Modification of in-pack conditions to extend the storage life of vacuum packaged lamb

High pH (>5·9) lamb loins from a research abattoir were subjected to differing packaging treatments to determine whether package modification could reliably extend the storage life of chilled lamb cuts beyond that attained by cuts vacuum-packaged in film of low gas permeability, as in current commercial practice. Treatments applied were carbon dioxide flushing or addition of a citrate buffer (pH 4·8), a 5% lactic acid solution or a Lactobacillus inoculum (plastic packs only) and packaging in a plastic film of moderately low oxygen permeability (140 cc/m(2)/24 h at 25°C and 90% relative humidity) or in a foil laminate of immeasurably low oxygen permeability. After 12 weeks' storage at -0.5°C, the cuts packaged in the plastic film were spoiled by off-odours produced by enterobacteria, except for inoculated cuts, which, instead, had developed unacceptable dairy flavours. In contrast, cuts packaged in foil laminate developed floras of lactobacilli that had not caused spoilage after 12 weeks, and meat colour was much improved by the exclusion of oxygen. Loin cuts from a commercial packaging operation were packaged in a shrinkable plastic film of low oxygen permeability (30 to 40 cc/m(2)/24 h at 25°C and 90% relative humidity), in foil laminate, or in foil laminate after the addition of 5% lactic acid solution. For the first 6 weeks, cuts were stored in a commercial chiller nominally operating at 0°C; subsequently, they were held in a laboratory chiller at -0.5°C. Some cuts packaged in the shrinkable plastic were spoiled after 9 weeks' storage and all were spoiled at 12 weeks, because of off-flavours produced by enterobacteria. All cuts packaged in the foil laminate were very acceptable at 9 weeks but most were spoiled by off-flavours at 12 weeks. Most cuts treated with lactic acid and packaged in foil laminate were unspoiled after 12 weeks. The packaging requirements indicated to be necessary for reliable extension of the storage life of vacuum packaged lamb are discussed.