Comparison of Dehiding versus Scalding and Singeing: Effect on Temperature, pH and Meat Quality in Pigs

The aim of this work was to investigate the temperature and pH changes taking place at the slaughter line and during the chilling process, and the subsequent effect on meat and eating quality in pig carcasses that had either been scalded and singed or dehided. Both processes were followed by fast chilling. 219 halothane-gene-free Duroc Sire and Landrace-Yorkshire pigs were delivered from three farms and slaughtered over 2 weeks at either a dehiding or a scalding singeing slaughterhouse. Temperature and pH were measured at intervals from exsanguination until 6 hours post mortem. Ultimate pH, internal reflection, drip loss and colour (Minolta) were measured the day after slaughter. Colour (JPCS scale) was evaluated after freezing and thawing, and eating quality was estimated on unaged and aged (4 days at 4°C) m. longissimus dorsi (LD), using a trained taste panel. At the slaughter line the dehided carcasses had an almost constant and lower temperature compared to the scalded and singed carcasses. During chilling there is a shift in temperature curves between treatments, where the scalded carcasses had the lowest muscle temperature in LD and m. biceps femoris (BF) from 2hr post mortem and throughout the measuring period. In spite of the shift in temperature, the dehided carcasses had the highest pH in LD and BF from exsanguination and throughout the measuring period. The rate of pH fall in LD and BF was slowest in the dehided carcasses from exsanguination until 3 and 2hr respectively, post mortem. Dehided carcasses showed a 40% lower drip loss, a darker meat colour and a lower internal reflection in LD and BF compared to scalded and singed carcasses, thus indicating less protein denaturation in dehided carcasses. Scalding and singeing, however, lead to increased tenderness compared to dehiding, and this difference persisted even after ageing for 4 days at 4°C. The differences in toughness may be caused by increased proteolysis by released lysosomal cathepsins.