Muscle to Meat

Question 1

Describe the process of muscle contraction

Answer 1

• AP passes from ventral horn of cns to motor unit
• Releases Ach at motor end plate stimulating action potential along the muscle fibre
• Stimulate the release of Ca2+ from the sarcoplasmic reticulum which act on troponin and tropomyocin, revealin binding sites that allow myocin heads to “grab and flick” the actin strand

Question 2

Describe the process of prevention of contractiob

Answer 2

• Ach broken down by acetylcholinesterase - reduced AP
• Sacroplasmic reticulum stops reeasing calcium ions and begins sequestering them
• Abscence of Ca2+ = troponin andand tropomyosin reconfigure preventing action of the myosin heads

Question 3

Describe the process of rigor mortis

Answer 3

• At rigor, when the supply of ATP is exhausted, myosin heads remain irreversibly locked onto actin, leading to a rigid structure
Onset depends on sustained ATP production vs consumption. Drop of ATP stimulates process

Question 4

Describe three ways of assessing meat quality

Answer 4

• Water holding capacity: The pH of meat influences the extent muscle proteins are charged, which is necessary to attract and hold the dissociated form of water. Most proteins in meat lose their charge between pH 5.1 and 5.5, which is close to ultimate pH of meat. In this range muscle releases water.
• Colour and paleness: The colour is influenced by the presence of myoglobin. Bright red colour in presence of oxygen (blooming) is synonymous with freshness. Different muscles will have different colour, as there is a higher proportion of myoglobin in slow muscle than in fast muscle.
• Succulence / juiciness (subjective trait): Succulence is an eating quality, often related to the level of fat and moisture in cooked meat. Excessively lean carcass confers less juicy meat. Perceived tenderness and succulence can be improved by simply increasing the amount of fat.

Question 5

How can meat tenderness be measured?

Answer 5

Measuring shear force and the myofibrillar fragmentation index. Also subjective methods, such as taste or eating quality assessment can also be used

Question 6

Give four factors that affect meat tenderness

Answer 6

• Age of the animal: Collagenous tissues in meat can increase with age. Age may also raise the number of intermolecular collagen bonds.
• Kind of muscle: White muscle like Longissimus dorsi, is generally less tender than red muscle (Psoas major and P. minor).
• Amount of sarcomeric shortening during rigor mortis: The faster the rate of glycolysis the greater the likelihood of sarcomere shortening.
• Meat maturation: Longer the time leaving meat in chilling room, more tender the meat (due to proteolysis). This process is called meat ageing or conditioning.

Question 7

Describe the benefits of ageing meat

Answer 7

Increased tenderness, flavour and aroma

Question 8

Give three potential problems with aging meat

Answer 8

Excessive dehydration of the carcass;
Overgrowing of moulds;
The potentially overgrowing of pathogenic microorganisms

Question 9

What is electrical stimulation and what are the theories behind it

Answer 9

An electric current is transmitted through the carcass of animals that are freshly slaughtered and eviscerated.
The basis of the efficacy of ES is its ability to fast track post-mortem glycolysis. Electrical stimulation hastens the onset and resolution of rigor mortis thereby reducing processing time and labour and plays a vital role in improving meat tenderness and other meat quality traits.

Question 10

What are the limitations of Electrical stimulation?

Answer 10

However, ES may have negative impacts on some meat quality traits such as colour stability and water holding capacity in some animals.
ES is applied after exsanguination, within 1h of slaughter. It can be either low current (up to 100 volts) or high current (100-500 volts)

Question 11

What muscle are carcasses normally hung from?

Answer 11

Gastrocnemius

Question 12

How can cold shortening be prevented

Answer 12

By suspending the carcass by the obturator foramen, the muscles in the gluteal area will be stretched, reducing the likelihood of problems such as cold shortening.

Question 13

Name three other ways in which meat tenderness can be improved

Answer 13

• Mechanical methods: mincing.
• Use of proteases: for example papain (papaya), bromelin (pineapple skins) and ficin (fig trees).
• Marination: Use of NaCl, polyphosphate, CaCl2 and Bicarbonate

Question 14

Describe the difference between meat and carcass quality

Answer 14

• Meat quality is about compositional quality (lean to non-lean, such as fat, ratio), physical properties and eating qualities.
• Carcass quality is about conformation, fatness and weight

Question 15

Describe Dark cutting beef and the mechanisms that produce it

Answer 15

Dark Cutting Beef (DCB), or Dark Firm Dry (DFD) is a condition associated to incomplete acidification. While normally red meat is expected to reach a pH of approximately 5.5 to 5.6, DCB will have a pH higher than 6.0 at 24h post slaughter.
It is normally caused due to depleted muscle glycogen in stressed animals, with an early onset of rigor mortis.

Question 16

Describe the appearance of dark cutting beef

Answer 16

The meat looks darker than normal and is able to retain structural water, hence it is prone to rapid spoilage. Additionally, the meat is tougher than expected as actin-myosin complex is still present.

Question 17

Describe Pale soft Exudative and the process that causes it

Answer 17

Pale Soft Exudative (PSE) is primarily a condition of pork. It occurs due to an accelerated glycolysis after slaughter, with rapid build-up of lactic acid. In fact, if the pH is lower than 6.0 in less than 45min post-slaughter, it is likely that the pork carcass will be affected with PSE.
Some characteristics of the condition are:
• Rapid onset of rigor mortis;
• Excessive drip loss from cut surface and cooking;
• Paleness due to high reflectance from wet surface.
The condition has been associated to a mutation in the ryanodine receptor (RYR1) causes uncontrolled calcium release, leading to rapid glycolysis.

Question 18

Describe cold shortening

Answer 18

Where the muscle is cooled below 10 degrees before it has reached rigor mortis. Accumulation of cystolic Ca2+ = shortening of the caracass by up to 1/3

Question 19

Describe boar taint and the mechanisms behind it

Answer 19

Boar taint is an unpleasant urine-like odour of entire boars and in a minority of pigs.
Causes:
• Sex steroids, like androstenone, deposited in intramuscular fat.
• Microbial breakdown of tryptophan in gut to skatole and indole; which is absorbed and, if not broken down effectively (as is in boars), deposited in adipose tissues.

Question 20

Describe management methods for boar taint

Answer 20

One of the reasons for carrying out castration in male pigs it is to reduce the proportion of carcasses affected with boar taint. However, husbandry strategies can also be effective. Avoiding overcrowding and the use of slatted floors to reduce faecal contamination could reduce the incidence. Alternative, earlier slaughter of males (at a younger age) could also reduce the incidence of boar taint.

Question 21

Describe the beef classification scheme

Answer 21

Under the Beef Carcase Classification Scheme (BCC), abattoirs which slaughter more than 75 adult bovine animals per week on a rolling yearly average basis, are required to register and classify carcases.
Small scale operators (an operator of an approved slaughterhouse at which not more than 75 adult bovine animals are slaughtered/week) may choose to register and classify adult bovine animals under the BCC scheme.

Question 22

What is the purpose of the beef classification scheme

Answer 22

The purpose of the scheme is to make sure that adult bovine animals are uniformly classified and producers are guaranteed fair payment for cattle delivered to slaughterhouses, based on the Community (European Union) Grading Scale. This classification also aims to improve the transparency of the market in carcases to the benefit of all sectors of the industry.

Question 23

Describe conformation categorization in beef carcasses

Answer 23

• Conformation: it is a visual assessment of the overall shape and flesh coverage of the carcase. There are five classes (E, U, R, O and P). To be given an E classification, the carcase must have excellent conformation and must have no defects of its essential parts. In cases of U, O and P conformation, a carcase with three essential parts that are not of a homogeneous nature will be placed in the class that applies to two of the three parts. These categories are further divided into upper (+) and lower (-) bands

Question 24

Describe assessment of beef fat cover

Answer 24

The fat class is determined by a visual appraisal of external fat development. The assessment can result in five classes ranging from 1 (very lean) to 5 (very fat) with classes 4 and 5 being subdivided into leaner (L) and fatter (H) bands.

Question 25

Describe the overall classification of lamb in slaughterhouses

Answer 25

Although no mandatory in sheep, most UK slaughterhouses grade their carcases on the EUROP payment grid (as in beef).
The grid was introduced in the 1970’s; the reason for its introduction was so that a uniform classifying system could be used throughout Europe,
it also meant that producers could be rewarded for supplying lambs with the carcasse classification that the market demanded

Question 26

Describe the conformation classification in lamb

Answer 26

The conformation class is determined by a visual appraisal of shape, taking into account carcase blockiness and fullness of the legs. No adjustment is made for the influence of fatness on the overall shape. There are five main classes: E,U,R,O,P (where E=excellent to P=poor)

Question 27

Describe the fatness grading in lamb

Answer 27

The fat class is determined by a visual appraisal of external fat development. There are five main classes ranging from 1 (very lean) to 5 (excessively fat). Classes 3 and 4 are sub-divided into L (leaner) and H (fatter).

Question 28

Describe the overall pig classification requirement include a definition of Clean pigs

Answer 28

Slaughterhouses that slaughters more than 200 clean pigs per week (averaged over a 12-month rolling period), must be registered with the Pig Carcase Grading Scheme.
Clean pigs are animals that have not been used for breeding.

Question 29

What does the Pig Carcasse grading scheme dictate rules on?

Answer 29

Registered slaughterhouses must follow the rules that describe how to:
• dress carcases;
• weigh carcases;
• grade carcases for lean meat content (the grade is then marked on the carcase or documented).

Question 30

According to EU specification what parts must be removed before weighing a pig carcasse

Answer 30

• Tongue;
• Bristles (hair);
• Hooves;
• Genital organs;
• Flare fat;
• Kidney;
• Diaphragm.

Question 31

According to UK specification what parts can be left in before weighing a pig carcasse

Answer 31

• Kidneys;
• Flare fat;
• Diaphragm.
• Additionally, according to the UK specification the tongue may be left in or taken out

Question 32

Describe the direction for weighing pig carcasses

Answer 32

The dressed carcase must be weighed for its warm weight. Wherever possible, this must be done not more than 45 minutes after the pig has been stuck.

Question 33

Describe the process of grading a pig carcasse

Answer 33

Pig Carcase Grading Scheme must also assess and grade the lean meat content of the carcass.
The assessment is an estimate by measuring the fat thickness over the muscle Longissimus dorsi, 6.5cm from the dorsal mid-line at the last rib.
The measurement is performed by using an optical probe. There are several probes available in the market. However, the probe to be used must be one of the approved ones by legislation.

Question 34

What must carcasses destined to export uncut to another EU member state be marked with?

Answer 34

• The appropriate letter from the grading scale above;

* The percentage lean meat content.