The effect of the initial gas volume to meat weight ratio on the storage life of chilled beef packaged under carbon dioxide

Normal pH (5·5-5·7) and high pH (>6·0) beef cuts of 400 g were vacuum packaged in polyvinylidine chloride (PVDC) laminate, in aluminium foil laminate or in foil laminate with a CO(2) scavenger (Ba(OH)(2)); or were packaged under CO(2) in foil laminate with CO(2) added at 200, 400, 700, 1000 or 2000 ml per kg of meat. The process used to prepare meat before packaging resulted in an initial flora containing a high fraction of eneterobacteria but with undetectable numbers of lactobacilli. During storage at +1°C, all vacuum packaged meat developed floras containing substantial fractions of enterobacteria. The enterobacteria fractions were larger on high pH than on normal pH meat, and on normal pH meat in PVDC or in foil laminate plus CO(2) scavenger packs than on normal pH meat in foil laminate without the CO(2) scavenger. All vacuum packaged meat was spoiled by putrid flavours, high pH meat at 7 weeks and normal pH meat at 12 weeks. Increasing amounts of added CO(2) progressively retarded the development of putrid spoilage, as growth of the spoilage floras was slowed while the relative numbers of lactobacilli in the floras were enhanced. With the two largest amounts of added CO(2), spoilage was delayed until 15 weeks and 21 weeks for high pH meat and normal pH meat, respectively, and enterobacteria were detected in the spoilage floras only at later sampling times. With lesser amounts of added CO(2), enterobacteria persisted or re-emerged at earlier times, in the floras.