meat test 3

four major functions influencing homeostasis in the muscle

oxygen concentration (metabolism), pH, temperature, energy

what happens during oxygen concentration

removal of blood or exsanguination marks the beginning of postmortem changes, drop in blood pressure, homeostatic control mechanisms kick in, protective/ survival mechanism to compensate, increase in heart rate to maintain circulation, peripheral vessels constrict to prioritize blood flow, 50% of remaining blood redirected to vital organs

what are the consequences of no oxygen concentration

muscle not converted to meat until metabolism stops, oxygen supply depleted: TCA cycle and electron transport failing, homeostatic maintenance: shifting to anaerobic metabolism

what happens to pH

decline of muscle pH

why does pH change

accumulation of lactic acid, greatly variable rate of decline, normal decline pattern

what are the consequences of pH change

changes in meat quality attributes, color and protein functionality

what happens to temperature

briefly increasing postmortem and then decreases

why does temperature change

rate of metabolism, size and location of muscles, predominate muscle fiber type, duration of metabolism, fat insulation, slaughter: handling, stress, stun/stick

what are the consequences of temperature change

microbial growth, protein denaturation, oxidation

what happens to energy

gradually depleted

why does energy change

two sources of ATP: glycolytic metabolism, creatine phosphate; how is ATP used

what are the consequences of energy

rigor sets in when ATP depletes

phases of rigor mortis

delay phase, onset phase, completion phase

what is the muscle status at rigor completion (tension, metmyosin and actin binding, two charts)

maximum tension, metmyosin tightly bound to actin permanetly

what is rigor resolution

important phase after rigor mortis, proteins on z-disk will degrade which is caused by calcium being released to then release calpain

short term stress impact on meat

rapid pH decline, few minutes before slaughter, PSE meat, pigs

long term stress impact on meat

slow pH decline, at expense of glycogen storage, DFD meat, ruminants

what is PSE

pale, soft, exudative

what causes PSE

rapid pH decline

what is DFD

dark, firm, dry

what causes DFD

slow pH decline

bound water

4-5%

immobilized water

variable

free water

surface water

effects of pH on protein functionality

as pH decline decreasing reactive groups on proteins available for water binding

effects of pH on WHC

greater the pH the greater the WHC

what is the isoelectric points

5-5.2

immobilization effects

blood pressure increased dramatically after stunning, handling is key, stun-to-stick interval, goal is rapid bleeding, no blood splash

cold shortening

sudden shortening pre-rigor caused by nervous stimulation, induced by cold temperature, before rigor onset, too cold, cold-induced nervous response, similar to muscle contraction, not much ATP left for relaxation

thaw rigor

severe rigor caused by thawing muscle that was frozen pre-rigor, developing when thawed, sudden release of ___ into sarcoplasm, physical shortening of unrestrained muscle, less in muscles restrained by bones

heat ring

happens to lean meat, two different color tones, less than 0.25 in backfat in beef, less than 0.1 in backfat in lamb, not chilled properly, low glycolytic metabolism, high pH,

optimum chilling temperature during rigor onset

15-16 degrees celcius because want to avoid heat ring, cold shortening, and thaw rigor

pre-rigor deboning

cutting, deboning, and grinding immediately after slaughter; glycolysis is less extensive; greater ultimate pH: 6-6.7; better WHC, max WHC for processed meats

electrical stimulation mechanisms

cold shortening prevention: extremely rapid glycolysis and rigor onset, accelerated proteolysis: calcium release, physical disruption of muscle structure: extreme contractions, carcasses can be chilled faster

electrical stimulation outcomes

stimulates contraction, improves meat quality and processing capability

structure of myoglobin

8 alpha helices, heme ring, iron with 6 binding sites, distal histadine

role of myoglobin in meat color

the more there is in a muscle the darker the meat

heme ring

contains iron at center, 4 pyrrole ring structure

iron 6 binding sites

4 bonded to heme ring, 1 bonded to proximal his, 1 bonded to ligands

deoxymyoglobin

ferrous (Fe++), very low O2 pp, only water to bind, uncut or vacuum packaged meat, purplish-red or purplish-pink color

oxymyoglobin

ferrous (Fe++), no change in iron’s valence, exposed to oxygen or air, at least 40 torr of O2 pp, 1 binding site occupied by diatomic oxygen, distal histidine stabilizes Fe-O2 bond, “blooming” meat cuts, over wrapped, Hi-Ox MAP, purplish red or purplish pink color, not stable, oxidized easily to ferric (Fe+++)

metmyoglobin

ferric (Fe+++), increase in iron’s valence, low O2 pp: decreased by O2 consumption by cellular respiration, low MRA, low O2 transmission rates: surface contamination bc aerobic bacteria use O2, oxidized meat cutes by prolonged exposure to O2, deep layer of OMb without enough O2, brown

carboxymyoglobin

carbon monoxide bound to the heme group, bright red

sulfmyoglobin

low oxygen conditions or during prescene of certain bacteria that produce hydrogen sulfide, green color

nitrosomyoglobin

nitrite or nitrate reacts with myoglobin, inhibits bacterial growth, reaction is key part of curing red meat, bright red color

premature browning

development of a well-done, internal cooked apperance at end point temperatures LOWER than those needed to kill pathogenic bacteria, food safety issue

persistent pinking

a pink/red color remaining after a SAFE endpoint temperature is reached, costly problem to meat producers and food service due to consumer rejection, a quality issue

retail display conditions

sales loss, annual sales loss around $1 billion in US

antioxidant preservation

feed supplement to animals (vit E), preservatives sprayed on animals: vit E/C and plant extracts and synthetic antioxidants, active packaging: antioxidant-coated film

delay phase of rigor mortis

immediately after exsanguination

onset phase of rigor mortis

within hours, species dependent

completion phase of rigor mortis

within 24 hrs, species dependent

compare the rigor mortis phases in

ATP availability, CP availability, formation of actomyosin cross-bridges, extensibility of muscles

ligands that iron will bind to

O2, CO, H2O, NO, etc

lowering carcass temperature to prevent

protein denaturation, enzymatic activities, bacterial growth