Physical characteristics of lamb primals packaged under vacuum or modified atmospheres

Lamb primals (shoulders) were packaged under vacuum, 80% O-2/20% CO2, 50% CO2/50% N-2 or 100% CO2 and stored at 5 or 0 degrees C. Pack contents were examined at 7 day intervals to determine the composition of the pack atmosphere, drip loss, colour (muscle and fat) and pH (surface and internal). The composition of the gas atmospheres changed very little during storage. The only significant differences between developed head space compositions above primals stored at the two different temperatures (5 and 0 degrees C) were noted in packs stored for 28 days under 80% O-2/20% CO2. Low levels of drip loss (< 0.5%) were noted in all packs stored under the modified gas atmospheres. In contrast, significantly higher levels of drip loss (0.5-1.1%) were noted in vacuum packaged lamb stored at 5 and 0 degrees C. Acceptable muscle colour was observed 2 hr after opening of all packs. The only significant differences between atmospheres for lean muscle colour were noted after 28 days storage. Fat colour did not generally change during storage in any of the atmospheres, apart from a slight bleaching effect at 7 days. There were no significant differences between the surface or internal pH values noted after storage under any of the atmosphere/temperature combinations. In general, higher pH values were observed at the surface of the meat than in the interior. This pattern was noted before and after storage.