Technical Challenges (1) Flashcards
what 2 main categories can food ingredients be divided into? what does each consist of?
- macrocomponents: water, protein, CHO, lipids
2. microcomponents: vitamins, colorings, flavorings, preservatives, emulsifiers, etc…
define a food additive
- any chemical substance that is added to food during prep or storage
- either becomes part of the food or affects its characteristics for the purpose of achieving a particular technical effect
- eg: substances used to enhance appearance, texture, keeping qualities of a food
according to the canadian food and drug regulations, what do food additives not include?
- food ingredients such as salt, sugar, starch
- vitamins, minerals, AAs (other than ascorbic acid and dicalcium phosphate)
- spices, seasonings, flavoring
- agricultural chemicals
- vet drugs
- food packaging materials
what should a food additive not be?
should not
- mask faulty manufacturing processes
- conceal damage or spoilage
- be used to deceive the consumer
- be used to obtain desirable results that should be obtained through GMP
how are food processing aids different than food additives?
food processing aids have no regulatory definition/requirements
what are main interactions of ingredients in food systems which occurs?
- among macrocomponents
- between microcomponents
- between micro and macro components
what is the goal of manipulating ingredient interactions?
to enhance desirable attributes of foods while minimizing or eliminating undesirable attributes
what are the thermodynamic similarities of formulated foods due to?
common behavior features of structure forming food macromolecules
interactions between macrocomponents may favor what phenoma? (examples)
- thermodynamic incompatibility
- interbiopolymer complexing
- protective colloids
- bridging
- flocculation
describe functionality
property of a food ingredient that affects utilization, except its nutritional value
what are some examples of functional properties of proteins?
- coagulation
- gelation
- structure formation
- emulsification
- water holding capacity
- foam formation
- fiber formation
- fat absorption
what do the properties of protein (eg. AA composition, ionization state of AA, ionic strength, pH) effect?
- electrostatic interactions b/w charged amino and carboxyl groups
- H bonding b/w OH and carboxyl groups
- hydrophobic interactions b/w two non-polar residues
- covalent disulfide linkages between cysteine residues
how does isoelectric points affect functional properties of proteins?
at IE point, functional properties are mostly at max or min levels
how does pH affect elastic type wheat proteins?
- pH at isoelectric point gives the greatest amount of strength
- pH away from isoelectric point has greatest extensible properties (higher tenderness)
- can use this to influence the ratio of elasticity and extensibility
how can proteins be denatured?
by altering H bonds, hydrophobic interactions and salt linkages
what are 2 types of protein denaturing agents? what are examples of each?
physical (heat, shaking, high pressures, UV light)
chemical (pH, salts, synthetic detergents)
define a gel
continuous 3D, solid like, cross liked network of protein molecules in an aqueous solvent
protein gelation is responsible for what characteristics?
- viscoelasticity and texture
- juiciness
- viscosity
- adhesiveness
- water retention
- stability of emulsions and foams
- stimulation of mouthfeel of lipids
- retention of sugars and flavors
what rheological properties can vary between different gels?
cohesiveness
hardness
stickiness
adhesiveness
what three events occur in protein gelation? describe each step
- denaturation: partial unfolding of proteins with changes in secondary structure by heating or treatment with acid, alkali and urea
- aggregation: polymer-polymer and polymer-solvent interactions are balanced
- crosslinking: provides fluidity, elasticity and flow behavior gels with high strength and stability
what three treatments can cause denaturation of proteins?
acid
alkali
urea
crosslinking provides what during protein gelation?
fluidity
elasticity
flow behavior
the gelling ability of proteins is influenced by what?
- protein concentration
- AA composition
- molecular wt
- hydrophobicity of proteins
the development of the 3D network during gel formation is influenced by what?
- method of protein prep
- processing conditions
- environmental factors (pH and ionic strength)
describe the gels formed at the isoelectric pH of proteins. why is this?
- less hydrated and less firm
- structure of gels will be more aggregated instead of ordered
- translucent or turbid
b/c of lack of repulsive forces
at isoelectric pH of proteins, repulsive forces are ____ (incr/decr) and aggregation/precipitation is (incr/decr)
decreased repulsive forces
increases aggregation and precipitation
define WHC
water holding capacity
ability to hold its own and added water during the formulation and the application of forces, pressing, centrifugation or heating
what interactions are important for the water holding capacity of proteins?
protein-water interactions
WHC plays a major role in what?
formation of some food texture, taste and tenderness
why is understanding the WHC important?
to prevent:
- loss of H2O during cooking or freezing, which may result in a drier and tougher pdt
- evaporation and condensation of water on packaging material
- syneresis
define syneresis
contraction of a gel accompanied by the separating out of liquid
describe swelling capacity
- enlargement of food systems
- first step in the solvation of proteins
- defined as spontaneous uptake of H2O by a protein matrix
what does swelling characteristics not include?
characteristics of:
soy isolate
Na caseinate
whey protein
how does protein ingredients with very high WHC affect other components?
can cause dehydration of other components
how does WHC of proteins affect other formula components?
high WHC proteins can cause dehydration of other components. Thus, this affects the order of dry ingredient incorporation into the formula
how does WHC affect the packaging materials?
WHC can be used to determine kinds of packaging materials needed to maintain required moisture content of the pdt
how can WHC of protein ingredients be predicted?
- from type (imino and aminocarboxyl groups)
2. number of polar groups in protein polypeptide chain
what 3 types of side chains are found in proteins? how many water or AA molecules do each of them bind to?
- non-polar AA side chains (alanine and valine): binds 1 water or AA
- polar side chains: binds 2 or 3 water or AA
- ionic side chains (aspartic acid, glutamic acids and lysine): finds 4 to 7 water or AA
what are methods of determining WHC of protein ingredients?
- standard test improved by the AACC
2. absorption isotherm (shows amount of H2O absorbed by the protein as a function of relative water vapor pressure)
describe the absorption isotherm graph
water content increases fast during Aw = 0 to 0.3 and Aw = 0.8 to 1.0
water content increases slowly during Aw 0.4 to 0.75
”s” shape increase in water content as water activity increases
what are factors influencing WHC?
- protein conc
- pH
- ionic strength
- temp
- presence of other components of foods
- length of heat treatment and storage conditions
what are types of food emulsions?
what are the phases in each? what texture do they have? examples?
- oil in water (o/w):
- water is the continuous phase
- oil is the discontinuous phase
- creamy texture
- eg. reconstituted milks - water in oil (w/o):
- oil is the continuous phase
- water is the discontinuous phase
- greasy texture
- eg. margarines and fatty spreads
how does emulsification affect hydrophobic portions of the protein?
aligns the hydrophobic portions of the protein with the fat so they can interact
how is emulsification and hydrophobicity correlated
positive correlation
higher emulsifying capability = higher hydrophobicity of proteins
what are 3 characteristics used to describe emulsifying properties of proteins?
describe each.
- emulsifying capacity (EC): amount of oil (mL) emulsified under specific conditions by 1g protein
- emulsifying stability (ES): capacity of emulsion droplets to remain dispersed without separation by creaming, coalescing and flocculation
- emulsifying activity index: EA m^2/g
what do emulsifying characteristics of proteins depend on?
- source of proteins
- properties on conditions of emulsification
- conc
- pH
- ionic strength
- viscosity of system
- solubility
what are the types of emulsion instability?
- coalescence
- flocculation
- creaming
- breaking
what is HLB? what is the equation used?
hydrophile lipophile balance
HLB = (wt of hydrophilic) / (wt of total) x 100/5
how is HLB value and protein hydrophobicity related?
[pro hydrophobitiy] = 1- [HLB]
[pro hydrophobicity] = NP residues] / ([NP] + [polar])
how are proper emulsifiers chosen?
choose an emulsifier with the HLB value which matches required HLB value of the oil or lipid to be emulsified
describe the emulsification properties of milk proteins
- good heat stability
- good emulsification properties
- works well in retorted beverages in a neutral pH
describe the emulsification properties of soy proteins
- good emulsion-stabilizing properties
- functional properties are important in comminuted meat pdt
describe the emulsification properties of whey proteins
- favourable for stabilizing emulsions and foams in acid-stable proteins
describe the emulsification properties of gelatin
- able to protect colloids
- inhibit growth of sugar crystals
- prevents formation of hard, gritty texture and a poor mouthfeel
compare using one protein versus combination of proteins
combination of multiple proteins is better to achieve desired properties
define foaming
creation and stabilization of gas bubbles in a liquid
what is essential for the formation of protein-based foams?
- diffusion of protein to the air-water interface to reduce surface tension
- partial unfolding of the protein association which leads to an intermolecular cohesive film
the foaming properties of proteins encompasses what 2 aspects?
- ability to produce a large interfacial area
2. ability to form a tenacious interfacial film that can withstand internal and external forces
what does “overrun” mean
the foaming capacity of the protein
overrun = (vol of foam - vol of initial liquid) / vol of initial liquid x 100
how is foam stability expressed?
the time required for 50^ of the liquid to drain from a foam
or for a 50% reduction in foam volume
what are hydrophobins?
- a unique class of proteins produced by filamentous fungi
- has good interfacial and foam stabilizing properties
what is an example of how viscosity is related to gelation and protein-protein interactions?
modifications of isolated soy proteins produces low to very high viscosity pdts
