212 Meat refrigeration Table 10.3 Storage life and nature of spoilage of vacuum-packaged pork 5°C Storage life Spoilage Storage life (weeks) characteristics characteristics 5.4-5.8 -4 Flavour changes. souring 6.2-6.5 Variable Greening, odour of His, putrefaction Source: Egan et al. 1986. with 12 weeks for normal pH beef (Gill and Penney, 1986). In metalized polyester or aluminium foil laminate vacuum packs, times were 9 and 15 weeks respectively. At a lower temperature Jeremiah et al.(1995a, b) have shown that off-flavour development, coinciding with lactic acid bacteria reaching maximum numbers, currently restricts the storage life of carbon dioxide CO)or vacuum-packaged pork at-15C to 9 weeks. Based on appear ance, CO2-packaged and vacuum-packed pork loin had storage lifes of ove 15 weeks and slightly over 12 weeks, respectively. Only small differences were found between pork loins from dark, firm, dry(DFD): pale, soft exuding(PSE)and normal quality groups. They believed that reducing the current levels of microbial contamination would allow storage life to be extended to meet all domestic and export requirements. Bell et al. (1996) detected no major off odours after 98 days at -01C from hot-boned bull beef that had been cooled and stored in vacuum or CO2 packs. On opening, the appearance of the strip loins was also acceptable. However, overageing as believed to have reduced the retail display life of the meat. The authors thought that the process could produce high quality beef for catering use with a storage life of 70 days. The effect of temperature and packaging was clearly demonstrated by Lee et al.(1985) and Gill and Harrison(1989). Only small changes in micro- bial numbers(Fig. 10.3), pH, drip and off-odour were found in vacuum or vacuum plus gas flushed packs of pork after 49 days storage at-4C ( Lee et aL., 1985), whilst green discolouration was significant after 14 days at 3 and 7C and 28 days at 0C. The amount of drip loss increased substan- tially with both length and temperature of storage(Fig. 10.4). Drip loss from pork liver tends to be higher than that from muscle and increases more rapidly during storage. At a storage temperature of 5C losses increased from 1.9% after 1 day to ca. 6%after 6 days( Strange et al., 1985) Gill and Harrison(1989)found that vacuum-packed cuts of pork longis- simus dorsi muscle( skin on) were grossly spoiled by Brochothrix thermo- sphacta after 2 weeks storage at 3C compared with 5 weeks at-15C. Cutswith 12 weeks for normal pH beef (Gill and Penney, 1986). In metalized polyester or aluminium foil laminate vacuum packs, times were 9 and 15 weeks respectively. At a lower temperature Jeremiah et al. (1995a, b) have shown that off-flavour development, coinciding with lactic acid bacteria reaching maximum numbers, currently restricts the storage life of carbon dioxide (CO2) or vacuum-packaged pork at -1.5 °C to 9 weeks. Based on appear￾ance, CO2-packaged and vacuum-packed pork loin had storage lifes of over 15 weeks and slightly over 12 weeks, respectively. Only small differences were found between pork loins from dark, firm, dry (DFD); pale, soft, exuding (PSE) and normal quality groups. They believed that reducing the current levels of microbial contamination would allow storage life to be extended to meet all domestic and export requirements. Bell et al. (1996) detected no major off odours after 98 days at -0.1 °C from hot-boned bull beef that had been cooled and stored in vacuum or CO2 packs. On opening, the appearance of the strip loins was also acceptable. However, overageing was believed to have reduced the retail display life of the meat. The authors thought that the process could produce high quality beef for catering use with a storage life of 70 days. The effect of temperature and packaging was clearly demonstrated by Lee et al. (1985) and Gill and Harrison (1989). Only small changes in micro￾bial numbers (Fig. 10.3), pH, drip and off-odour were found in vacuum or vacuum plus gas flushed packs of pork after 49 days storage at -4 °C (Lee et al., 1985), whilst green discolouration was significant after 14 days at 3 and 7 °C and 28 days at 0 °C. The amount of drip loss increased substan￾tially with both length and temperature of storage (Fig. 10.4). Drip loss from pork liver tends to be higher than that from muscle and increases more rapidly during storage. At a storage temperature of 5°C losses increased from 1.9% after 1 day to ca. 6% after 6 days (Strange et al., 1985). Gill and Harrison (1989) found that vacuum-packed cuts of pork longis￾simus dorsi muscle (skin on) were grossly spoiled by Brochothrix thermo￾sphacta after 2 weeks storage at 3 °C compared with 5 weeks at -1.5 °C. Cuts 212 Meat refrigeration Table 10.3 Storage life and nature of spoilage of vacuum-packaged pork Meat pH 0 °C 5 °C Storage life Spoilage Storage life Spoilage (weeks) characteristics (weeks) characteristics 5.4–5.8 6 Flavour changes, 3–4 Flavour changes, souring souring 6.2–6.5 4–5 Variable 2–3 Greening, odour of H2S, putrefaction Source: Egan et al., 1986