The intracellular distribution of small heat shock proteins in post-mortem beef is determined by ultimate pH

This study analysed Longissimus dorsi muscles from 39 Angus or Angus×Limousin bulls to determine the small heat shock protein (sHSP) dynamics in beef aged at 15°C. Using quantitative ELISA we determined that alpha β-crystallin and HSP20 were present at higher levels in muscles from Angus bulls. sHSP levels peaked at 0.5 and 3h post-mortem for HSP20 and alpha β-crystallin respectively. Intermediate pH (pH 5.7-6.3) beef had the highest level of alpha β-crystallin expression at 3-6h post-mortem. Low pH (<5.7) meat had no detected soluble alpha β-crystallin and had diminished HSP27 at 22h post-mortem. The transition of sHSP between a soluble to an insoluble phase was demonstrated by pH titration of a sarcoplasmic fraction. The effect of ultimate pH upon sHSP distribution in post-mortem muscle may influence final meat quality characteristics.