Comparison of sponging and excising as sampling procedures for microbiological analysis of fresh beef-carcass tissue

Abstract

Sponging and excising were evaluated as sampling procedures for microbiological analysis of beef-carcass tissue. Brisket tissue portions (10 X 10 cm) were inoculated with 2 ml of an Escherichia coli ATCC 25922 cell suspension (3 x 108 CFU/ml). After 30 min, the portions were sampled by excising (EX) or swabbing (SP) with a sterile sponge and were analyzed for aerobic plate counts on tryptic soy agar and for total coliform counts and E. coli counts on Petrifilm E. coli count plates. Another set of inoculated samples was analyzed after being spray washed, in sequence, with water (6 s, 35°C, 3.4 bar), acetic acid (2%, 6 s, 35°C, 2.1 bar), water (20 s, 42°C, 20.7 bar), and acetic acid (2%, 6 s, 35°C, 2.1 bar). Additional samples were sampled for analysis after chilling at 7°C for 24 h. Bacterial counts recovered were influenced (P ≤ 0.05) by procedure of sampling (EX versus SP), time of sampling (0.5 versus 24 h), and by their interactions. Counts recovered 0.5 h after inoculation from unwashed or spray-washed samples were similar between the two sampling procedures (EX and SP). However, counts recovered after 24 h of sample storage were significantly (P ≤ 0.05) lower for the SP compared with the EX procedure. The results indicated that as the carcass tissue was stored, recovery of bacteria by SP was less efficient than was recovery by EX.