Exam 3 Property of Fresh Meats Flashcards
major factors that affect meat freshness
- visual appearance
- flavor
- juiciness
- tenderness
things that affect fresh meat pigments
- myoglobin content (80-95%)
- hemoglobin (from residua; blood)
- cytochromes, catalase (oxidative enzymes)
things with higher myoglobin content
- male more than female
- older more than younger
- red muscle more than white
- physical activity more than
factors affecting meat color
- muscle pH
- rate of pH decline
- uneven chilling
- chemical state of heme iron in myoglobin
chemical state of heme iron in myoglobin is influenced by
- type of packaging (time exposed to air)
- microbial contamination
- age of meat
- cooking
- curing
heme
- located in center of protoporphyrin (organic component) bound with 4 pyrrole rings
- 5th binding site is occupied by a histidine residue
- 6th binding site is available to bind oxygen
DMB
- deoxymyoglobin
- Fe++ (ferrous)
- no O2 present
- purple
- loses oxygen
OMB
- oxymyglobin
- Fe++ (ferrous)
- atmospheric O2
- red
- gains oxygen/ exposed to air so loses binding ability to electrons
MMB
- metmyglobin
- Fe+++ (ferric)
- low O2 present
- brown
- denatured bc loses electrons
- irreversible after adding heat
CO-MB
- carboxymyoglobin
- Fe++ (ferrous)
- CO present
- red
- strong binding component to heme
mitrosomyoglobin
- meat after nitric acid is added
- permanently fixed pink color
- add heat to get nitrosohemocrome
effects of adding vitamin e
- antioxidant so the myoglobin content is protected from denaturation
- myoglobin extends shelf land brighter color
- less retail cuts discounted with vitamin e
ferrous (Fe++) H2O
purple -> deoxymyoglobin
ferrous (Fe++) O2
red -> oxymyoghobin
ferrous (Fe++) NO
unstable pink -> nitric oxide myoglobin
ferrous (Fe++) CO
red -> carboxymyoglobin
ferric (Fe+++) H2O (globin)
brown -> metmyoglobin
ferric (Fe+++) H20 (denatured globin)
brown/gray -> denatured metmyglobin
ferric (Fe+++) SH
green -> sulfmyoglobin
HH2O2 (hydrogen peroxide)
green -> choleglobin
sodium nitrate
smaller % of sodium nitrate coverts to sodium nitrite after eaten (can form nitrosamines)
nitrosamines
- proteins (amines) combined with nitrites
- cancer-causing
veggies contain ______ which is an ______ that helps prevent nitrosamine formation
ascorbic acid / antioxidant
flavor component of fat
- protein/ ATP breakdown products (IMP, hypoxanthine)
- affected by feed, animal age, gender
- lipid oxidation/ rancidity, microbes
flavor component of lean meat
- fat component has to be under 1% to be considered fat free
- meaty flavor
- browning reaction
- amino groups + reducing sugars = melanoidins
fatty acid oxidation
18: 1 (36)
18: 2 (4)
18: 3 (trace)
relative rate of oxidation
1:100:1200:2500
oxidative deterioration of fats
rancid / off odor and off flavor
what factors affect juiciness
- water holding capacity
- lipids (oils) in meat
- cooking
tissue factors affect tenderness
- rigor toughening
- post mortem proteolysis
- connective tissue
- intramuscular fat
factors influencing meat tenderness
- vitamin D feeding
- stress
- muscle location
- fiber size
- carcass (hanging method, aging 7-21 days)
- mechanical (grinding, macerating)
- marinade/ injection (cooking)
proteolysis
- protein degration or breakdown
- causes meat tenderization
calpains
- calcium activated proteases (breakdown proteins)
- high calpastatin = tougher meat
- inhibited by calpastatin
shorter sarcomere
- tougher meat
- actin and myosin squished together
- length .8
what does calpain act or not act on / breakdown
- not act on contractile proteins (actin and myosin)
- not act on stromal proteins (collagen, keratin, elastin)
- act on myofibrilliar, non-contractile proteins (desmin, titan, troponin)
regulators of tenderness
- collagen content and solubility
- sarcomere length
- post mortem proteolysis
marbling effects on tenderness
- very little!
- marbling effects juiciness and flavor not really tenderness
how to cook high collagen products
slow, moist heat (crock pot)
how to cook low collagen products
dry cookery (grill)
