The development of meat tenderness is likely to be compartmentalised by ultimate pH

Bull Musculus longissimus dorsi (n = 63) were categorised into high (pH >= 62), intermediate (pH 5.8-6.19) and low (<= 5.79) ultimate pH (pH(u)) and aged up to 28 days postmortem at -1 degrees C. High pH(u) samples were acceptably tender at 1 day post mortem and significantly more tender than low pH(u), meat at all ageing timepoints (p < 0.05). Rapid autolysis of mu-calpain in high pH(u) meat was linked with the more rapid degradation of titin, nebulin and filamin in this pH(u) group. Desmin degraded faster in low pH(u) meat and was concurrent with an increase of cathepsin B levels. The results from this study support the hypothesis that beef tenderisation is pH(u) compartmentalised with tenderness in high and low pH(u) meat characterised by variable rate of degradation of high and low molecular weight myofibrillar proteins during ageing, which are in turn regulated by mu-calpain and cathepsin B activities. (C) 2013 Elsevier Ltd. All rights reserved.