Help
Options
Didn't know it?
click below
click below
Knew it?
click below
click below
Don't Know
Remaining cards (0)
Know
retry
shuffle
restart
0:00
Embed Code - If you would like this activity on your web page, copy the script below and paste it into your web page.
Normal Size Small Size show me how
Normal Size Small Size show me how
Animal Phys L7
| Question | Answer |
|---|---|
| Factors influencing pH decline and meat quality | genetics nutrition environment handling and transport large (rest period before laughter) immobilisation (stunning method) chilling temperature and rate |
| muscle remains _____ after death for hours to weeks | metabolically active |
| conversion involves | energy metabolism shift from aerobic to anaerobic pH decline from Lactic acid accumulation ATP depletion -> rigor mortis enzymatic degradation -> tenderisation oxidation |
| Stunning methods | CO2 stunning (pigs) Electrical stunning (sheep, poultry) Captive bolt (cattle) |
| CO2 stunning | occurs in pigs only not cost effective for larger animals pigs stunned in groups (reduces stress) O2 deprivation, loss of consciousness |
| Electrical stunning | sheep and poultry induces tonic-clonic seizure followed by exsanguination |
| Tonic phase (electrical stunning) | rigid muscles, no breathing |
| Clonic phase (electrical stunning) | relaxation, kicking, vocalisation |
| Captive bolt | penetrating percussive stun causes irreversible brain trauma must be followed be exsanguination to ensure death |
| Exsanguination | cutting major blood vessels in neck causes extreme blood loss removes oxygen and nutrients |
| Order of tissue death | nerves: less than 15 mins muscle: several hours |
| Rigor mortis | occurs when ATP depleted -> muscles can't relax actin-myosin cross bridges form permanently defines sarcomere length, |
| Short sarcomeres | tougher meat |
| long sarcomeres | more tender meat |
| factors influencing rigor | temperature muscle fibre type pre-slaughter stress glycogen reserves |
| Postmortem energy metabolism Lack of O2 shifts metabolism to....... | Glycolysis, which produces lactate |
| Postmortem energy metabolism Lactate accumulation causes..... | pH to fall from approx 7.0 to 5.5 |
| Too rapid pH decline | protein denaturation, causing pale, soft exudative meat (PSE) |
| Too slow pH decline | dark, firm, dry (DFD) meat |
| ATP powers | ion pumps muscle relaxation and homeostasis |
| When ATP depletes | ion gradients collapse membranes lose integrity cellular compartments break down |
| What happens to the mitochondria when there is no oxygen? | mitochondria stop producing ATP Reactive oxygen species form, causing oxidative damage Antioxidant defences fail |
| ROS | Reactive oxygen species |
| Consequences of mitochondrial failure and oxidation | protein and lipid oxidation -> reduced meat colour and flavour Loss of membrane integrity -> drip loss (exudate) |
| Meat ageing | time dependent process postmortem that improves tenderness caused by protein degradation (not bacterial spoilage) |
| Warner-bratzler shear force (WBSF) | measure of meat tenderness lower WSBF = more tender, better consumer acceptance |
| meat tenderisation | structural myofibrillar proteins broken down |
| two main processes of meat tenderisation | enzymatic (protease driven) non-enzymatic (oxidative and physical) |
| Proteolytic systems in meat tenderisation (calpain system) | Main enzyme: calpain Activation: Ca2+ dependent Majo contributor to myofibrillar degradation acts early postmortem; responsible for Z-line breakdown |
| Proteolytic systems in meat tenderisation Lysosomal (endolysosomal) | Main enzyme: cathepsins Activation: acidic pH non-specific protein degradation limited due to neutral postmortem pH |
| Proteolytic systems in meat tenderisation Proteasome (ubiquitin) | Main enzyme: Proteasome Activation: ATP-dependent specific protein degradation limited postmortem (no ATP) |
| Calcium's role | Loss of SERCA activity leads to cytosolic Ca2+ increases high Ca2+ activates calpains and Z-line degradation (structural weakening) |
| Calpain system vs Protein turnover (live muscle) | Calpain "unpacks" myofibrils for further degradation by proteasome/lysosome |
| Calpain system vs Protein turnover (postmortem muscle) | Only calpain remains active (others need ATP of low pH) Therefore, cal pains drive tenderisation |
| Lipid peroxidation | Oxidation of membrane lipids causes cell leakage (drip loss) |
| Causes of lipid peroxidation | endogenous ROS production bacterial spoilage |
| Effects of lipid peroxidation | increased drip loss (less juicy meat) deterioration of flavour reduced shelf life |
| Deoxymyoglobin | reduced Fe2+ purple/red colour |
| Oxymyoglobin | oxygenated Fe2+ Bright red (the yummiest one) |
| Metmyoglobin | Oxidised Fe3+ Brown/ grey looks yucky but usually ok |
| what determines meat colour? | oxygen exposure and oxidation |
| pH and temp effects on meat quality | caracsses rapidly chilled for food safety controlled chilling balances pH decline and temp drop |
| cold shortening | cooling too quickly pre-rigor sarcomeres lock into shortened position results in tougher meat texture |
| muscle shortening postmortem | continues for up to 24 hours postmortem rate depends on temp and pH isometric tension increases and muscles contract and then stabilise in rigor |
Created by:
sakelleher29
Popular Life Science sets