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  Meat Quality
 

 

What the customer wants

To the consumer, an enjoyable meat eating experience is one that associates meat with being tender, juicy and flavoursome. General

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 whether the customer decides to 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.

Other quality characteristics can be found from information on the label, such as the nutritional value, freshness and microbiological safety. But there are also other factors which can influence the acceptability of meat. These include elements such as animal welfare and the impact of production on the environment.

The key factors that affect meat quality in beef, lean and tender lamb and quality pork are:

 

·    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 or dark, firm and dry meat affecting both tenderness and flavour.

 

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 break down the collagen and thereby tenderise the meat.

 

General

 ·    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 as 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. Trials show that for beef, correct hanging is more beneficial to meat tenderness than electrical stimulation.

 

·    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

Cut

Days

Beneficial Extra Days

Pork

Leg

4

 

Pork

Loin

7

12

Lamb

 

7

10

Steer/heifer

High Value Cuts

7

21

Young Bull

High Value Cuts

14

21

 

Flavour

Flavour is the combined result of the taste and smell senses and, because we all smell and taste things differently, is difficult to evaluate or measure. General

Each species has its own characteristic flavour beef tastes different to pork which tastes different to lamb. Chemical reactions which take place during cooking result in some 1,000 different compounds being produced which 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.General

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 will also affect the amount of oxygen to which the meat is exposed and will therefore influence the meat’s colour and appeal to the customer.

 

Packaging

Packaging has two main functions: to protect and preserve the meat and to carry information about the product.

There are many packaging systems, and the choice of which to use will depend on many factors including cost, the volume of product being handled and presentation. Some of the main methods used in the meat industry are described below

Shelf life varies considerably depending on the packaging used. The precise shelf life will also depend on the condition of the meat when packed, storage conditions and the quality of the packaging materials, so the details given below are only guidelines.

 

Vacuum packing

Vacuum packing seals meat in plastic bags from which air has been expelled. The bags minimise both gas and moisture permeability; they act as a barrier to prevent both the meat surface coming into contact with external oxygen and the meat’s moisture from seeping out. The lack of oxygen inhibits the growth of bacteria which cause the meat to deteriorate.

Vacuum packed primal cuts stored at 0°C should have a shelf life of 4-8 weeks. Meat held in vacuum pack for long-term storage must be kept at a temperature of 3°C or less.

 

Overwrapping

The meat is displayed on expanded polystyrene trays under light gauge PVC film. This film is permeable to external air enabling oxygenation of the meat to take place so that the meat retains its red ‘fresh meat’ colour. However, further oxidisation soon takes place to change the colour to dull brown.

The shelf life of overwrapped meat is short, up to 3 days if stored at 0°C

 

Modified Atmosphere Packaging (MAP)

UPVC or expanded polystyrene packs are formed to produce trays from a web of plastic. The air from the pack is expelled and then the pack is flushed with a modified atmosphere that contains higher levels of oxygen and carbon dioxide. The meat is then sealed under a top web of laminated, low permeable barrier film. The higher concentration of oxygen preserves the red colour of the meat, while the presence of carbon dioxide inhibits the growth of bacteria.

If packs are kept at 0°C, they should have a shelf life of about one week.

 

Frozen meat

Frozen meat can be stored for much longer times depending upon the packaging. Freezing of prime cuts of meat can have negative affect on meat quality, but is largely neutral in its effect on minced/diced product. The quality of the meat will also deteriorate depending on the length of storage time of the frozen product and is why, in general, fresh meat is more expensive than a similar frozen product.