Postmortem changes in muscle electrical properties of bovine M. longissimus dorsi and their relationship to meat quality attributes and pH fall.

Heifers (n=47) were slaughtered and hung conventionally in an industrial meat plant. Electrical impedance (Py) and conductivity (EC) were studied for their ability to indicate or predict selected meat quality attributes i.e. Warner-Bratzler shear force (WBSF), sensory tenderness, texture, flavour and acceptability, water holding capacity (WHC) and colour. pH, electrical impedance (meat check) and electrical conductivity (pork quality meter) measurements were taken at hourly intervals up to 8 h and again at 1 and 2 days postmortem. Electrical measurements were taken again at 7 and 14 days postmortem. Freshly cut steaks (2.5 cm thick) were taken from the longissimus dorsi (LD) muscle at 2, 7 and 14 days postmortem, vacuum-packaged in plastic bags and stored at -20°C for WBSF and sensory analysis. Freshly cut steaks were used for WHC and colour measurements. During the development of rigor and over the ageing period, electrical changes occur in muscle tissue. Electrical measurements were found to change significantly between 1 and 14 days postmortem and when measured over the ageing period (at 2, 7 and 14 days postmortem) were significantly correlated to WBSF, sensory tenderness and Hunter 'a' and 'b' values (r=±0.56-±0.68, p<0.001) and weakly to moderately correlated to other sensory attributes (r=±0.31-0.58, p<0.001) measured at the same times postmortem; thus showing potential for these rapid physical measurements as indicators of meat quality if both electrical measurements and quality attributes are measured at the same times postmortem and correlations are calculated over the ageing period. However, electrical measurements taken at specific times at the early postmortem period (i.e. at 1 or 2 days) showed only a few weak relationships with meat quality attributes measured at later times postmortem (i.e. 7 or 14 days) demonstrating that early postmortem electrical measurements are not suitable for the prediction of ultimate meat quality. Py values taken between 7 h and 7 days postmortem were significantly correlated with all pH measurements with the exception of 1 day values. Two day Py measurements showed the highest correlations (r=0.45-0.62, p<0.01-0.001) with pH. EC was also found to be moderately correlated with pH although correlations were slightly lower than those obtained for Py. Highest correlations (r=0.47-0.59, p<0.01) were obtained for 7 h values.