lecture 6-part 2 (quiz) Flashcards
define what protien functional properties are
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
How is emuslifcation like foaming?
Basically same thing but replace air with oil
what are emulsions?
Dispersion of two or more immiscible liquids in which one of the liquids is disperised in the other as small droplets
how are emulsions formed?
- by inducing mechanical stress or by the presence of an emulsifier (has hydrophobic and hydrophilic components)
- stabilization by formation of cohesive film over surface of droplet
what are foams? and whats it relation to protiens?
Dispersions of gases in liquids, protiens form stabilized foams by creating films around the gas bubbles
what are the two steps of foaming?
- shake: to denature the protien, expose the hydrophobic region and introduces air. The hydrophobic parts orient themselves around the air,
- Stabilization: the orientation forms a protective lining around the air bubbles to stabilize foam
what are polymeric network gels
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.
Gelatin is an example of polymeric networks, what is special about it
It is made when heated solution is cooled but doesnt need the presence of other reagents or pH. It produces a reversible gel
what are aggregated dispersions? (gel)
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
why do aggregated dispersion gels form irreversiable gels?
because the bonds that form are strong and hard to break
Depending on what will ur gel be different?
depending on condition (heat,pH, salt addition)
what is the definition of protien gellation?
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
Describe heat set gel and cold set gelation
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
Cold set gelation doesnt require heat (T/F)?
FALSE
What is the most common example of heat set gelation ?
soy protiens
why is soy protien used so often?
- highest plant protien quality
- viscosity
- gelation
in one sentance what is viscosity?
it is the resistnce to flow, in simple terms refers to thickeness
how is swelling related to viscosity?
Protiens with swelling capacity have high viscoity at low concentrations
whats the difference ebtween newtonian fluids and non-newtoninan fluids?
newtonian= constant no matter the force or amount if time, like water
non-newtonian= viscosity depends on external forces and stress (ketchup)
What behviour in terms of flow does egg white and casein in milk and yogurt protiens posses?
shear thinning (psueodoplastic)
what behviour in terms of flow does soy protien solutions posses and what is the importance?
non-newtonian shear thinning. This allows for creating the structure and texture for plant based products
Describe swelling
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.
why are protiens soluble in polar solvents?
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
at 50% dissociation what does pH equal?
= to the pKa, which is the equilibrium constant
Protiens can act as an acid/base, what are the 2 equilibrium reactions that can occur and the constants?
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)
when calculating the number of constants what are the guidelines?
- 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
What are the factors that influence emulsification (what are the ideal characteristics for emulsifying?)
- low molecular weight
- balanced amino acid composition (charged, polar and non-polar residues)
- good water solubility
- well developed surface hydrophobicity
- stable confomation
what are the factors that influence foaming (what are the ideal characteriztics for foam forming?
- low molecular weight
- high surface hydrophobicity when unfolded
- good solubility
- small net charge
- easy denaturability
what are the factors that influence gelation (aggregated dispersion gels)
that are affected by Ph, salt (increases), type of protiens, protien concentration.
what are the factors the influence viscosity
- protien size
- protien shape
- charge
- solubility
- swelling capacity
- solute type
- molecular flexibility
- temperature
what are the factors that influence swelling
- Dry protien weight→ the amount of water is proportional to dry protien weight
what are the factors the inlfuence solubility
- number of apolar and polar groups
- polar solvents like water, protiens are very soluble in them
- salt concentrations: more soluble at low salt [], solubility decreases at high salt []
- isoletric point: lowest solubility at the isoletric point, solubility increases as pH is increased/decreased away from pI
How can you use protiens in food poducts in term of viscosity
Protiens absorb water and usally swell resulting in increased viscosity which can be used to get desired textures
What food products use gelation to modify texture and organoleptic properties
yogurt and gelatin
how do you calculate isolectric point from pkas??
add pk1 and pk2 together and then divide by 2
