Online rigor test available for licensing.

Meat processors and food technologists are constantly searching for ways to remove a major cause of consumer dissatisfaction, namely variability in the texture of meat and the consequent toughness it causes. The largest source of variability in poultry texture arises from the different rates at which carcasses go into rigor. This depends on a number of factors, such as stress immediately prior to slaughter, genetic make-up, raising procedures and age.

Carcasses that go into rigor relatively slowly are liable to be toughened by cold shortening after cooling. Conversely, carcasses that go into rigor rapidly are liable to be toughened by hot (or rigor) shortening that occurs before cooling. Similar problems arise with pigs. A particular problem is that of drip: a pig carcass that goes into rigor rapidly suffers excessive drip and weight loss.

While these tendencies can be alleviated by slow cooling or by advancing the time of cooling, such measures can only be employed satisfactorily if the amount of rigor can be measured. Otherwise, a compromise process has to be employed, with carcasses that have gone into rigor faster or slower than the average.

A simple and rapid way to measure the onset of rigor in animal and bird carcasses would be of considerable value in the processing of chickens and pigs, and possibly ducks, turkeys or cattle. Scientists at the British Technology Group (BTG, 101 Newington Causeway, London SE1 6BU, England, U.K.) are looking to license an online rigor tester that uses the basic feature of rigor-that muscles so affected have a higher resistance to stretching than unaffected muscle tissue. The technique has been developed to measure stiffness in whole carcasses.

The process involves suspending the carcass, after it is bled, from a shackle attached to a force transducer. A jolt is applied to the shackle by allowing the carcass to drop a couple of inches (50 mm) and using the transducer to measure the time and nature of the ensuing oscillations. The frequency of the damped oscillations, which increases from about 7 Hz in pre-rigor carcasses to about 15 Hz in post-rigor carcasses, and the time taken for the first peak force of the oscillations to be generated are a function of the stiffness of the carcass. The transducer will indicate a varying force after the drop that will settle down within a couple of seconds and equate to the weight of the carcass.

Although stiffness in whole carcasses changes less than stiffness measured parallel to the muscle fibre, it is easily quantifiable. Damping, which decreases progressively with time after slaughter, affords an alternative measure of how much rigor has developed. Further information. Tim Addison; phone: [phone]; fax: [phone]; URL: www.btg.com.