Meat quality
   
To the consumer an enjoyable meat eating experience is one that associates meat with being tender, juicy and flavorsome. Consumer studies show that tenderness and flavour are the most important characteristics determining the acceptability of meat. However, there is a wide range of other attributes that can potentially influence acceptability of meat.
                     
Visual appearance is very important in determining the likelihood of purchase. Bright red in the case of beef and lamb and pink in the case of pork is the desirable colour of lean meat. The amount of fat can also influence meat’s visual appeal.
                     
Less tangible intrinsic quality characteristics can be inferred from information on the label, such as perceived nutritional value, freshness and microbiological safety. Extrinsic quality attributes also influence acceptability of meat. These include elements such as animal welfare and the impact of production on the environment.
                     
MLC Blueprints
 
The key factors that affect meat quality have been intensively researched and are clearly set out in the MLC Blueprints for the production of consistent eating quality in beef, lean and tender lamb and quality pork.
                     
  •
•
•
•
•
•		 Age – there are clear differences in the attributes of meat from young and older animals.
Breed – the observed differences from various breeds are small for cattle and sheep. There are known breed effects in pigs.
Gender – is a factor but modern production methods have reduced variability.
Fat content – marbling (intra muscular fat) can increase juiciness and flavour scores.
Diet – is an important factor in fat type, which in turn affects flavour.
Production systems and pre-slaughter handling – the avoidance of stress in the live animal is important in livestock production, during transport and when the animal enters the abattoir. Before slaughter it can cause an abnormal change in the pH of the muscles and can cause pale, soft exudative (PSE) or dark, firm and dry meat affecting both tenderness and flavour.

Download a pdf of the Blueprint guidelines for
Beef
Pork
Lamb

  
Tenderness
 
There are a number of factors that can influence the tenderness of meat:
 
  •



•








•



•
 Muscle features – the amount and solubility of the connective tissue (primarily collagen) results in differences in tenderness between the different muscles. Tougher muscles with higher amounts of collagen are best cooked slowly to solubilise the collagen and thereby tenderize the meat.

Chilling conditions – rigor mortis (the stiffening of the carcase) occurs naturally following slaughter. Muscles shorten as they go into rigor and the pH of the muscle (measure of acidity or alkalinity) falls. The amount of muscle shortening affects the meat’s tenderness.

If carcases are enter rigor mortis below 10-12°C, ‘cold shortening’ of the muscle fibres can occur, causing toughness and preventing tenderisation through ageing. Cold shortening is a problem where rapid chilling systems are used, particularly for sheep carcases where the low volume of meat means the muscle cools very rapidly. Similarly, if carcases enter rigor mortis above 20°C, ‘hot shortening’ occurs. The reduction in tenderness is not so appreciable as in cold shortening.

Electrical stimulation – the application of an electric current to the carcase following slaughter reduces the pH of the muscle more quickly and hastens the onset of rigor mortis. Not only can it prevent cold shortening, it can result in early tenderisation. High voltage systems are particularly effective in lamb and pig carcases.

Hanging – the method of carcase suspension influences the degree of tension which muscles are under when rigor mortis occurs. Suspending lamb, beef and pig carcases from the hip rather than by the Achilles tendon, allows the commercially more important muscles of the carcases to be stretched, thus improving tenderness. MLC trials show that for beef, correct hanging is more beneficial to meat tenderness than electrical stimulation.
 
Lamb carcase suspended by Achilles tendon and hip
  Source: MLC
  • Ageing (or maturation) – ageing occurs as enzymes present in the muscle break down proteins post-slaughter. Carcases are held in refrigerated storage for varying periods to improve tenderness. The rate of ageing varies by species and by cut. For example, beef forequarter and fillet cuts do not need the same maturation as hindquarter cuts, which can be anything between seven and 21 days.
 
Recommended minimum ageing times
 
  Species

Pork
Pork
Lamb
Steer/heifer beef
Young bull beef 		Cut

Leg
Loin

High value cuts
High value cuts		 Days

4
7
7
7
14		 Further benefits up to days

-
12
10
21
21
 
Flavour
 
Flavour is the combined result of the taste and smell senses and, because it is a subjective property, is difficult to evaluate. Each species has its own characteristic flavour. Chemical reactions resulting in some 1,000 compounds during cooking contribute to the individual meat’s flavour.

The flavour of meat can be influenced by the diet of the animal. Grass or forage-fed cattle and sheep tend to produce meat with a more intense flavour than grain-fed animals. Grass-feeding increases certain polyunsaturated fatty acid concentrations in the muscle and improves flavour.

In the case of boar meat an unpleasant flavour can develop as the result of two compounds, androstenone and skatole, accumulating in the muscle tissue. This is known as ‘boar taint’ and is off-putting to some consumers. Good pig housing design and husbandry can help to control skatole, which is associated with the ingestion of faeces.
 
Colour
 
Colour is a major influence on the visual appeal of meat rather than on quality. The colour of meat is primarily dependant on the concentration and chemical state of the pigment myoglobin, which is responsible for moving oxygen through the muscle. In post mortem muscle that has not been exposed to air, myoglobin exists in its deoxygenated form which is a deep purple colour. On exposure to air, oxygen is held at the centre of the myoglobin molecule, giving rise to oxymyoglobin which gives meat its bright red colour. Finally, oxidation of the myoglobin to metmyoglobin occurs resulting in the brown colour of discoloured meat.

The amount of myoglobin varies widely between the three species, which accounts for the marked differences in colour between their meats. Myoglobin concentration usually increases with the age of the animal. Highly active muscles also have more myoglobin, for example loins.

The type of packaging used at retail and thus the amount of oxygen to which the meat is exposed, influences the meat’s colour and appeal to the customer (see Packaging section).

For more information:

Services, publication or websites

BPEX Chef’s guide to pork

BPEX Pork Cutting Manuals/Guides

BPEX Technical Services

EBLEX

HCC/Meat Promotion Wales

Click here to order a copy of MLC Shelf Life of Fresh Meat publication