Greening of vacuum-packaged lamb – causative factors

Summary

​Australian vacuum-packaged lamb has at times been rejected for greening of packs after storage times as short as 6 weeks. Greening of beef was in the past associated with high-pH meat, so a multi-pronged program was developed to determine the main factors involved in the greening of lamb.A survey was conducted to determine the incidence of high-pH lamb;A storage trial was undertaken using lamb cuts of different pH ranges, andLamb cuts from carcases of different pH ranges were inoculated with a micro-organism expected to cause greening and packed in films of different oxygen transmission rate and stored at -1 and 2°C for up to 12 weeks.
Lamb knuckles and blades have a higher pH than the rack and also higher incidence of high pH. Over 97% of knuckles and blades had a pH above 5.7, whereas 64% of racks were above pH 5.7. Breed was the major factor influencing ultimate pH with full-blood Merinos being higher than mixed and other breeds.
The results of both the storage trial and the inoculation trial indicated that the main determining factor in preventing greening is temperature control. Storage of chilled vacuum-packed lamb at a temperature of -1°C or below will prevent greening and enable a storage life of 9 weeks or more.