 27

1. low molecular weight
2. balanced amino acid composition (charged, polar and non-polar residues)
3. good water solubility
4. well developed surface hydrophobicity
5. stable confomation

Question 28

what are the factors that influence foaming (what are the ideal characteriztics for foam forming?

Answer 28

1. low molecular weight
2. high surface hydrophobicity when unfolded
3. good solubility
4. small net charge
5. easy denaturability

Question 29

what are the factors that influence gelation (aggregated dispersion gels)

Answer 29

that are affected by Ph, salt (increases), type of protiens, protien concentration.

Question 30

what are the factors the influence viscosity

Answer 30

1. protien size
2. protien shape
3. charge
4. solubility
5. swelling capacity
6. solute type
7. molecular flexibility
8. temperature

Question 31

what are the factors that influence swelling

Answer 31

1. Dry protien weight→ the amount of water is proportional to dry protien weight

Question 32

what are the factors the inlfuence solubility

Answer 32

1. number of apolar and polar groups
2. polar solvents like water, protiens are very soluble in them
3. salt concentrations: more soluble at low salt [], solubility decreases at high salt []
4. isoletric point: lowest solubility at the isoletric point, solubility increases as pH is increased/decreased away from pI

Question 33

How can you use protiens in food poducts in term of viscosity

Answer 33

Protiens absorb water and usally swell resulting in increased viscosity which can be used to get desired textures

Question 34

What food products use gelation to modify texture and organoleptic properties

Answer 34

yogurt and gelatin

Question 35

how do you calculate isolectric point from pkas??

Answer 35

add pk1 and pk2 together and then divide by 2