Distribution and evolution of bacteria on lamb carcasses during aerobic storage

Abstract

The change of bacterial counts during storage life of chilled (3±1 °C) lamb carcasses was determined by sampling at 0, 5, 10, and 15 d postslaughter and at the spoilage time. Three sites (neck, brisket, and leg) of each carcass were sampled using three sampling methods (swabbing, scraping, and excision of the swabbed and scraped areas). After slaughter, mean count of mesophiles (30°C) was 4.96 log10 CFU/cm2. The initial mean count of psychrotrophs (7°C) expressed as a percentage of the mean count of mesophiles was 33.4%. The mean values of mesophiles and psychrotrophs associated with spoilage were 7.4 log10/cm2 and 7.95 log10/cm2, respectively. Carcasses always had pH values above 5.8 and kept unspoiled 23-29 d. Brisket and leg were the most contaminated areas. Percentages of bacteria recovered by scraping were higher than those obtained by swabbing (ca. 20%). Bacterial counts were significantly affected by day of storage (p<0.001), sampling point (p<0.001), and temperature of incubation (p<0.05). Interaction between sampling day and sampling site was also observed.