28 Meat Grading and Cutting

28.1 Principles of grading

• The purpose of meat grading is to describe the value of a carcass in clearly defined terms useful to the meat industry.
  
• Both the buyer and the seller need an impartial third party to grade the carcass.
• If the buyer and the seller have their own system of payment for high and for low value carcasses, they can save time or money by not having the carcass graded.
• Grading facilitates long distance transactions and contracts for future shipments in which one or both parties have not yet examined the carcasses.
• Three major factors determine the value of a carcass relative to market conditions, (1) carcass weight, (2) the cutability or yield of salable meat, and (3) the quality of the lean meat.
  
• All three factors are continuous variables  measured in either absolute terms, such as weight, or in relative terms, such as those used by a taste panel.
  
• In scientific experiments, accurate carcass evaluation is necessary to search for minor differences between carcasses. But a less accurate system is adequate for commercial transactions, and the continuous spectrum of carcass properties is subdivided into a relatively small number of grades in a step‑wise sequence.
  
• Thus carcasses  placed in the same grade may exhibit small differences, but carcasses  placed into different grades should exhibit much larger, and commercially significant differences.
• The important grading systems are for beef, pork and poultry. Systems exist for the other species but they are mostly ignored or used in a very simple way. 

28.2 Beef grading

YOUTHFUL CHARACTERISTICS  (CATTLE LESS THAN  ABOUT TWO YEARS)

1. Cartilaginous caps on the first few thoracic vertebrae not more than half ossified.

2. First few lumbar vertebrae with evidence of cartilage or a red line on the neural  spinous process tip.

3. Neural  process is red and porous spinous when split.

4. Medial view shows ribs are narrow, round, and red.

5. The sternebrae are not fused.

MATURE  CHARACTERISTICS (CATTLE MORE THAN ABOUT TWO YEARS)

1. Thoracic caps more than half ossified.

2. No cartilage or red line on lumbar vertebrae.

3. Hard, white, flinty neural processes when split.

4. Wide, flat, white ribs.

5. Ossified sternum.

• The neural process is dorsal to the neural arch protecting the spinal cord. It is where the two sides of the arch join together. Other names are dorsal process and spinous process.
• Age estimates can only be approximate because, firstly, small- and large-framed cattle mature at different rates.  Secondly, the characteristics given above are subjective.

FEATURES OFTEN USED TO ESTIMATE MEAT YIELD

(1) An estimate of  subcutaneous fat thickness, usually made where the Longissimus dorsi is exposed.

(2) An estimate of the visceral fat remaining on the carcass,

(3) An estimate of the cross sectional area of the Longissimus dorsi muscle at the separation of the forequarter and the hindquarter.

(4) Hot carcass weight, or an estimate made from the cold carcass weight (cold weight x 1.02).

FEATURES REQUIRED FOR HIGH-QUALITY MEAT

(1) A check the fat is not too yellow.

(2) A check the muscles are not too dark.

• Acceptable fat colour varies geographically.  Consumers can detect the carotene content of fat, which is usually coupled with a diterpenoid taste in the lean (both from forage-fed animals).  Some consumers like this taste (I do!), others do not. When grain fed animals dominate the market, grading systems typically down grade beef with yellow fat. Why? Because, historically, consumers in these areas associate yellow fat with meat from old cows. When the rich countries run out of oil, and cattle once again are valued as self-mobile, self-feeding meat producers - I suspect white fat will be quietly dropped as a requirement for top grade beef.
  
• Down-grading dark meat is far more reasonable. Remember dark-cutting beef in lecture 14?
  
• Having graded the beef carcass, it usually stamped with a hammer or roller coated with edible dye. Thus, the cautious consumer usually gets to see some or all of the stamp on the fat covering a joint of meat.  The grade stamp usually has a numerical code to identify the plant of origin.
  

28.3 Pork grading

• Pork grading tends to be far less concerned with meat quality, and often simply becomes a feed-back system for rewarding producers of lean carcasses at an optimum weight. In some countries all pork is regarded as equal in quality - a foolish mistake in the long-term. In other countries, a serious effort may be made to probe pork carcasses to check their meat quality - primarily to reject PSE pork and give a premium for marbling fat.
• A advantage in grading pork is the skin often remains on the carcass until the day after slaughter.  This gives the fat a well-defined outer boundary, and fat depth probes may be used to automate data collection on fat depth.
• The probe pushes into the carcass and an optical diode detects the depth of the boundary between fat and lean.
• Some probes check for PSE and marbling in the muscle.
• However, ultrasonic methods can make multiple measurements as a pork carcass is pulled through a U-shaped frame - thus giving a superior estimate of subcutaneous fat depth.
• Thus, at present, some countries use an optical probe at one point while other countries use ultrasonics.

28.4 Poultry grading

• The primary decision in poultry grading is based on weight and animal age.
• Broiler or fryer chickens are typically up to 8 weeks in age, weighing 0.8 to 1.8 kg.
• Roaster chickens are typically older, weighing over 1.8 kg.
• Comparable separations are made for turkeys, ducks and geese, with the younger, smaller birds obtaining a premium (they are more expensive to produce per kilogram - but they are very tender and can be cooked rapidly).
• Poultry with tender meat are typically identified by their soft, pliable and smooth‑textured skin, and by their flexible sternal cartilages.
  
• The classes of poultry with meat of an intermediate level of tenderness are identified by their greater age, coarse skin, and less flexible sternal cartilage.
  
• The mature classes of poultry requiring prolonged cooking are the rooster, mature hen chickens, mature hen or tom turkeys, mature duck and mature goose. These classes have tough meat, coarse skin, and stiff sternal cartilages
• In chickens, young birds have unwrinkled combs with sharp points. In older birds, the comb becomes wrinkled with blunt points.
• Young ducks have soft bills, while older ducks have hard bills.
• Plumage becomes worn and faded in older birds (unless they have just molted).
• With age, subcutaneous fat becomes darker and becomes lumpy under the main feather tracts.
• With age, the pelvic bones become less pliable.
• With age, scales become larger, rough and slightly raised.
• In old birds, the oil sac becomes enlarged and sometimes hardened.
• With age, male chickens and turkeys may develop long spurs.
• With age, the cartilaginous rings of the trachea become stiff in ducks and geese.

28.5 Recognition of cuts of meat

Without taking a course in meat cutting, the most we can hope for here is for students to recognize where a meat cut originates in the carcass.

• Meat cutting is as variable as language. Sirloin steaks may be Longissimus lumborum in England (left side of diagram above), or Gluteus medius in North America (right side of diagram above). You only need to learn the cuts where you live!
  
•  Steaks and chops along the vertebral column usually command a premium price based on tenderness. Cuts through the proximal limb regions are intermediate in price. Finally, cuts from the neck and distal limbs are lest expensive.
• The recognition of the species of meat when cuts of beef, pork and lamb are displayed for sale as top‑quality fresh meat is based on the colour of the lean and on the size of whole muscles and bones. Beef lean has the deepest colour, and pork has the lightest colour. Lamb and veal are intermediate, depending on the age of the animal. Veal from entirely milk‑fed calves is extremely pale.
• If marbling fat is present as wavy lines and dots of white fat in the lean, it is very conspicuous against the dark color of the lean in beef, but is sometimes less visible in pork.
  
• Pork exhibits the greatest variation in depth of colour between different muscles.
  
• Pork often has the whitest fat, and beneath the subcutaneous fat may be seen the thick cutaneous muscles of the pork carcass. Some pork cuts retain their skin.

• To identify a cut of meat, first decide whether an unidentified cut is from the left or right side of the carcass.  Then ascertain its position and orientation in the carcass. Do not forget that left and right sides of the carcass form mirror images, and the two flat surfaces of a chop or steak from one side of the carcass may also form mirror images. This is particularly important when identifying muscles from diagrams.
• Examine the surfaces of the cut of meat, and look for a medial surface, as indicated by vertebrae, sternum, pubis, ribs, adductor muscle, gracilis, etc.
  
• Surfaces once part of the lateral surface of the carcass usually bear traces of trimmed or untrimmed subcutaneous fat, often with a grade stamp.
  
• The orientation of a cut of meat may be indicated by the extent to which the cut of meat is tapered. The abdomen is narrower than the thorax in an eviscerated carcass, and the limbs are tapered from proximal to distal. The dorsal spines of most of the thoracic vertebrae project posteriorly. The anterior ribs are shorter than the posterior ribs.

1. Look for a series of exposed blocks of porous bone. If a deep groove (neural canal) runs through the series, the bones are vertebrae from along the animal's backbone. If no groove is present, the bones may be part of the sternum. However, if a carcass has been poorly split into sides, the midline cut may miss the neural canal.
2. Look for rounded cross sections of bone from a limb, but remember part of the shaft of the ilium also is round in cross section.
   
3. The whole hindlimb is rounded in cross section, but the forelimb is flattened because it is located against the rib cage.
   
4. When the ilium has a rounded cross section in a whole sirloin, the muscle mass is lop‑sided, and there is some trace of the sacrum on the edge of the cut of meat. The more posterior part of the shaft of the ilium is triangular in cross section.
   
5. When the femur has a rounded cross section in the round, ham or hind leg, it is almost in the center of a circle of meat.
   
6. When the humerus or the shaft of the scapula have a rounded cross section in the chuck or arm region, it is alongside a series of transected ribs, and the muscle mass of the limb is oval in cross section.
7. Look for a section that has been cut through a flat bone. If rigidly part of the body of a vertebra, and if it is narrow, it may be a wing‑like transverse process of a lumbar vertebra from the loin. If it is rigidly part of a vertebra and is dorsal to the neural canal, and if it is one of a series of wide porous sections of bone, it may be a dorsal spine of a thoracic vertebra from the blade or rib region of the carcass. If it is curved and if it is movably jointed to a vertebra, it is probably the dorsal part of a rib. If it is parallel to a vertebral process, or if it is joined by cartilage to a vertebra, it may be the flat part of the ilium from the sirloin.
8.  If it is isolated by itself in the meat, or if it is shaped like a letter T, it is probably the scapula.
9. If there are no bones in the cut of meat, and if it is a flat slab of meat composed of several layers of flat muscles, it is probably part of the flank or abdominal wall.
10. If the cut of meat has large vertebrae with a complex shape, and if the outer surface of the meat is dark and ragged, the meat is probably from the neck.
11. If the outer surface of the cut of meat contains a flat rounded area of bone with a dimpled surface and traces of dried cartilage, the bone is the pubis from the rump region.
12. Look for a hole in the meat where the carcass might have been suspended from a large hook or gambrel. This indicates a hind leg, or the heel of the round in beef. In beef, the achilles tendon is hard, dry, pale yellow in color, and extremely strong
13. Look for a series of parallel ribs. The anterior ribs are shorter than the posterior ribs, and anterior ribs connect directly to the sternum.
14. Look for a long flap of muscle that runs diagonally over the medial surfaces of the ribs. This flap of muscle is the diaphragm. The ventral part of the diaphragm is anterior to the posterior part. In the beef carcass, the anterior part of the diaphragm appears in the plate, and the posterior part of the diaphragm appears at the start of the loin.
15. Look for a ball and socket joint. The socket of the scapula in the chuck region of the carcass is wide and shallow. The socket that forms the acetabulum of the pelvis is narrow and deep, and there may be a trace of the ligament which holds the head of the femur into the socket. In pork and lamb, the acetabulum may be contained in the top of the ham or leg.
16. Look for a small loose bone that would fill a cupped hand. This is the patella of the hind limb.
17. Look for the stump of the tail, with its small, simple caudal vertebrae.
18. Look for a series of small round sections of white cartilages. These are the costal cartilages from the plate, flank, belly or breast.
19. Look for groups of several small muscles, each surrounded by white fibrous tissue. These are the extensor and flexor muscles from the distal part of a limb. The Achilles tendon indicates the hind limb.

Further information