4 February 1997 Lincoln scientists at work on the 'tough-as-old-boots' problem

Scientists at Lincoln University, New Zealand, are getting their teeth into the meat tenderness issue, and with the meat industry so pivotally placed in the country's economy as a foreign exchange earner it’s important work.

"Tenderness is often the most variable and least obvious of the meat quality characteristics apparent before eating," says biochemist Dr Roy Bickerstaffe, of the University's Meat Quality Research Group.

"Things like colour, odour and juiciness can all be assessed before you take that first bite and imperfections perhaps tolerated, but when the meat hits your mouth and it's tough, there's bound to be dissatisfaction."

It is a big issue because as with all the ‘sensory characteristics’ of meat it's difficult to breed for traits which can only be accurately assessed after an animal has been slaughtered and consequently is no longer available for future breeding.

There is, however, assured money resting in the answer because once you know precisely what makes meat tough you can do something about working towards a product that's always tender, and that's what the customers want.

Research at Lincoln is focused on a better understanding of the process by which two protein-degrading enzymes called calpains break down specific meat proteins in the days following an animal's slaughter and so tenderise meat.

The group is working with individual farmers and breeders so that samples can be obtained from a broad cross section of meat animals in Canterbury with a representation of on-farm management conditions that may affect the quality of meat.

It has long been recognised that meat undergoes changes in quality after an animal is slaughtered. Hence carcasses are traditionally hung for up to three weeks to allow them to ‘age’ by the process of post-mortem tenderisation.

Although the precise biochemistry of what happens during this tenderisation process is poorly understood, the key role of one group of protein-degrading enzymes or proteases is clearly recognised. These are the calcium dependent calpains.

The enzymic action of calpains is regulated by, among other things, a specific inhibitor, calpastatin. Research in the United States suggests that in beef the level of calpastatin in the muscle at death is the most important component of the calpain-calpastatin system in determining ultimate meat tenderness.

Lincoln University work with sheep supports this view.

The Meat Quality Research Group's investigations have also demonstrated the existence of inherited polymorphisms in the calpastatin gene of sheep. Early results suggest that these alleles are linked to variations in meat quality. If this linkage is confirmed and the alleles sequenced, the Lincoln group is confident it will be able to develop rapid, low cost tests to predict an animal's meat quality potential.

Dr Barry Palmer says the group feels its research has a number of potential applications for increasing efficiency and quality within the meat industry.

"Firstly, we are developing a computer model of the meat tenderisation process in collaboration with a French based scientist, Dr Eric Dransfield, who is working in the same field.

"This computer model will ultimately predict meat tenderness from a limited number of biochemical parameters which can be determined from samples taken from carcasses on the processing chain. This information could be used to optimise carcass aging conditions, reducing the amount of cold storage space needed for meat processing plants and allowing them to produce a more consistent product.

"Secondly, molecular tests that predict potential meat quality could be used to select animals in breeding programmes without the need to slaughter them to test their meat quality characteristics or to gain information prior to slaughter in order to use appropriate killing and aging conditions to ensure the highest possible meat quality results or to tailor their quality specifications according to market destination.

"Thirdly, utilising our knowledge of the calpain-calpastatin connection, genetic manipulation could be used to produce animals that have the 'right' muscle biochemistry so they produce meat of optimal tenderness."

Groups involved in meat quality research in the United States and France have taken a close interest in the Lincoln work.

"There is an eagerness by world authorities to see what we're doing here in New Zealand," says Dr Bickerstaffe "and collaboration and dialogue with overseas groups will continue."

Ultimately, of course, it all comes down to the steak or chop on your dinner plate and as Canterbury beef producer Brent Rawstron of Rossendale Beef has commented, if the New Zealand meat industry can eventually take on board the results of the research now being carried out here and abroad, the country will be well placed to compete as never before in international meat markets.