Toughness in Meat

Meat exhibits toughness in a number of ways and how this is measured is important. In the laboratory there are mechanical means for measuring it but that figure may not correlate strongly with our own “measurement” as we chew. In fact, tough meat may be very acceptable to the consumer if it is succulent or has a relatively high fat content, or if it has been mechanically broken down. Thus, we never get tough meat at McDonalds.

The physical explanations for toughness in meat fall into three main areas:

1.      The ratio of connective tissue in the cut.

This is determined by the function of the muscle, the sex and the maturity of the animal.

2.      The time after slaughter that the meat is consumed.

Meat undergoes post-mortem changes whereby the autolytic enzymes begin to break down bonds between molecules. Ultimately, if we didn’t intervene, these enzymes are capable of liquefying most of the muscle tissue.

3.      The percentage of water in the muscle.

Perceived as “succulence” by the consumer this is perhaps the most significant contributor to toughness in pork. At slaughter lean meat contains about 75% water, well cooked meat 55% and pork jerky contains about 2% and is, of course, very tough.

Different muscles within the body have a different mix of tissue and even muscle fibre types depending on their function role. Those that are active in locomotion tend to have a higher ratio of “fast twitch” muscle fibres and connective tissue (collagen). Those that control posture do not need to be violently active and therefore there is a preponderance of ‘slow twitch” fibres and less connective tissue.

The meat cuts we know as the Scotch Fillet, Eye Fillet and Sirloin all fall into the latter category and are recognised as prime eating cuts.

In the former category are the Bolar and Blade Steak to name a few and these cuts are utilised by extensive cooking (which denatures the collagen)

Connective tissue tends to increase in ratio with age (probably as the muscle mass diminishes) or in the presence of testosterone inducing secondary male sexual characteristics.

Most pigs however are slaughtered at around 26 weeks of age so shrinking muscle mass and secondary sex changes have little impact on connective tissue ratios.

 Post-mortem

Immediately after death the cells of the body release powerful proteolytic and sacchrolytic enzymes that begin to break down the cell. Depending on the temperature of the carcass, these enzymes break down the collagen (complex poly-saccharide) and the quaternary and tertiary bonds in proteins.

This is the state we know as aging of meat. The challenge for the butcher is to keep the temperature high enough to facilitate quick aging, but at the same time to keep the temperature low enough to prevent bacterial growth (putrefaction).

 Water Holding

The producer has no need to worry about the connective tissue ratio as the pigs are slaughtered at a young age. Steers tend to be 18 months and upwards, heifers 14 months and upwards. Unfortunately there is little control over the age of the carcass post-mortem – carcass killed at Timaru at 2:30pm on a Monday could be broken into the retail cabinet of an Auckland supermarket by 9:00am on the Wednesday.

The whole supply does have immense control over the water holding capacity of the mean if they are only willing to exercise that control. The reason that they don’t is that they are rarely rewarded for eating quality – their returns based on what is effectively lean meat yield.

The market will always respond to financial incentive and in the late 80’s this is what the pork production sector did. Retailers were saying that consumers were becoming averse to visible fat and adjusted their payment schedules accordingly.

The less skilled (or less scrupulous) producers tended to starve their finishing animals to achieve the required fat depth, the better farmers sought solutions in diet and genetics.