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What is used as a standard referene protein?
Egg albumin is used as a standard reference protein (its PER is high and it has a well balanced amino acid composition)
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What is the main difference between the yolk and the white of an egg?
The yolk is high in lipid content
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What is the egg white?
It is a complex colloidal solution containing avariety of distinct proteins
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What is ovalbumin?
It is a globular phosphoglycoprotein with a molecular weight of about 45,000 daltons
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What protein is responsible for meringue foam?
Ovalbumin
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How is ovalbumin denatured?
Readily denatured by surface forces, but not by heat
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What is conalbumin?
Very heat sensitive protein which is largely responsible for egg white heat coagulation- denaturation sensitivity can be reduced by the addition of Al3+ ions- important for pasteurization of liquid egg
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What is ovomucoid?
A glycoprotein (0.8% hexose and 1.4% hexoseamine) with trypsin inhibiting properties
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What happens if ovomucoid is not denatured?
Capable of interfering with the proteolytic enzyme trypsin if not denatured and reduces the nutritional value of the proteins- considered a protective mechanism for the egg
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What is lysozyme?
Low molecular weight basic protein (~12,000 Daltons) which is capable of hydrolyzeing (lysing) the cel walls of bacteria- consiered a bacterial defense mechanism aainst organisms that penetrate the egg shell (it is prous)
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What is ovomucin?
Polydisperse glycoprotein- very large macromolecule, with a molecular weight in excess of 7 million daltons
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What property is ovomucin responsible for?
- Responsible for the mucoid-like high viscosity of egg white
- Contributes extensively to the gelatinous structure of the egg white- contains up to 30% carbohydrate
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How are the functional properties of egg white impaired?
Most functional properties of egg white are impaired if egg white is denatured to any extent during pasteurization or other heat procesing operations
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What is the general composition of egg yolk?
Very complex system, composed mainly of lipoproteins (16% lipid, 36% protein, 48% H2O)
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How is egg yolk split into two major fractions?
High speed centrifugation into a higher density aqueous plasma fraction and a lower density lipidic granular fraction
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What does the plasma fraction of egg yolk contain?
The plasma fraction contains mainly globular proteins collectively termed livetin
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What is the granular fraction of egg yolk composed of?
Granular fraction is mainly composed of lipoproteins which have a fair amount of phosphorous associated with it- termed phosvitin
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What is the unique cereal protein from wheat?
Gluten
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How is gluten isolated?
As a byproduct of wheat starch manufacture
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What is gluten used to produce?
Gluten is used to produce protein hydrolysates and is used as an additive to strengthen soft wheat flours
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What is wheat flour?
Wheat flour per se is the ground endosperm of the wheat kernel made up of starch granules held within a protein matrix
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Why is gluten unique?
It is capable of providing loaf volume, a property which makes bread and other wheat based leavened products so palatable
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What is gluten made up of?
Gluten is made up of glutenin and gliadin
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What is glutenin?
Glutenin is a Glutelin- protein soluble in dilute alkali or acid- consisdte of a hetergeneous group of proteins which are cross linked by intermolecular disulphide bonds
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What happens if glutenin is isolated and hydrated?
It forms a very tough elastic mass, somewhat like chewing gum
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What is gliadin?
- Gliadin is a hydrophobic prolamine (requires alcohol for solubilization)
- Consits fo a hetergeneous group of proteins which are not cross linked, but contain extensive intramolecular disulphide bonds and free SH groups
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What happens if gliadin is isolated and hydrated?
If isolated and hydrated gliadin will form a very viscous solution
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What is formed when glutenin and gliadin are mixed?
When glutenin and gliadin are mixed together, a viscoelastic mass (dough) is formed
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What is the unique viscoelasticity due to?
The uniue viscoelasticity is due to the interaction of glutenin and gliadin, via the reaction of their sulfur S-S and S-H groups
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What happens when you mix flour with water?
- When mixing flour with water, sulfhydryl-disulfide interhange takes place via the reaction of free SH groups with S-S goups to crosslink and polymerize the proteins
- These bonds are broken and reformed to produce a cohesive viscoelastic mass called dough
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Why do we incorporate yeast in dough?
We incorporate yeast to produce CO2 by fermentation to make it rise
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What is a summary of reactions that happen in a bread loaf?
With heat the dough expands, starch gelatinizes, proteins denature and the product sets- results in a desirable expanded, light product
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Who has a problem with gluten?
Celiac patients
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Which plant seeds have high protein contents?
Legumes and oilseeds
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What is most of the protein from oilseed crops in north america used for?
Animal Feed
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Why is soy protein better than animal protein?
It is cheaper and more effecient to produce plant protein than animal protein
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What is left after expelling and solvent extraction and desolventization of soy protein?
High protein press cake
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What is soy grits?
When high protein press cake is grount to 100-200 mesh
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When is soy flour?
When high protein press cake is ground to <200 mesh
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What isd soy grits and soy flour made of?
About 40-50% protein as well as sunstantial amounts of carbohydrate and some ash
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What is the carbohydrate portion of soy protein made of?
Carbohydrate portion consists of ~equal portions of polysaccharides and oligosaccharides (predominantly raddinose and stachyose)
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What are the oligosaccharides in many bean species resposible for?
Flatulence
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How does one overcome the side effect of flatulence in soy products?
This is generally done by producing a soybean concentrate, in which the oligosaccharides have been removed along with a substantial portion of the ash
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What does soybean concentrate contain?
Soybean concentrate contains both polysaccharides and protein, but the oligosaccharides and much of the ash has been removed
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What is protein isolate?
A more concentrate protein isolate can also be produced using an alternative process by removing all the carbohydrate
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What are soy proteins high in?
Soy proteins are high in lysine and are a good supplement for cereals which are low in this amino acid
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What is the limiting amino acid in soy protein?
Methionine
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What is the isoelectric point of soy proteins?
Soy proteins are mostly globulins, soluble in dilute salt solutions and hae an isoelectric point close to a pH of 4.5
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