protein found in the viscous or thicker albumen layer
highly phosphorylated glycoprotein so referred to as a phosphoglycoprotein
readily coagulated or denatured by heat, so participates in heat induced gelation/coagulation of egg proteins
what is ovotransferin?
this protein binds and transfers Fe
what does bacteriostatic mean?
acts to prevent bacterial reproduction by stopping DNA replication
what does bactericidal mean?
acts to kill bacteria by disrupting the cell membrane
what is ovomucoid?
much smaller glycoprotein, about half the size of ovalbumin
less viscous than ovalbumin and is found in the thin layer albumen
has heat resistance and foaming properties and accounts for the ability of egg white to form foams
which protein is responsible for the ability for egg white to form foams?
what are the major carbohydrates found associated with ovomucoid?
what does lysozyme do?
proteolytic enzyme that acts to disrupt cell walls and thereby prevent microbial contamination
what is ovomucin?
large molecular weight glycoprotein, comparable in size to ovalbumin
thus it is also viscous and found in the thick layer or more viscous albumen layer
what do flavoproteins do?
bind riboflavin and participate in the electron transport chain
what is ovoinhibitor?
a broad spectrum serine protease inhibitor
what does avidin do?
can bind strongly to biotin and prevent it from transporting CO2 units
how many and which type of proteins are found in the albumen?
~0.03% phospholipids, triglycerides, and cholesterol
what are chalazae?
cord-like proteinaceous material that transfers the albumen layer from the egg shell membrane to the egg yolk membrane
the chalazae act to hold the egg yolk in its place within the egg structure and prevent it from moving around
what is it estimated that 2 eggs a day can provide?
20% of daily protein requirements (65-80g/day)
all essential amino acids
all essential FAs and high PUFA content, particularly α-linolenic acid
all known vitamins except C
very high in vitamin D
what percentage of the whole egg is egg white?
what kind of emulsion is an egg yolk?
what percentage of the total egg is the yolk?
what is the total solids content of an egg yolk?
what is the egg yolk surrounded by?
a membrane known as vitellin
where does the color range of an egg yolk come from?
depends on carotenoid content, usually from the animal's diet
what is the composition of an egg yolk?
mostly moisture, then 32% lipids, 16% protein
carb, vitamin, and mineral content is negligible
which proteins are present in the egg yolk?
2 types of lipoproteins (HDLP and LDLP)
lipid-free globular proteins
what is the density of LDLP?
density lower than that of water (~.98)
what are the major components of LDLP?
triglycerides (TGA), phospholipids (PL), and cholesterol
what is the density of HDLP?
greater than water, so >1
what are the major components of HDLP?
phospholipids (PL), triglycerides (TGA), with some amount of phosphates
what are livetins?
lipid-free globular proteins
fat free, devoid of phosphate groups
highly ionic and water soluble
they are the egg yolk equivalent of blood proteins in terms of function
what are phostivins?
phosphoproteins in the egg yolk
what are the amino acids present in the phosphoproteins?
predominantly serine residues (~50%)
and 90% of those are esterified with phosphate groups
what are the phospholipids found in egg yolk?
phosphotidyl choline (leuithin)
phosphotidyl ethanol amine (cephalin)
lysophosphotidyl ethanol amine
what is responsible for the emulsifying capacity of phospholipids?
they are amphiphilic, with both polar and non-polar sides
what are the types of triglycerides present in egg yolk?
SFA (saturated fatty acids)
which are the most common saturated fatty acids in egg yolk?
palmitic acid and stearic acid
what is the proportion of SFA in egg yolk?
fairly constant between 30-35%
what is the major MUFA in egg yolk?
what is the MUFA content in egg yolk?
ranges between 40-45%
what is the major PUFA in egg yolk?
what is the PUFA content in egg yolk?
what is the cholesterol content in an egg yolk?
ranges from about 1-2mg per 1g of egg yolk
which percentage of egg yolk cholesterol is in the esterified form, with the balance being in the free form?
about 15-16% is in the esterified form
what is the average diameter of an LDLP micelle?
which is the most highly phosphorylated protein known to date?
where is 95% of the iron in eggs found?
in the yolk
lipids constitute what percentage of total egg yolk solids?
how are the fatty acids of eggs derived?
synthesized through de novo lipogenesis
incorporation of dietary lipids
what are some deteriorative changes that occur in dried whole egg and egg yolk?
due to Maillard reaction (between cephalin and glucose) leads to discoloration and loss of palatability
why remove glucose prior to egg drying?
curtails the development of off-flavor during storage
how is desugaring of eggs done?
glucose is removed from egg or egg yolk through addition of glucose oxidase and catalase
what are designer eggs and what are some examples?
manipulating the diets fed to birds
omega-3 eggs are an example (can reach up to 500-600mg/egg, causes a darker yellow color to the yolk)
other examples include vitamin A and E enriched eggs
studies are going on to increase the content of what in eggs?
essential minerals such as selenium, iodine, chromium through supplementation of hen feed
what is the major pathogen of concern in eggs?
Salmonella enteritidis (SE)
how does SE contaminate eggs?
from the outside of the shell following contamination in the oviduct or from the feces
may enter the egg in the oviduct prior to the laying down of the egg shell, although there is limited evidence for this route of contamination
what is an effective safeguard against SE contamination?
maintenance of eggs at refrigeration temperatures throughout processing
*TRUE OR FALSE: egg shell is primarily calcium apatite.
*describe in detail the compositions of egg yolk lipids
FA composition in egg yolk is typically 30-35% SFA, 40-45% MUFA, 20-25% PUFA
the amount of SFA, primarily palmitic (16:0) and stearic (18:0), is fairly uniform and changes little with changes in the dietary fats
in contrast, linoleic acid content increases and oleic acid decreases when the level of dietary PUFA is elevated (this aspect is of particular interest for the improvement of the nutritional value of egg yolk)
*TRUE OR FALSE: storage lipids in muscle are primarily fatty acid triesters of glycerol and the most prevalent fatty acid is oleic acid.