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Sharon Van Wyk
23 Oct 2009 06:00
The next time you place a prime piece of steak over hot coals, think about Dr Lorinda Frylinck and the meat science research team at the Agricultural Research Council (ARC) in Irene.
The main aim of this dedicated group of scientists and students is to make your steak as tender, juicy and flavoursome as possible.
They spend their days in the pursuit of the perfect prime cut.
The Red Meat Research and Development Trust and Thrip-funded beef tenderness model project that Frylinck and her colleagues are working on is aimed at improving the overall consistent quality of red meat.
‘Achieving consistent levels of high quality has been a problem in the meat industry for a long time,” says Frylinck. ‘We are working on ways to get South Africa’s meat to be as tender and as attractive as possible.”
Frylinck says that when it comes to meat quality, while genetics plays a supporting role in dictating the quality of beef that ends up on the butcher’s block, environment and diet take centre stage. Also influencing the quality is the pre-slaughter care of live animals and post-slaughter care of carcasses.
‘Traditionally, animals going for slaughter are transported well in advance and then placed in holding pens to rest them, helping them to recover from the stress of the transportation process. Food is withdrawn from the animals prior to slaughter, but the timing of this withdrawal has been shown to have an effect on the quality of the meat post-slaughter.”
The handling of carcasses also has a huge impact on the tenderness of meat, as do the various biological processes that take place following slaughter. The most important of these is rigor mortis. This occurs after death because of chemical reactions taking place within muscle tissues which cause the muscles to contract perpetually until certain enzymes begin to break down and soften them.
The onset of rigor mortis and its resolution is an important factor in meat tenderness, as is the rate at which the carcass is cooled following slaughter. If the post-slaughter meat is chilled too quickly to temperatures below 10°C when the pH is still greater than six with energy still available, a phenomenon known as cold shortening occurs, in which the muscle shrinks severely resulting in very tough meat.
Another phenomenon that occurs under less severe circumstances is cold toughening. In this case the enzymes responsible for the maturation of meat are inhibited as a result of lower temperatures.
To prevent cold shortening and cold toughening and to speed up the process of rigor mortis, carcasses are electrically stimulated following slaughter.
Frylinck says that cooling carcasses slowly prevents the need for electrical stimulation and it can have a more positive effect on the quality and appearance of meat if food safety can be guaranteed.
‘In the first phase of our project we determined the ‘ideal’ pre- and postslaughter conditions for South African crossbred beef breeds and compared meat tenderness of these breeds under typical commercial abattoir practices—chilling at 4°C within two hours of slaughter,” says Frylinck.
‘Variations in pre- and post-slaughter conditions operations have a great effect on the muscle energy status of the animal at point of slaughter. This has major effects on initial tenderness and prolonged ageing,” she says.
Frylinck heads the project’s extensive team of researchers, technicians and students, which is in the final phase of interpreting the data captured since the project began in 2004.
Frylinck says that while her team can fine-tune pre- and post-slaughter conditions, much still depends on the facilities at individual abattoirs. ‘Rural abattoirs, for example, often do not have the cold storage facilities that larger, urban-based abattoirs have,” she says.
Phase two of the project has examined the meat quality differences (colour of meat and subcutaneous fat, drip loss, water holding capacity, tenderness and other factors such as juiciness and aroma and the percentage of intramuscular and subcutaneous fat) of A-age (feedlot and veld) animals, AB-age (feedlot and veld) animals, and B-age (veld) animals under the determined ‘ideal” slaughter conditions for South African crossbred beef breeds.
‘Animals raised on the veld have more yellow fat,” says Frylinck. ‘Traditionally, yellow fat was thought to indicate that an animal was older, and therefore its meat tougher. However, our research has shown that the yellow fat found in young animals as a result of diet and environment is not an indication of toughness and therefore producers should not be penalised for that,” Frylinck says.
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