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FOOD2000 > Meat > Flashcards

Meat Flashcards

1
Q

Difference between meat and muscle

A

Muscle is in the live animal. Meat is the dead animal.

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2
Q

Why is transport of animal to abattoir important for meat quality?

A

There are several stages involved with getting animals to slaughter:

  1. Selected, weighed, drafted on farm
  2. Groups of animals made me made up of different pens
  3. transport via road.

Loading and unloading animals can be difficult and stressful. Animals can spend considerable time in transit. At plant animals can be held for various lengths of time before slaughter in a lairage or stockyard.
> Even when carried out with care and consideration marketing process inherently stressful to animals.

  1. Carcass quality equates to carcass yield (easy to relate to economic loss)
    > total loss if animal dies during transport
    > losses of variable sizes occurs if carcass is damaged though bruising, haemorrhage, fighting.
  2. Food and water deprivation + stresses
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3
Q

What are the stresses involved with getting animals to slaughter?

A
  1. removal from home environment
  2. Loading and unloading on to vehicles
  3. often long journeys
  4. holding in unfamiliar surroundings
  5. Potential exposure to physical stress
    - Temperature
    - vibrations
    - crowding
    - speeds
    + hunger, thirst, fatigue
  6. Psychological stresses
    - breakdown of social group
    - mixing with unfamiliar animals
    - new smells
    - novel environments.
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4
Q

What are the stresses involved with getting animals to slaughter?

A
  1. removal from home environment
  2. Loading and unloading on to vehicles
  3. often long journeys
  4. holding in unfamiliar surroundings
  5. Potential exposure to physical stress
    - Temperature
    - vibrations
    - crowding
    - speeds
    + hunger, thirst, fatigue
  6. Psychological stresses
    - breakdown of social group
    - mixing with unfamiliar animals
    - new smells
    - novel environments.
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5
Q

What is PSE

A

Pale, soft, Exudative meat
mainly affects pigs
Tends to taste dry and have poor texture after cooking
(some stress susceptible breeds more prone)
large amount of exudate (reduced yield)

adrenaline–> high rates of glycolysis–> Low pH values when temp still high –> denaturation of some muscle proteins –> reduced water bound (poor WHC)
high light scattering –> less absorbed –> pale

ACUTE Stress by live animal before slaughter–> high adrenaline–> increased use of CHO

more prone in white fibres
++ Rapid chilling may reduce manifestation. Improving WHC and lean colour

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6
Q

What is DFD

A

Dark, firm, dry
occurs in all species
Poor processing characteristics, with slow or uneven formation of cured meat pigments
high pH ass. with glycogen depletion ante-mortem prevents La bacteria growth.

reduced glycogen (depletion before death) –> less LA can be formed and meat does not acidify normally–> high pH–> proteins do not denature–> high WHC –> low light scattering–> high absorbed–> dark

CHRONIC (long term) stress by live animal before slaughter

More prone in Red fibres

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7
Q

What is DFD
Why does it not keep well?
caused by?

A

Dark, firm, dry
occurs in all species
Poor processing characteristics, with slow or uneven formation of cured meat pigments, poor flavour

Has high spoilage potential so does not keep well and has short shelf life.
for two reasons:
1. DFD caused by glycogen depletion ante-mortem and is therefore characterised by very low levels of CHO in muscle. Low levels prevent growth of LA bacteria and this encourages growth of bacteria that metabolises AAs and proteins- produce unpleasant smell
2. the high pH of meat promotes this bacterial growth- increased spoilage risk.

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8
Q

What is rigomortis

A

When the muscles can no longer relax. Calcium is no longer being pumped into SR/ ER because this process requires ATP. Develops slowly.

  • determined by rate of chilling
  • carcass becomes stiffer

occurs when supply of ATP is depleted

after riggor muscle can no longer shorten

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9
Q

Adrenaline

A

promotes glycogen breakdown through a series of steps that result on activation of enzyme catalysing 1st stage of glycogenolysis (phosphorylase) –> promotes increased glycogen breakdown

(PSE- acute stress)

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10
Q

What happens when an animal is killed

A

animal supply of oxygen (&glucose & FA) to muscle ceases when blood circulation ceases.
glycogen can only be broken down by glycolysis
Thus LA accumulates–> acidifies muscle

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11
Q

two important characteristics of meat affected by acidification

A
  • colour
  • WHC

> primarily due to effects of decreased pH on muscle structure (proteins denature, myofibril proteins reach isoelectric point)

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12
Q

WHC

A

denaturation of proteins & reaching their Phi can lead to exudation of fluid from muscle fibres.
greater sarcomere shortening

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13
Q

colour changes pre rigor

A

change in proteins with acidification PM & consequent change in structure- increasing light scattering properties of contractile elements

normally- absorbed= dark appearance
increasing heterogeneous= less absorbed= paler colour

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14
Q

When rigomortis occurs is affected by

A

factors affecting levels of glycogen and CP at death & rate of PM muscle contraction

  • stress and exercise
  • rate of development reduced if carcass cooled quicker
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15
Q

factors affecting tenderness

A
  • sarcomere length (can’t be changed after rigor)
  • temperature that muscles go into rigor
    > too hot (above 15 particularly above 35)
  • hot shortening
  • denaturing occurs in proteolytic enzymes caused by combination of high temperature and low pH
  • ageing time (changes in connective tissue components of meat & weakening of myofibrils) - tenderisation faster at higher temp (post rigor) & different species.
  • temperature post rigor- keeping meat at higher temperature post rigor promotes tenderisation through increased Calpain activity.
  • ph of muscle- low pH will denature proteolytic enzyme: calpains - activity will be reduced and less tenderisation occurs. (ass. with why heat shortening thought to be less tender- low pH at high temp)
  • marinating and injecting (salt solutions with acids- break muscle structure down possibly by encouraging the action of collagenases and cathepsins that work at low pH).
  • diet: feeding cattle vit D 3: imp for calcium & phosphorous met- higher calcium ass. with high calpain activity (‘frees’ it)
  • poor slaughtering handling: PSE and DFD
  • carcass damage
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16
Q

issues that can affect meat quality before rigormortis

A
  • Hot shortening
  • cold shortening
  • Stress
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17
Q

What does tenderisation result from

A

activities of proteolytic enzymes present in muscles
- normal role is breakdown & recycling of proteins

2 main sorts of enzymes involved
1. Calpains (thought to be most imp) –> degraded at low pH, activated by calcium ions

  1. Cathepsins
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18
Q

Pre rigor interventions to increase tenderness

A

Reduce stress.

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19
Q

live animal interventions to increase tenderness

A
  • diet: feeding cattle vit D 3: imp for calcium & phosphorous met- higher calcium ass. with high calpain activity (‘frees’ it)
    (+ improve quality and function as a functional food with diet of animal- increase levels of PUFAs)
  • reduce stress during transport
  • breed animals with favourable genes
  • vit E supplement (naturally get for grass fed)- reduce drip loss, prevent PSE in pigs
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20
Q

Post rigor interventions to increase tenderness

A
  • marinating and injecting
  • salts and acids
    CaCl2: high [] effects on flavour and taste, promotes faster oxidation of heam pigments so that surface of meat turns brown sooner and therefore has a shorter shelf life. (overcome if + vit C)
  • naturally occurring enzymes (papain) - proteolytic
  • communition
  • lower quality cuts, older animals- inherently tougher. - mincing or grinding , breaks up connective tissue or fat.
  • mechanically recovered/ deboned meat:
  • pressure treatment: shock wave while underwater.
  • making into sausages/ reformed or restructured meats.
21
Q

Three types of sausages

A
  1. fresh
  2. cooked
  3. dry/ fermented: LAB introduced as starter culture: use CHO and produce LA. regulating temp and humidity
22
Q

What is meat quality?

A
  1. functional quality (desirable attributes) ass. w consumer
  2. conformance quality (consumers specifications)

functional quality

  • can mean different things for different people- depending on culture/ experience…
  • concepts of quality vary over time (e.g. pigs for lard)

quality components

  • yield & gross composition
  • appearance & technological characteristics
  • palatability (texture and tenderness, juiciness, flavour)
  • wholesomeness (safe to eat & beneficial to health)
  • ethical quality

Some quality components are conflicting: e.i. Juiciness and health (higher fat= more juicy but less healthy)

23
Q

Why is WHC important

A
  1. drip or exudate that results from meat with poor WHC detracts from appearance of meat
  2. Loss of drip leads to
    - weight loss
    - in processed meats; poor WHC may reduce water retention and yield of product
  3. WHC is thought to influence the perceived juiciness of fresh meat after cooking
24
Q

Factors influencing quality

A
  1. on farm
    - age
    - nutrition
    - breed
    - feeding
    - maturity at slaughter
    - genetic influences- (late Vs early maturing, fatness, calpain levels (humped breeds)
    stress of handling to slaughter
  2. post mortem
    3.
25
Q

Major factors influencing Pork quality

A

influence weather muscle

  • shows DFD or PSE
  • has abnormally low pH
  • levels of intramuscular fat - change with breed
  • genes: halothane & RN gene
  • taint- in boars

halothane gene:
PSE meat- susceptibility to halothane gas (hyperthermia- rapid pH fall) ass. w stress susceptibility
also ass with positive attributes of muscularity & conformation
RN gene: negative effects on pork pH, WHC, colour, drip loss, cooking ass & processing yield. - very low pH

26
Q

Bruising

A

Bruised tissue probably has no greater initial microbiological load than normal tissue but tends to be handled more & may pick up a higher microbial load

  • too high/ too low stocking density during transport can leas to more bruising.
  • long periods without food
  • chronic stress
27
Q

Carcass quality effects

A
  • mortality of animals during transport: total loss of value
  • carcass damage
    *bruising (larger microbial load ass handled more)
    *skin lacerations
    ass. water and food access, long journeys.
  • skin blemishes in pigs (issue with rind on products)
  • reduction of live weight and carcass yield by initiation and transport- ‘shrinkage’
  • loss of gut fill and excretory losses.
  • pigs: 9-18h after last meal
    *ambient temp
    (fed too soon: pigs larger mortality, hygiene issues with full gut-> build up of pathogenic bacteria, contamination in abattoirs)
28
Q

What is acidification in muscle caused by

A

PM breakdown of glycogen to LA

29
Q

Measures to reduce prevalence of PSE and DFD meat

A

+Improve pre- slaughtering handling
- ensure right stocking density in transport
- prevent/ reduce fighting: try and transport pigs from same rearing pens together as much as possible, spray with androsterone, tranquillisers,
- good conditions in lairage: access to water and meal if there for long periods of time (replenish muscle glycogen -DFD & ‘shrinkage’) [pigs feed if more then 12 hrs]
(conditions that allow animals to rest and calm down–> rest in unmixed groups)

+select genotypes that aren’t as susceptible to stress (no halothene gene in pigs)

  • cool pigs down quickly= so that the temperature is lower when pH drops. CS is less of a potential problem in pigs due to rapid RM development
  • AO supplementation in live animal: VIT E- reduce drip loss and prevent PSE in pigs
30
Q

Stunning
why
methods

A

important to mobilise animal to facilitate severing of blood vessels to kill it.
+ prevents animals feeling pain or distress during exsanguination
+ relaxing body= benefit carcass quality

3 types
1. use of mechanical instrument
- captive bolt and concussive stunning
captive bolt use in pigs may lead to PSE meat.
2. electrical current passed through brain
- in poultry, pigs, sheep
- 3 s of current
3. immersion in gas
- unconscious and killed by CO2 (pigs- lower incidences of PSE)

31
Q

Why would you not electrically stimulate or use a captive bolt a pig?

A

Prolonged application of electrical stunning currents such that it passes through pigs body and head- can stimulate the musculature and lead to faster acidification –> PSE

+ can sometimes cause problems of blood splash, haemorrhaging or broken bones- especially in pigs (high voltages when animal not properly restrained)

  • violent muscle contraction that results from passage of current
  • particularly broken backs and haemorrhaging can occur in pigs.

better to stun with CO2. (less haemorrhaging or broken bones)

captive bolt- leads to a lot of convulsions

  • promote faster muscle acidification
  • may result in PSE meat.
32
Q

Carcass chilling

why chill

A 
animal body temp at death 37- 39
rate of loss depends on 
- size 
- subcutaneous fat 
- air circulation

–> reduce microbial growth on carcass surface and reduce evaporative weight loss
may also reduce manifestation of PSE in pork

33
Q

Influence of temperature on muscle metabolism

A

Activity of enzymes are temperature dependent
different cooling rates can affect:
- rates of pH fall through LA production [minimum rate abt 10 degrees max 37)
- disappearance of CP and ATP
-speed of onset of RM - rate of ATP depletion

draw graph of relationship in beef

34
Q

3 practical implications of different cooling rates of carcass cooling & muscle temp

A
  • cold shortening
  • thaw rigor
  • hot shortening
35
Q

Cold shortening

A

muscle is cooled below 10 degrees before the onset of rigor= meat is tougher after cooking due to shorter sarcomere length.

the result of rapid chilling of carcasses immediately after slaughter- before glycogen has been converted to LA.

low temperatures- Calcium pump responsible for pumping calcium back into SR and ER doesn’t function well - therefore calcium ions leak out causing muscle contraction- and cannot be removed. & ability of mitochondria to sequester calcium also reduced.
+ red muscle fibres are more prone= less well developed SR.

Chicken and pigs less prone because of high rates of PM development.
lamb most prone
beef- cool slowly cause of size

if muscles are physically prevented from shortening- length and texture remain constant
Electrical stimulation- to ensure that rigor development occurs before being cooled- because carcass temp still high- after stimulation ceases the SR can take up Ca previously released- muscle goes into rigor in a relaxed state.

36
Q

ideal tenderness in beef- what temp?

A

beef should be cooled as rapidly as possible to 15C and enter rigor at this temp- avoid hot and cold shortening.

window: between pH 6 and temp 35 (hot shortening) and below pH 6 and 12C (cold shortening)

37
Q

thaw rigor

A

rate of cooling is too high before onset of rigor- on thawing muscle shortens severely.–> rapid and massive release of Ca ions & glycolysis being completed very rapidly (cant relax)
very large amount of drip are lost.

38
Q

Electrical stimulation

A

method to accelerate rigor development- causing intense muscle contractions which use up remaining glucose in muscle.

  • prevent cold shortening
  • tenderise meat & improve appearance and colour (possibly though weakening muscle structure, stimulating calpains)
39
Q

heat shortening

A

If the pH decline is too fast & the ultimate level is reached while the temperature is still high– muscles will enter rigor at a high temperature–> thougher (less then CS)

pH below 6 but the temperature remains higher then 35C
rapid depletion of ATP stores

  • increased toughness
  • effects of proteolytic enzymes (calpains) - denatured
40
Q

Hot processing

A
  • method to cool carcass more evenly and quickly (cheaper)
    involves removing muscle from skeleton when hot.
    adv:
    better yield
    reduce refrigeration costs - save E
    more uniform colour
    better WHC

Dis:
weird shape as not fixed by skeleton during rigor
may be slightly tougher (heath shorten or CS)
Harder to handle

41
Q

Carcass suspension

A

Stretching may increase sarcomere length = more tender

hook in pelvis/ hip= weight of legs pulls muscles down ( LD stretched & muscles on outside of hip) BUT takes up more room in the freezer, some muscles toughen

tendercut: LD stretched by severing vertebral column in pelvic region so weight of forequarter part of carcass is not supported by backbone but only by muscle. ADV: hung normally from Achilles tendon (easier to handle + less space taken up)

42
Q

meat packaging

A

affects the colour of meat
- consumers prefer bright red colour

major role to control gas atmospheres in contact with its surface & so influence the reaction of heam pigments.

43
Q

packaging in controlled gas mixtures

different types

A

major role to control gas atmospheres in contact with its surface & so influence the reaction of heam pigments.
imp gases
- oxygen: oxidises/ oxygenates
- Carbon dioxide: inhibits bacterial growth
- Nitrogen: inert and sometimes used as a ‘ballast’ gas

Using very gas-permeable plastic film allow oxygen from air to penetrate easily and react with myoglobin to give bright red oxymyoglobin. –> only stable for a few days before MetMb becomes an issue

Modified atmosphere packaging (MAP) to extend shelf life
more oxygen/ CO2 then in the air.
relatively impermeable plastic is employed & the pack is filled with a gas mixture containing 60-80% oxygen in CO2.
high oxygen- brighter red, deeper oxygen penetration
higher CO2- inhibits undesirable microbial growth
–> concern is that increased shelf life could enable growth of pathogenic bacteria to levels that could make meat unsafe.

Vacuum packaging: (low gas permeability) no oxygen therefore very thin MbO layer- anaerobic conditions –> dark purple appearance
not good for retail but good for storing and transporting boneless primal joints where colour is not important
As the oxygen is consumed by enzymes in the meat - CO2 is produced- inhibits spoilage by undesirable bacteria and encourages LA bacteria growth
meat lasts for a much longer time 5/6 weeks

Controlled atmosphere packaging (CAP)- like MAP but monitored and new gases can be added

44
Q

Meat colour
dependent on

affected by

A

freshly cut= purple because the pigments in the deoxygenated form –> cutting Mb in the surface reacts with oxygen to form the desirable bright red MbO (takes 15 min to 1 hr ‘blooming’- depth depends on oxygen penetration)

dependent on the pigment
Oxymyoglobin (MbO)- bright red (exposure to oxygen- oxygenation) - ass. low levels of reducing enzymes
Deoxymyoglobin (Mb)- purple
Met myoglobin (MetMb)- grey- brown (oxidation)

affected by:
++aged meat- brighter red- oxygen can diffuse more, lower reducing enzyme makes pigment more prone to oxidation
++storage temperature - lower temp diffusion of oxygen and reducing enzymes decrease. more Oxygen present and less reducing enzyme- brighter red at low temp

  • AO can have an impact (also help maintain flavour) : prevent oxidation –> to metMb (brown) Vit E in live animal, VIT C injected into processed meats
45
Q

How can meat colour be controlled

A
  • use of packaging: modified atmosphere packaging (MAP) —> to promote oxygenation of Mb= brighter red colour
46
Q

Use of antioxidants

A

Prevent against oxidation to extend shelf life of meat by protecting its appearance and inhibiting

3 synthetic commonly used 
propyl gallate (PG) 
butylated hydroxyanisole (BHA) 
butylated hydroxytoluene (BHT) 
\+ Vit C + Vit E

Vit C injected

Vit E- dietary supplement in live animals:

  • reduce drip loss
  • prevent PSE in some stress- susceptible pigs
47
Q

Interventions to improve meat quality

A

before death:
- feeding animal antioxidants
(vitamin supplements easy in feedlots & grass fed may benefit from higher Vit E in pasture)
- reduce stress
- ensure adequate water and food (if needed to replenish muscle glycogen stores in lairage)

death:
- poor antemortem handling can produce PSE/DFD meat
- use appropriate killing and stunning method to prevent stress

pre-rigor

  • suspension - tendercut
  • electrical stimulation- prevent CS
  • control temperature- stay in window - prevent hot/ cold shortening

post rigor

  • ageing (breakdown of muscle proteins)
  • packaging - colour & microbial content
  • antioxidants - colour & flavour
48
Q

Early post mortem impacts on meat quality

A
  • temperature

- glycogen levels in the muscle at time of death

49
Q

Factors affecting palatability

A
  • physical maturity (amount of collagen cross links in the muscle)
  • gender (ossification
  • pre and post slaughter factors
  • pH
  • fat and partitioning of fat
  • WHC
  • colour
  • collagen
  • doneness
  • connective tissue

FOOD2000 (5 decks)

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