Eric Dransfield

Conditioning of meat from different species. Relationship between tenderising and the levels of cathepsin B, cathepsin L, calpain I, calpain II and β-glucuronidase

The conditioning times for beef, calf, lamb, pig and chicken M. pectoralis profundus were determined from extensibility measurements at 15°C. Extracts from the same muscle from these animals and also rabbit were assayed for free and total cathepsin activities using a new method to determine the extent of inhibition by cystatins. A new method was also developed for the rapid estimation of each calpain. The results show that pig muscle contained most cathepsin activity. Cathepsin L appeared to be inhibited to a greater degree than cathepsin B in the pig, rabbit and chicken muscle extracts. These extracts also contained proportionately more cathepsin L than the other species. Chicken muscle contained only a low level of the more sensitive neutral proteinase, calpain I. It was concluded that the rapid conditioning time for chicken muscle could not be explained in terms of either the free or total levels of cathepsins B and L, nor of the individual calpain activities.

Cold-shortening toughness in excised pork M. Longissimus dorsi.

Excised pork M. Longissimus dorsi from six Large White Cross pigs were subjected to a range of chilling rates using temperatures between 20°C and -20°C. Onset of rigor at 20°C varied from 3 to 7.5 h between animals and rigor was complete in 6.5 to 15 h. Cold-shortening was induced when samples were chilled in air or liquid at 3°C or below but not at 5°C or ambient. The highest cooling rate, using liquid at -1°C, reduced the meat samples to 10°C in about 1 h and induced 34% shortening. After ageing for 5 days at 3°C in 26 h. Considering all chilling rates, toughness increased as the time to reach 10°C decreased to 3 h or less. Extensive cold-toughening would be unlikely to occur in current UK commerce and any toughening which did occur would be confined to Longissimus dorsi M. in about 20% of carcasses. The projected increased introduction of very rapid cooling, particularly in conjunction with lean pig production and hot deboning of pork, could toughen all cuts in about 60% of carcasses.