THE EFFECTS OF SPRAY AND BLAST-CHILLING ON CARCASS SHRINKAGE AND PORK MUSCLE QUALITY

Combinations of blast- and spray-chilling of pork carcasses were compared to spray-chilling at conventional chilling temperatures with regard to carcass shrinkage during chilling and pork muscle quality. In experiment 1, pork sides were spray-chilled at 1-degrees-C for the first 10 h (40 spray cycles of 60-s duration every 15 min) of cooling or blast-chilled at -20-degrees-C for 1, 2 or 3 h followed by spray-chilling for 9, 8 or 7 h duration, respectively. All pork sides were then chilled to 24 h post mortem at 1-degrees-C. Experiment 2 followed the same procedures as experiment 1, except that -40-degrees-C was used as the blast-chill temperature. Carcass shrinkage was similar for all treatments in experiment 1 at 24 h ranging from 0.5-0.7 g 100 g-1. Blast/spray-chilling increased the rate of chilling and reduced the rate of post-mortem pH decline in two muscles (longissimus thoracis, LT and semimembranosus, SM) compared to the combined conventional/spray-chill treatment. Carcasses that were blast-chilled for 3 h had LT muscles that were darker with a higher protein solubility, less drip loss, shorter lengths and higher shear values compared to those from carcasses in the conventional/spray-chill treatment. In experiment 2, carcasses blast-chilled for 3 h at -40-degrees-C recorded a weight gain at 24 h of 0.4 g 100 g-1, compared to a weight loss in all other treatments (0.2-0.4 g 100 g-1). Muscle colour was darker in both the LT and SM of carcasses blast-chilled for 3 h at -40-degrees-C compared to carcasses from the conventional/spray-chill treatment, but most other measurements of muscle quality showed an inconsistent response to chilling treatment.