meat science exam 3

3 types of muscle proteins

sarcoplasmic (water solble, enzymes, myoglobin, 25-30)

myofibrillar (salt soluble, actin, myosin, 50-60)

stromal (connective tissue 10-20 insolubule requires strong acid/abse collagen elastin)

primary functions in meat animls

movement, support, maintenance of body temperature, dietary protein source

marbling meat s in what part of muscle

IM fat depositied in the perimysium

what is the most abundant protein and what does it do

collagen

muscle integrity, elasticity, froce transmission

(muscles that contain more college produce tougher meat)

structural unit of a collagen fibril

tropocollagen,triple helix with 3 alpha chains

repeating tripeptie XY are proline and hydroxyproline

collagen matures

and forms stable cross links which increasing its tensile strength

elastin

stretch (blood vessels, lungs, tendons)

contains two AA desmosine and isodesmosine

resistant to alkalinity, acidity

contricle proteins

myosin (thick) acitin(thin)

regualtory proteins

troponin (3 subunits)

tropomyosin

streuctureal proetin

a-actinin (z line)

titin (z line to m line)

nebulin (parallels thin filament)

type 1 muscle

high myoglobin, slow twitch, oxidative metabolism (little glycolytic)

type IIa

moderate myoglobin

small fiber diameter

both anaerobic and aerobic activity

type IIX (D)

low myoblobin content

low lipid conent

type IIB

low moygoblin

quick twitch

high glycogen and glycotic metabolism

slow v fast twitch muscle appearance

slow: small fibers, darker in color

fast: larger diameter fibers, paler in color (due to anaerobic activity)

sourcers of atp for msucle ocntration/relaxation

direct phosphorylation- creatine system

oxidative phosphorylation

glycolysis

exanguination effects on meat

depletes o2 supple, anaerobic pathways lead to build up of by products that acidified the muscles (pryvate, lactic acid, Co2)

rate and extent of ph decline differences among animals due to?

differences in muscle glyocogen load at harvest

carcass chill rate

how does rigor mortis occur and 3 phases

lack of ATP production causes cross bridges to permanently stay together

delay (muscle remains extensible and elastic)

onset (muscle begins to lose extensibility)

completion (ATP depleted)

what is the purpose of carcass chilling

slows down metabolic processing to preserve the eat longer and keep from too much H+ accumulation

usually chilled at 15-20C

electrical stimulation

pre-prigor stimulation depletes ATP suplies before muscle goes into rigor and prevents cold shortenting

what is cold shortening

carcass chilled below 15C maximizes sarcomere shortening. this make the meat tougher

what are calpains

degrades costameres (linkage myofibril to sarcolemma) proteins directly attached to or near Z line (nebulin, desmin, titin)

ACTIN AND MYOSIN ARE NOT INFLUENCED BY CALPAINS

3 changes durign post morteum agin that improve tnederness

1. actin-myosin interactions are weakening by non enzymatic changes

2. enzymatic degration by calpains

3. perimysium and endomysium are weakened during aging (>10 days)

capainstatin and what happens wehn you have more or less

inhibits calpain activity

more: decreases tenderness sice it stop activity

less: increases tenderness, allows for more degration

calpain types

1: less calcium

2: more calcium

calpastatin

(there’s capin3 but we didnt talk aobut it just know there are 3)

factors that incrase calpastatin activity

breed , preharvest stress (epinephrine), growth factors (b agonists)

breeds assoc. capastatin

bos indicus have increased capastiatin activity

callipyge gnee

much hgiher calpastatin activity

beta agonsits

non-steroid grwoth stimulant affects beta adrenergic receptors (B-AR)

75 % of beef cattle are fed

orally active repartitioning agent

increases average daily gain

types fo water in muslce

bound muscle: held tightly by charges hydrophilic groups on muscle proteins

immobilized weaker attractive forces near charged proteins

fee water: held by capillary forces, independent

water holding capacity

isometric portin pf proteins is targeted

As pH increases/ decreases repulsive forces due to H+ ion or -OH concentration cause low water holding capacity

meat quality with pH

low pH: pale, soft, exudative (moderate lactate adn glycogen)

high pH: dark, frim dry (low lactate and glycogen)

depletion of glyocogen that causes DFD meat caused by what

psychological stress stress (sympathetics)

physical stress (handling, illness)

environmental stress (weather extremes, dietary restrctions)