Microbial Counts on Surfaces of Lamb Carcasses and Shelf-Life of Refrigerated Ground Lamb

Abstract

Aerobic plate counts (APC) and counts on psychrotrophs, coliforms, Staphylococcus aureus and molds plus yeasts were made from the surface of fresh lamb carcasses and in ground lamb during refrigerated storage in Baghdad, Iraq. The average surface counts of carcasses sampled weekly over a 16-wk period were 1.1 × 106/cm2 and 2.6 × 104/cm2 for APC and psychrotrophs, respectively. The average ground lamb counts sampled weekly over a 5-wk period were 3.1 × 105/g and 1.2 × 105/g for APC and psychrotrophs, respectively. The average coliform, S. aureus and yeast plus mold counts were all between 103 and 104 CFU per cm2 or g for carcasses and ground lamb, respectively, on the day of slaughtering. Upon storage of the ground lamb at 2, 4, 5 and 6°C, both APC and psychrotroph counts increased to 109 CFU/g within 1 wk with more rapid microbial growth as the storage temperature increased from 2 to 6°C. Organoleptic spoilage was first detected when APC reached 109 CFU/g, or about 6 d at 5 to 6°C. The fat content of the ground lamb did not appreciably affect the APC and psychrotroph counts. Of 50 isolates of S. aureus, 48 were coagulase-positive.