P7. Eggs, Soy and Cereals
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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