2. Poultry and Eggs Flashcards
what counts as “poultry”?
domesticated birds of commercial value (eg. chicken, turkey, duck, goose)
globally, what are the 1st and 2nd major sources of animal protein?
1st: pork
2nd: poultry
what are some reasons that poultry consumption has become higher than other animal proteins?
- considered healthier than red meats
- less sat fats
- poultry fats are mostly located in the skin and is easy to remove prior to cooking
- cheap production costs
- smaller space requirement
what are the 6 classifications of market forms of poultry meat?
describe each one.
- broilers/fryers: 6-8 weeks old chicken. Wt = 2.5lbs
- capons: neutered male chicken. Wt = 6-8lbs
- cock/rooster: over 10 month old male. Wt = 6-8lbs
- fryers: 6-8 week old. Wt = 2.5-3.5lbs
- roasters: over 8 months. Wt = 3.5-5lbs
- stewing chicken: spent hens over 10 months old. Wt = 5-7lbs
what are classifications of poultry meat based on?
age and wt
what is a spent hen?
what kind of meat do they have?
hens who have stopped producing eggs
very tough meat
what factors does poultry meat composition depend on?
breed diet age sex growth environment
the breed of poultry meat depends on what two factors?
place of origin
physical traits
how is the protein content of poultry similar to that of red meat?
the muscle composition and structure is similar
what are 3 main poultry proteins?
sarcoplasmi
myofibrillar
connective tissue/stroma
describe the differences between the 3 main poultry proteins
the differences are mostly based on solubility
which poultry protein are H2O soluble. What is the importance of this?
sarcoplasmic proteins are H2O soluble
this makes them easy to be removed from the tissue with H2O
what are 2 forms of moisture found in poultry protein?
- tightly bound to protein via H bonds
2. held loosely within compartments in muscle tissue
what is WHC?
water holding capacity
what are conditions that enhance protein denaturation and reduces the WHC?
- cooking
- conditions that promote acid production and pH decline
- frozen storage
- condition that promotes protein oxidation
how do polyphosphates enhance WHC (water holding capacity) in poultry?
- polyphosphates promotes dissociation of actomyosin into actin and myosin
- actomyosin has low WHC, while actin and myosin both have higher WHC
- thus, polyphosphates enables water binding and retention
describe the lipid profile of duck and goose compared to chicken and turkey
duck and goose have:
- higher amounts of lipid since they have more dark meat, which has higher levels of fat per gram than white meat
- higher amounts of monounsat fats
- lower polyunsat fat (thus, more prone to oxidation)
what is the major monounsaturated FA in poultry?
oleic acid (18:1c)
what is the major PUFA in poultry?
linoleic (18:2c) linolenic acid (13:8c) arachidonic acid (20:4c)
is there higher moisture and fat content with the skin on of off of poultry meat?
skin on: higher fat content and lower moisture content
skin off: lower fat content and higher moisture content
what is MDPM?
- mechanically deboned poultry meat
- the meat separated from the carcass skeleton after removal of larger cuts of meat
describe the steps of how MDPM is obtained
- pressure is applied to the carcass or bone attached meat. This causes the soft tissues (protein, fat, skin) to separate from the bones
- pressure chamber has small holes, where the separated materials can pass through while bones are retained inside the barrel
what is the main goal of processing meats
- to increase product variety and convenience
- extend meat shelf life
- facilitate distribution
what are 3 categories of processed meats?
- minimally altered: eg. cured ham, bacon, corned beef
- moderately altered: eg. sectionned and restructure
- extensively altered: comminuted (broken down to small particles) and then re-formed (eg. sausage and luncheon meats
what is curing meat?
treating fresh meat with salt and nitrite/nitrate for the purpose of preservation and obtaining desirable color and flaour
describe the physical characteristics of cured meats
- pinkish color
- distinct aroma
what are the most common curing agents?
nitrite (NO2-) or nitrate (NO3-)
what is the immediate precursor for the actual curing agent?
nitric oxide (NO)
what are the functions of nitrite in curing meats?
- contributes to characteristic flavour of cured meat
- inhibits growth of spoilage and pathogenic microorganisms (especially clostridium botulinum)
- retards development of oxidative rancidity
- develops and stabilized pinkish red color
what are the steps of color development in cured meats?
- nitrate is dissolved in H2O. This forms nitrous acid (HNO2)
- HNO2 decomposes to nitric oxide (NO) under reducing conditions
- NO binds to heme iron in myoglobin to produce nitrosylmyoglobin (MbNO), which is pink. This reaction is reversible, thus, does not give permanent color.
- meat is heated, which converts MbNO to a more stable compound, nitrosylhemochromagen, as a result of globin denaturation
- reducing agents are added to reduce nitrite to nitric oxide and ferric ion of metmyoglobin to ferrous ion
what are 3 types of meat processing?
physical
chemical
thermal
describe deboning, in physical treatments of processing meat.
- involves spinning scraps in perforated drums with H2O under high pressure
- this causes the scraps of meat to separate from bones
- then, can restructure or mince
describe the function of salt in the chemical treatments of processing meat
- reduces H2O activity to control microbial growth and inactivate certain enzymes
- extracts salt soluble proteins
- flavouring
what are examples of antimicrobials used in chemical treatments of processing meat?
nitrates and nitrites, acidifies NaCl, chlorine dioxide, peroxy acidic acid, peroxy octamoic acid
what is NO3-? what is NO2-?
NO3- = nitrate NO2- = nitrite
how is NO3- converted to NO2-?
removal of H2O by Na erthorbate (vitC) or nitrate reductase (an enzyme naturally present in animal tissues) with NADH as the H donor
what compound MbO2 converted to?
is this conversion desirable or not?
MbNO
desirable because it is an antioxidant
what is MbNO?
what is MbO2?
MbNO is nitrosylmyoglobin:
- an antioxidant that protects against oxidation damage to preserve flavour and color
- pink color
- desirable compound
MbO2
- red color
- not desirable
what reaction is the conversion of MbO2 to MbNO coupled with?
NO to O2
what is the most commonly used reducing compound? describe this compound.
sodium erythorbate
- an isomer of ascorbate
- also an antioxidant that stabilizes color and flavor to decrease the formation of nitrosamines
what are some chemicals that improve water holding capacity?
starch
phosphates
texturizers
enzyme inhibitors (eg. potato powder and blood plasma protein)
what are some types of thermal treatments used for meat processing?
- canning
- heat treatment
- cooling treatment
describe the steps of delation of poultry meat
- protein denaturation
- denatured protein aggregates due to hydrophobic interactions
- cross linkages form between the aggregates by using interactions of side chains of the amino acids, which creates a gel
how can poultry meat create emulsions?
what can these emulsions be used for?
by blending fat and protein found in poultry meat, you can get fat globules distributed throughout the aqueous network
can be used for butters or “breading”
what are the main components of the egg shell?
which is the biggest component?
CaCO3 –> biggest component. Makes up 98% of the shell
other components:
MgCO3
Ca3 (PO4)2
organic matter (mainly protein)
what part of the egg shell allows for gas exchange?
pore canals
describe how the pore canals in the egg shell prevent microbial contamination
the pores are filled with protein fibers and sealed by a cuticle layer made of keratin, which is used to prevent microbial contamination
what are ooporphins?
the pigments dispersed on the surface of the shell
can range from dark brown to chalky white
what are other uses of egg shell?
compost, gardening, cosmetics, nail polish, clarifying/fining agent (by binding impurities in beverages to clarify it)
what is the egg’s primary protection against microbial contamination?
the shell membrane
describe the composition and function of the egg shell membrane
- has an inner and outer (thicker) membrane
- made of keratin and collagen
- function: allows exchange of material between aqueous internal and external environments of the egg
why is there an air pocket in the egg?
when the egg is in the animal, the temperature is higher, but when the egg comes out, it is cooler, which causes the internal content to collapse, creating an air pocket
fresher eggs have ____ air pockets
smaller/bigger
smaller
bigger air pockets means the egg is ____ fresh
more/less
less
what are the 2 main constituents of the egg white?
albumen and water
what are the 4 layers of egg white?
two thick
two thin
what are the two thin layers of egg white important for?
the foaming properties of eggs
how does glucose appear in egg white?
as free glucose or combined with proteins as glycoprotein
describe the chemical composition of egg white
protein: ~10%
CHO: ~1%
lipid: ~0.03%
what are the major egg white proteins?
ovalbumin ovotransferrin ovomucoid lysozyme ovomucin
describe ovalbumin
- a phosphoglycoprotein
- readily forms gels
- coagulates and denatures easily, which gives stability to foams
- key function: carrier of fat, which allows it to form a network that traps air to produce foam when egg white is beaten, which increases volume
which major egg white protein allows for increasing volume when egg white is beaten?
ovalbumin
describe ovotransferrin.
what functions does it have? what type of activities does it have?
- function: Fe binding and transfer protein
- has bacteriostatic and bactericidal activities
describe ovomucoid.
- a glycoprotein
- CHO present are glucosamine, mannose, galactose and sialic acid
- resistant to heat coagulation
describe lysozyme
- bacteriostatic
- very stable to heat treatments and freeze-drying
- breaks down glycosidic bonds in cell walls
describe ovomucin
- a large glycoprotein
- function: increases high viscosity to albumen due to large size
- not very heat stable
- heating it enables use as a thickener
describe flavoproteins-apoproteins
- binds riboflavin
- important in ETC
describe ovoinhibitor
a broad spectrum serine protease inhibitor
describe avidin
- a basic protein
- high affinity for biotin
- used in biomedical research
what is chalazae?
- cord like strands continuous with the inner thick white of the albumen
- serves as an anchor to retain the yolk centrally
- normal and wholesome part of the egg (not a contaminant)
what does the color of the egg yolk depend on?
pigments in the chicken feed, since no pigments are synthesized by the chicken
what type of yolk indicates a high quality egg?
a round yolk
what kind of emulsion is egg yolk?
oil in water
it contains lipoprotein and phospholipid molecules suspended in a protein-water matrix
what are the main protein classes in egg yolk?
- lipoproteins
- livetins
- phosvitin
- minor proteins
compare the densities of LDLP vs HDLP
LDLP density < 1.0
HDLP density > 1.0
which lipoprotein does the egg yolk contain more of?
low density lipoproteins (LDLP)
less high density lipoproteins (HDLP)
describe the LDLPs found in egg yolk
- lipovitellenin fraction found in egg yolk
- density <1.0
consists of 3/4 protein of yolk - has high lipid content (consists of TGs, phospholipids, cholesterol)
- primarily present as tiny micelles suspended in plasma fraction.
- micelles have a core of TGs with proteins and phospholipids radiating towards the surface of the micelle and interacting with H2O to form a stable oil/water emulsion
describe the HDLPs found in egg yolk
- lipovitellin fraction found in egg yolk
- density is > 1.0
- makes up insoluble granules
- composition: mainly lipovitellin, which is a lipoprotein with lipid (phospholipid and TG) and small amounts of phosphorus
- lipovitellin can be separated into two components: a and f, based on phosphorus contents
- contains phosvitin (a phorphorus rich and lipid free protein)
what are livetins?
- type of protein class in egg yolk
- lipid free globular glycoproteins
- H2O soluble
- corresponds to blood serum proteins of the chicken
what are phosvitins?
- type of protein class in egg yolk
- most highly phosphorylated protein known to date
- soluble in weak salt solutions
- strongly associated with granules thorough ionic bonding to lipovitellin proteins
- not found in plasma fraction of egg yolk
what are other egg yolk phosphoproteins?
vitellin and vitellenin
both are:
- insoluble in acid and neutral solution
- soluble in alkaline solution
what are the major lipid components in egg yolk?
TGs phospholipids cholesterol FFA minor lipid components (eg. carotenoids)
order the TGs in egg yolk from most to least
MUFA (40-45%)
SFA (30-35%)
PUFAs (20-25%)
which polyunsaturated FAs are mostly present in egg yolk lipids?
linoleic and alpha-linolenic acids
when the level of dietary PUFAs are elevated, what increases and what decreases?
linoleic acid content increases
oleic acid content decreases
which SFAs are mostly present in egg yolk?
palmitic (16:0) and steric (18:0)
what is the major sterol in egg yolk lipid?
cholesterol
what forms can cholesterol be found in egg yolk?
free cholesterol (mostly)
some cholesterol ester
does the size of the egg influence the total cholesterol content?
yes. larger eggs have a higher total cholesterol content
why is egg yolk often used as an emulsifier in food products?
since egg yolk phospholipids are amphiphillic
what are components of phospholipids found in egg yolk?
phosphatidyl choline (lecithin) lysophosphatidyl choline phosphatidyl ethanolamine (cephalin) lysophosphatidyl ethanolamine sphingomyelin inositol phospholipid plasmalogen
which phospholipid component forms a ziwtterionic phospholipid over a wide pH range?
phosphatidyl choline (lecithin)
what are 2 minor lipid components found in egg yolk?
lecithin
carotenoids (vitA)
what two factors influences the FA composition of the yolk?
why?
breed of bird
diet of the bird
because the FAs of eggs are derived from the de novo lipogenesis and incorporation of dietary lipids
what are the functional qualities of eggs?
emulsifier, thickener, binding/coating, foaming agent, heat induced gelation and coagulation
what are some nutritional qualities of eggs?
- high quality protein (has all essential AAs)
- high in PUFAs
- high in minerals
- good source of Fe and P, but not Ca
- high levels of sat FAs and cholesterol
describe deteriorative changes in egg
what is an example of this?
- can occur in dried whole egg and egg yolk derived from the maillard reaction
- eg. cephalin + glucose leads to discoloration of dried whole egg and loss of palatability
how can you prevent deteriorative changes in dried egg?
when glucose is removed before the drying process, this eliminated the development of off-flavor during storage
what are methods for removing glucose from eggs to eliminate deteriorative changes?
what reaction occurs?
adding glucose oxidase and catalase
glucose oxidase converts glucose to gluconic acid and hydrogen perioxide
catalase converts H2O2 to form H2O and 1/2 O2
what are designer eggs developed for?
how are they achieved?
- to enhance the image of eggs as healthy and nutritional
- achieved by manipulating the diet fed to birds
what is the major pathogen of concern to food safety of eggs?
salmonella enteritidis (SE)
what 2 ways can SE contaminate eggs?
- from the outside of the shell following contamination of the oviduct or from the feces
- may enter the gg in the oviduct prior to the laying down of the egg shell
how can you prevent contamination of SE to eggs?
maintenance of eggs at refrigeration temp throughout processing
