Beef tenderness and sarcomere length

A wide range of muscle glycolytic rates was produced in 60 beef carcasses by applying different forms and periods of electrical stimulation immediately after decapitation; a further seven carcasses were not stimulated. The sides were subjected to normal chilling, and at 48 h one short loin per carcass was taken for tenderness evaluation and determination of sarcomere length (SL). In the 19 relatively slow-glycolysing loins-those of 3-h pH (pH(3)) above 6·3-tenderness extended over almost five panel units on a 1-8 scale, and included both the tenderest two and the toughest 10 muscles of the entire study. In the 48 loins of pH(3) below 6·3, on the other hand, tenderness ranged over only 2·5 units, and on average was a full panel unit higher than that of the high-pH(3) muscles. The most striking difference between the two groups, however, was in the relationship between toughness and shortening; the correlation of panel tenderness on SL was remarkably high in the slow glycolysers (r = 0·84), but negligible in those of faster pH decline (r = 0·16). Thus although shortening occurred to about the same extent and over the same range in both groups, it influenced tenderness and tenderness variability only when glycolysis was quite slow. A loin pH(3) of below 6·3, however, is unusual in non-stimulated carcasses, so slow glycolysis and the very wide tenderness diversity accompanying it must be expected in commercial operations that do not use electrical stimulation.