The performances of two commercially available packaging systems for prolonging the shelf-life of fresh meat were compared at 1°C and during simulated retail display. Beef and pork loin steaks in modified atmosphere packs (MAP), containing 75% O2 and 25% C02, developed an initial bright red (beef) or pink (pork) colour, which gradually changed to brownish-red or -pink after 12 days; similar samples in vacuum skin packs (VSP) remained purple-red throughout the storage period. Off-odours developed more rapidly in MAP (8-12 days), possibly due to more extensive growth of Brochothrix thermosphacta and the effects of aerobic conditions on the metabolites of lactic acid bacteria, which predominated in both types of packs. Evidence of rancidity, using thiobarbituric acid assay, was demonstrated in MAP beef after approximately 8 days, but not in VSP. Drip losses in MAP increased after 6 days' storage, but remained generally low in VSP. Physical texture (shear force values of cooked samples) of beef was unaffected by packaging method, but pork in VSP was significantly more tender (P < 0.001) than in MAP. KeywordsModified atmosphere packaging, packaging of meat, vacuum skin packing.

Toughness of poultry breast muscle was influenced by the rate of rigor onset, the rate of cooling and chilled storage time. The pH of the breast muscle at 20 min after stunning (pHzo) in 52-day-old chickens varied from 5.9 to 6.9, and in 70-day-old turkeys from 6.2 to 6.8. In turkey meat with pHzO > 6.4, toughening was induced by immersion chilling to 7°C within 65 min post mortem and subsequent 'tanking' in iced water. Unaged, thawed meat from chicken carcasses, in which freezing commenced about 2 h after stunning was tougher than that from carcasses chilled for 16 h before freezing. Both were tender after 7 days chilled storage. Electrical stimulation of carcasses using 94 V decreased pH20 by an average of 0.3 unit in turkey, with no overall increase in tenderness. In chicken, it decreased the pHzO by 0.5 unit, but caused an overall toughening due to increased rigor shortening in carcasses with pH20 < 5.8.

Commercial crossbred pigs weighing about 80 kg and comprising equal numbers of females (gilts) and castrated males (castrates) were killed at a bacon factory 4 h (controls), 24 h or 48 h after food withdrawal. The carcasses from pigs fasted 24 h were on average 1-4 kg lighter, and those from pigs fasted 48 h, 2-9 kg lighter, than those of the control group. Fasting also reduced liver weight by about 0-3 kg but had no significant effect on backfat thickness or mean initial or ultimate pH in the muscles. Carcasses were cured into bacon by the Wiltshire process. Those from pigs fasted longer gained less weight after pumping with brine but also lost less weight during brine immersion and maturation. The overall yield of bacon, in relation to carcass weight, was therefore not affected by fasting. Consequently, the reduced carcass weight in the fasted pigs was carried through almost unchanged to the final yield of matured bacon. This was proportionately reduced by 0019 in the pigs fasted 24 h and 0043 in those fasted 48 h when compared with the control group.There was thus no evidence of any material reduction of yield differences during curing which could be caused by equilibriation of water in the carcass tissues with that in the curing brine. The implication is that losses in carcass weight in fasted pigs cannot be attributed simply to dehydration. Cured sides from fasted pigs tended to have proportionately slightly less weight in the ham and middle and more in the shoulder, and bacon from the pigs fasted 48 h was marginally less salty. 143