The influence of season on quality characteristics of hot-boned beef m. longissimus thoracis

Samples of m. longissimus thoracis (LT) muscle were randomly collected from 70 Omani beef cattle 1 h after slaughter between August 2001 and July 2002 in the Muscat Municipality central slaughterhouse to investigate the effect of seasonal parameters on meat quality during the hot and cool seasons of Oman. The collection period (12 months) was divided into two seasons according to ambient temperatures and relative humidity and termed: Cool Season (November-March with average temperature of 21.2 ± 1.40 °C and 57.9 ± 1.61% relative humidity) and Hot Season (April-October with average temperature of 34.3 ± 1.67 °C and 48.8 ± 7.57% relative humidity). The season had a significant effect on meat quality characteristics of the LT muscle. Muscles collected during the hot season had significantly (P<0.001) higher ultimate pH values (6.24) with significantly (P<0.001) lower Warner-Bratzler (WB) shear force values (10.12) than those collected during the cool season (5.54 and 15.58). In these hot-boned samples, there was a linear relationship between ultimate pH and WB shear values. Cooking loss was significantly (P<0.001) higher for cool season samples (26.01%) than from hot season samples (19.75%). Beef from the hot season group had significantly (P<0.001) darker meat than that of the cold season group, based on L ^* (31.45 vs 35.58), a^* (18.53 vs 23.19) and b^* (4.16 vs 6.40) colour measurements. There was a linear relationship between ultimate pH and cooking loss, L^*, a ^* and b^*. These results indicated that heat stress (>30 °C) lead to physiological stress in beef cattle, which in turn increased muscle ultimate pH and influenced related meat quality characteristics.