P7. Eggs, Soy and Cereals Flashcards
what is another name for egg white?
- __% water
- __-___% protein, depending on what?
- __% lipid
- __% carbs (2 types ish)
- albumen
- 88% water
- 9.7-10.6% depending on age of hen
- 0.03% lipid
- can reach almost 1% –> either free (almost glucose) or combined with protein (glycoproteins)
4 major egg-white proteins
- but egg white proteins –> more then ___ individual constituents
- ovalbumin
- ovotransferrin
- ovomucoid
- lysozyme
- more than 40 individual constituents
most abundant protein in albumen?
- ___% total egg-white protein
- what type of protein is it? –> shape protein?
- MW? how many aa?
- only egg-white protein to contain what?
- ovalbumin
- 54% total of egg-whites
- phosphoglycoprotein –> globular protein
- 44.5 kDa, 385 aa
- free sulfhydryl groups
ovalbumin readily _______, process which is observed when egg white sets on _________. Forms a transparent __A__ or a ________ ___A___ depending on (2) of the solution
- coagulates
- heating
- transparent or turbid gel
- depending on ionic strength and pH
ovalbumin also easily denatured when exposed to a ____ _______ and is important in conferring stability to ______ (dispersion of what in what?)
- new surface
- foams (gas in liquid)
ovotransferrin (also known as what?)
- accounts for __% of egg white protein
- MW of ?
- belongs to the _______ family –> what does it do?
responsible for what?
- conalbumin
- 12%
- 77-80 kDa
- transferrin family –> group of iron-binding proteins widely distributed in various biological fluids. Iron-sequestering properties are responsible for bacteriostatic and bactericidal activities
which protein is the most easily heat-denatured egg protein? but is less susceptible to surface denaturation than ?
- ovotransferrin
- less susceptible to surface denaturation than ovalbumin
which egg-white protein is also present as component of egg-yolk proteins? bit different though?
ovotransferrin! only differing by its carbohydrate prosthetic group
ovomucoid is a __________ consisting of __ tandem homologous domains, each cross-linked by # ________ bonds, with a total molecular weight ___ kDa
- _____ aa
- ___% carbohydrates (present as what? attached to polypeptide through what residue?)
- glycoprotein
- 3 tandem domains
- cross-linked by 3 disulfide bonds
- 28 kDa
- 185 aa
- 20-25% carbohydrates
- present as 3 polysaccharide chains, each attached to polypeptide through asparaginyl residue
lysozyme
- __% of egg-white protein
- ___ aa
- how many disulfide bridges?
- 3.4% egg-white protein
- 129 aa
- 4 disulfide bridges
lysozyme is a _________ enzyme commonly found in nature: catalyzes what of the _________ linkage between (2) present in _________ of certain ________ ______ ______
- bacteriolytic enzyme
- hydrolysis of the glycosidic linkage between N-acetylmuraminic acid and N-acetylglucosamine present in polysaccharides of certain bacterial cell walls –> causes rupture of cell wall
lysozyme is used as a natural _____ ______ and is extracted on an _________ scale by combination of (2) tehcniques
- food preservative
- industrial scale
- chromatography and salting-out precipitation techniques
4 properties of lysozyme that make is an important food preservative
- heat-stable protein
- exhibits enzymativ activity over a broad range of temps (from 1°C to nearly 100°C) and withstands boiling water for 1-2 min without loss of activity
- stable in freeze-drying and thermal drying processed + maintains its activity when redissolved in water
- optimum activity at pH 5.3-6.4 (typical for low acid foods)
chemical composition of egg yolk:
% water
% protein
% fat
- 48.7% water
- 16.4% protein
- 32.9% fat
when used in foods, yolk essentially behaves as a ______ but one which is ________ or readily ________ in ________ and which has the ability to ______ other materials
- as a lipid
- soluble or readily dispersed in water
- ability to emulsify other materials
yolk’s ability to disperse in water due to (3 ish)
- high lipid content (63% of solids)
- high proportion of phospholipids (31% of total lipid)
- the fact that 90% of lipids present in egg yolk are associated with proteins to form lipoproteins
4 classes of proteins found in yolk?
- lipoprotein –> separated by ultracentrifugation into low-density lipoproteins (LDLP 68%) and high-density lipoproteins (HDLP 14%)
- lipid-free globular proteins (livetins): 10%
- phosphoproteins: 4%
- minor proteins including enzymes: 2%
LDLP fraction (__________ fraction)
- density of ?
- accounts for ____ of the yolk
- contains __-__% lipid –> lipid composition? (3)
- lipovitellenin fraction
- 0.98
- 1/3 of yolk
- 80-90% of lipid
1. 69% TG
2. 26% phospholipids
3. 5% cholesterol
LDLP primarily present in form of ___A____? suspended in the what?
- describe ____A____ (3 charac. ish)
A: tiny micelles suspended in plasma fraction
- micelles have a core of TG with phospholipids and proteins radiating toward surface of micelle and interacting with water, thereby making a very stable oil in water emulsion
(phospholipids also on outside + cholesterol embedded in phospholipids)
HDLP fraction (_______ fraction)
- density of ???
- makes up what?
- lipovitellin fraction
- density >1
- makes up the insoluble granules
lipovitellin is a ___________ that contains about ___% lipids (ratio btw phospholipids and TG) and small amount of phosphorus (__%)
lipoprotein
- 20% lipid –> 3:2 ratio btw phospholipid and TG)
- <0.5%
what lipid free protein is strongly associated with lipovitellin? in the HDLP fraction
phosvitin! a phosphorus-rich, lipid free protein
livetins:
- _____-free globular glycoproteins
- represent about __% egg-yolk total solids
- soluble in _______
- corresponds to ______ ______ proteins of the chicken
- lipid free globular glycoproteins
- 10%
- water
- blood serum proteins of chicken
________ is a phosphoproteins which makes up ___% of total yolk protein
- most highly __________ed protein known to date
- almost ____% of its aa are _____, of which __% are _________ed
phosvitin
- 10%
- phosphorylated
- 50% are serine
- 90% are phosphorylated
phosvitin has a high/low isoelectric point bc not/very charged
low bc very charged
phosvitin:
- at neutral pH, highly _______ charged owing to ionization of ________ groups = has a strong/weak affinity for ______ ions (particularly ______ ions), such that ___% of _____ in eggs is present in yolk
- negatively charged –> ionization of phosphate groups
- has a strong affinity for metal ions (ferric ions) –> 95% of iron in eggs is present in yolk
though soluble in _____ salt solutions and to some extent in ______, phosvitin is associated with ______ due to strong/weak ionic bonding to __________ proteins and is not found in the ______ fraction of egg yolk
- weak
- water
- associated with granules due to strong ionic bonding to lipovitellin proteins
- not found in the plasma fraction of the egg yolk
what does heat coagulation designate?
designate the process of thermal denaturation and aggregation of proteins in albumen and in yolk
denaturation of protein involves (3)
- breaking of H-bonds
- uncoiling of polypeptide chains
- exposure of reactive groups
denatured proteins interact through _______ and _______ bonds to form protein _________ that may participate in formation of what?
- chemical and physical bonds
- protein aggregates
- formation of 3-D gel network
aggregation of denature albumen proteins occurs by formation of what 3 interactions
- hydrophobic interactions
- electrostatic interactions
- disulfide linkages
in a mixture of all egg-white proteins, aggregation occurs at 2 distinct coagulation temp ranges: ? and ?
- which protein (ovalbumin, ovomucoid, ovotransferrin) denatures at what temp?
- 61.6-62.5°C and 71.0-73.0°C
- Ovalbumin: 84°C
- ovomucoid: 77°C (omelet firms up)
- ovotransferrin: 60°C (runny, soft)
when egg yolk, egg white (albumen) or egg _______ (mixed whole egg) is heated, their ________ change owing to heat induced _________
- egg magma (mixed whole egg)
- properties change (from protein interactions)
- heat induced coagulation
why are egg whites preferred over egg yolk and mixed whole egg as a gelling agent? (2)
- egg white only contains trace amounts of lipids and therefore has good oxidative stability
- egg white is colorless and has a milk flavor, unlike egg yolk or whole egg
heating albumen increase its (2) –> as the temp increases, a __A___ forms
- strength of ___A_____ increases as (2) increases
- viscosity and opacity
- gel forms
- strength of gel increases as temp and heat time increase
- at the isoelectric point, the net charge is _____ and aggregation is unfavored/favored, resulting in gels that are (4)
- as the net charge increases by lowering/raising the pH, protein denaturation is disfavored/favored over aggregation and the resulting gels are (4)
- zero –> aggregation is favored
- gels that are curdy, opaque, low in cohesiveness and lacking a continuous protein matrix
VS - net charge increases by raising the pH, protein denaturation is favored over aggregation
- gels are translucent, quite elastic or rubbery with an extensively crosslinked 3-D matrix
quality of egg white gels is greatly affected by ____ and _______ _______, as is the case for most _______ proteins
- pH and ionic strength
- globular proteins
when egg white is added to food systems, its pH is increased/lowered and egg white functions much more/less effectively in gelling
- pH is lowered
- less effectively in gelling
gel strength and cohesiveness are maximal/minimal at pH values close to the isoelectric point where net charge is maximal/minimal
ie: in the range of pH __-__ in egg white
- minimal at pH close to isoelectric point
- net charge is minmal
- pH 6-7 for egg white
which protein has long served as model to study process of denaturation in heat-induced gels? why?
- egg white ovalbumin
- bc ovalbumin makes up more than half of the albumen protein content –> its behavior dominantly affects the formation of a gel
what (3) influence heat-induced ovalbumin gels?
- protein concentration
- pH
- ionic strength
at pH values far from pI and at low ionic strength, what type of aggregates are formed?
VS
at high ionic strength or at pH values near pI, proteins aggregate to form what? –> what color depending on what?
- linear aggregates are formed (in solution ish)
VS - turbid gel composed of random aggregates –> mixed gel or linear and random aggregates have either a translucent or opaque appearance depending on the relative amounts of linear and random aggregates
with decreasing electrostatic repulsion, 3D networks form what?
a transparent gel
transparent and opaque/translucent gels exhibit higher (2)
- gel strength
- water holding capacity
soybeans:
through plant _______, possible to obtain __-___% proteins and __-__% lipids
- note: for use in biofuel generation, the ratios as _________
- plant breeding
- 40-45% protein
- 18-20% lipid
- ratios are reversed for biofuel
soybean:
- usually an increase of 1% in protein content is accompanied by a decrease/increase of ___% in oil
- this negative/positive correlation is one of reasons for what?
- decrease of 0.5% oil
- negative correlation is one of reasons for lack of interest in high-protein varieties, since production of these varieties does not result in increased income per hectare cultivated
soybean has a low/high protein digestibility corrected aa score nutritionally equivalent to (2) for human growth and health
- high PDCAAS
- equivalent to meat and eggs
main content of protein in soy is found where? which are subcellular structures with diameter of __ to ___ um.
- found in storage sites called protein bodies or aleuronic grains
- 2-20 um
soybean:
- protein bodies are close to ___% protein
- globular reserve proteins make up about ___% of the soy seed protein
- remaining __% is constituted of what?
- 75% protein
- 80% of the 75%
- 20% constituted by biologically active proteins like enzymes, enzyme inhibitor and lectins
name of extracted protein from soybean storage proteins?
glycinin
as in all legumes, bulk of soybean proteins are _________, characterized by their solubility in _____ solutions
globulins
- salt solutions
solubility of soybean proteins in water is strongly affected by ___
- close to ___% of the protein in raw seeds or unheated meal can be extracted at _____ or _______ pH
- as the acidity increases/decreases, solubility increases/decreases rapidly –> minimum is observed at pH ____-____ –> this is the _________ region of soybean proteins
- pH
- 80% of protein can be extracted at neutral or alkaline pH (>7)
- as acidity increases, solubility decreases rapidly
- minimum = 4.2-4.6 –> isoelectric region
what is used to manufacture isolated soybean protein (SPI)? how?
- more precise and detailed fractionation of proteins can be carried out by 3 techniques
pH dependence of solublity
- deffated, unheated meal is extracted with water at neutral or slightly alkaline pH
- protein is then precipitated from the filtered extract by acidification to the isoelectric region –> almost becomes as valuable as whey protein
- ultracentrifucation, gel filtration, electrophoresis
customary to characterize soybean proteins fractions by their _______ _______
sedimentation constants
ultracentridugation of soybean protein at pH ____ and _____ ionic strength produces fractions designated (4) on the basis of their sedimentation constants in _____ at 20°C
- S = _________ unit
- 7.6
- 0.5 ionic strength
- 2S, 7S, 11S and 5S
- in water
- S = Svedberg unit
which 2 fractions constitute about 70% of total protein in soybeans?
- ratio between the 2?
11S and 7S
- 11S/7S ratio may vary from 0.5 to 3
Compare:
- 2S fraction: contains (3)? MW?
- 7S: highly ___________ –> principal component is what?, MW?, also contains (3)
- 11S: what? MW? how many subunits?
- 15S: what?
- 2S: a-conglycinin and low-molecular-weight popypaptides (8-20 kDa) which comprises soybean trypsin inhibitors
- 7S: highly heterogeneous, principal component is b-conglycinin, a sugar containing globulin with MW in order of 150 kDa + also contains y-conglycinin, enzymes (b-amylase and lipoxygenase) and hemagglutinins
- 11S: glycinin = principal protein of soybeans with MW of 320-350 kDa + built of 12 subunits
- 15S: probably a dimer of glycinin (11S)
amino acid composition of soy protein
- exceptionally rich in ________ and can serve as a supplement to ______ foods where this aa is a limiting factor
- which 2 aa are limiting?
- rich in lysine –> supplement to cereal foods and toasted bread
- methionine and cystine –> contain sulfur
soybean, like all seeds, contain enzyme systems necessary for ___________
germination
technologically, most important enzyme in soybean is what?
- role?
- responsible for what? leads to what?
- lipoxygenase
- catalyzes oxidation of polyunsaturated FA by molecular oxygen
- enzyme responsible for rancidity in soybean oil by oxidation of linoleic acid, the major constituent of soybean oil –> leads to beany smell and flavor
which enzyme is frequently mentioned in connection to soy protein products?
- serves as what?
- urease
- serves as an indicator for adequacy of heat treatment given by soybean meal
(put urea: if degraded, means that there’s urease so probs lipoxygenase too)
which proteins in soybean have been found to exert specific physiological effects/________________ factors? (2)
- antinutritional factors
- typsin inhibitors (2S)
- hemagglutinins (lectins)
what are the 2 types of trypsin inhibitors? + MW?
- Kunitz inhibitor –> 20 kDa
- Bowman-Birk inhibitor –> much smaller polypeptide
(interestingly, both trypsin inhibitors (inhibit proteases from working) are protein based)
which type of soybean (2) will impair growth when fed to young rats and chicks?
- effect completely eliminated when soybean component is properly _______?
- raw soybeans OR unheated soybean meal
- properly heated
since ________ __________ are also heat labile, it was concluded that their presence in the diet is responsible for the suppression of ___A_____
- ______A______ is retarded if inhibitors are added to diets containing heat-treated soybean meal
- trypsin inhibitors
- growth
- growth
explain harmful effect of trypsin inhibitors
- hypothesis –> abandoned?
- new theory ish
- inhibition of trypsin in the digestive tract might impair protein digestibility and utilization –> hypothesis was abandoned when trypsin inhibitor did impair growth when fed with diets containing completely pre-digested proteins
- observed that ingestion of trypsin inhibitors can result in increased secretion of pancreatic enzymes into digestive tract
are soybean trypsin inhibitors toxic to humans?
- no direct evidence
- but became customary to make necessary precautions to remove or inactivate trypsin inhibitors from soybean products intended for human consumption
lectins, formally known as _________, are proteins that possess ability to what?
- widely distributed in ______, and some, such as ______ ______ lectin _______, are highly toxic
- hemagglutinins
- ability to agglutinate red blood cells
- in plants –> castor bean lectin ricin are highly toxic
do lectin found in raw soybeans have a bad dietary effect?
- easily inactivated by what?
- no! no observable dietary effect, good or bad
- by heat
what are the functional properties of soybean proteins? (6)
- thicken (viscosity)
- emulsify
- form gels/foams
- produce films
- absorb water and/or fat
- create meat-like texturized structures
soybean protein products constitute important tools in the formulation of so-called what?
fabricated foods
- soybean oil: obtained by what?
- soy meal: what? used for what?
- soy flour: what?
- soybean oil: obtained by solvent (hexane) extraction
- soy meal: grounded flakes after oil extraction, used for feed (cattle, swine, poultry and fish)
- soy flour: defatted soybeans where special care was taken during solvent removal in order to minimize denaturation of the protein (minimum 50% protein content)
what is the starting material for protein enriched soy products?
soy flours
Soy protein concentrate
- __-__% protein content
- manufactured by using what to remove what from what
- resulting in protein with low/high solubility that is incapable/capable of forming a gel or emulsifying fat
- 65-85% protein content
- alcohol to remove the soluble carbohydrates from de-oiled soy flakes
- resulting in protein with low solubility that is incapable of forming a gel or emulsifying fat
traditional alcohol-washed soy protein concentrates are used for protein _________ of foods as well as in production of __________ soy concentrates
VS
- functional soy concentrates are produced by using ____-wash process and an acid/basic pH to remove the _______ _______, followed by neutralization
- fortification of foods
- textured soy concentrates
VS - water-wash process + acid pH to remove soluble sugars
functional soy concentrates do (3 things)
- widely used in _____ industry and also efficient for what?
- hold water + emulsify fat + form a gel upon heating
- widely used in meat industry and also efficient for stabilization of high-fat soups and sauces
soy protein isolate:
- ___% protein content
- _______ in flavor
- ______ in color
- have functional properties: (5)
- > 85% protein content
- bland in flavor
- light in color
1. gelation
2. emulsification
3. water-holding capacity
4. foaming
5. whipping ability
4 types of cereals?
- all contain starch as their ______ component + __-___% protein
- wheat, corn, barley, riche
- major component + 6-20% protein
wheat proteins are functionally of interest in relation to what product?
- unique property of providing _____ ______ makes (2) products more palatable
to baked goods
- loaf volume makes bread and other wheat-based leavened products palatable
what is interesting about cereal proteins?
- which cereal in particular?
- their properties! not their amount of protein
- only wheat protein has leavening property –> other cereal proteins don’t have this property and cannot attain desirable texture of wheat-based products (ie. corn bread)
wheat flour is the _______ _______ of the wheat kernel made up of _______ _______ held within a _______ ________
- ground endosperm
- made up of starch granules
- protein matrix
wheat proteins are often isolated as a by product of _______ manufacture.
- protein fraction is called ________ and is used as an additive to _________ soft wheats
- starch manufacture
- gluten
- strengthen
wheat gluten contains 2 types of protein?
- both contain ______ in the form of (2)
- glutenin and gliadin
- both contain sulfur in form of cysteine and cystine
glutenin
- soluble in dilute ______ or ______
- consists of a hetero/homogeneous group of proteins that are crosslinked by intra/intermolecular ________ bonds
- when hydrated, form a very soft/tough elastic mass
- alkali or acid
- heterogenous group –> intermolecular disulfide bonds
- form a very tough elastic mass like chewing gum
gliadin:
- hydrophilic/phobic ________ (type of aa) –> requires _______ for solubilization
- consists of hetero/homogeneous group fo proteins that are _____ crosslinked but contain extensive intra/intermolecular ________ bonds and free ____ groups
- if isolated and hydrated, forms a very _____ solution
- hydrophobic prolamine –> alcohol
- heterogeneous group –> NOT crosslinked but contain extensive intramolecular disulfide bonds and free SH groups
- very viscous solution
when glutenin and gliadin are mixed together, a ____A____ mass is formed
- viscoelastic mass (dough)
what causes unique viscoelasticity of interaction of glutenin and gliadin? explain interchange
interaction of glutenin and gliadin via the reaction of their S-S and S-H groups
- sulfhydryl interchange takes place via reaction of free SH groups with S-S groups to polymerize the proteins
- kneading the dough breaks the individual disulfide bonds and reforms them (glutenin and gliadin) to produce a cohesive viscoelastic mass
viscoelastic mass is capable of trapping ____ released by ________ ______ (2 ex), thereby _______ and providing increased (______ _______)(A)
- with heat/baking, ____A____ _________, starch ________, proteins _______ and products ______
- CO2
- leavening agents (yeast, baking powder)
- expanding and providing increased loaf volume
- with heat/baking, loaf volume expands, starch gelatinizes, proteins denature and product sets
are pea and bean proteins well balanced nutritionally?
- functional/cost edge compared to soy protein?
- relatively well balanced
- need some functional or cost edge to compete with soy proteins –> not many properties
pea protein concentrates and isolates used successfully as what? (2 ish)
- hamburger and sausage formulation
- high-protein extruded snacks
(use it as a filler)
what are single cell proteins? include (3)
- major problem?
- good functional properties?
- limitation?
- microbial sources of proteins –> bacteria, yeasts, molds
- major problem = high nucleic acid content –> cannot be handled by our livers in excessive amounts if consumed on substantive scale –> can lead to liver damage and gout
- poor functional properties
- major limitation in industrialized nations, which are not short of protein per se, but looking for cheaper and more versatile forms of functional proteins
food scientists are mainly interested in (3) for proteins
- functional properties of proteins
- nutritional quality
- how they are affected by processing (post isolation)
