Effects of Electrical Stimulation and Early Postmortem Muscle Excision on pH Decline, Sarcomere Length and Color in...

Electrical stimulation of prerigor beef carcasses produced a rapid initial drop in pH of longissimus muscles excised and vacuum-packaged at 1, 2 or 4 h postmortem. This initial drop was further increased by delayed excision and was severe enough that even -30-C storage did not retard the overall decline. Through the first 10 h of the 30-h sampling period at -30 C, pH was higher for nonstimulated than for stimulated muscle and was substantially affected by the time of muscle excision. Compared to -30-C storage, a 3-C storage temperature resulted in an even faster decline of pH in electrically stimulated muscle but still hindered the decline in nonstimulated muscle. Although the decline in pH was affected by electrical stimulation, excision time and storage method, initial (time of excision) and final (5 days postmortem) sarcomere length were not. Electrical stimulation of prerigor beef carcasses did not affect the appearance of hot-boned or cold-boned longissimus or semimembranosus muscles. Excision time, however, did affect the color and color uniformity of semimembranosus muscles, apparently because of alteration of the temperature and pH relationship. Excision times of 1 or 2 h appear preferable to 4 or 48 h because combinations of high temperature and low pH within deeper areas of the carcass could cause severe non-uniformity of color in muscles set deep within the carcass.