Purpose: To examine the effectiveness of several sampling methods for the recovery of microbial indicators in beef trim.
Methods: Fifteen samples of beef trimmings were collected from an establishment using the N60 technique under federal inspection. Each sample was subjected to multiple sequential sampling methods including swabbing, rinsing, and grinding of the same trim sample divided among the sampling methods. A 100 cm2 of beef trimming was swabbed three sequential times with sterile sponges pre-hydrated buffered peptone water (BPW). 25g of beef trimmings were rinsed three times sequentially in BPW. Finally, 25g of trimmings was ground and the ground meat was rinsed three times in BPW. Appropriate serial dilutions were plated onto aerobic plate count and E. coli petrifilms and incubated at 36°C±1 for 24 and 48 hours.
Results: Generic E. coli counts were below the detection limit (<10CFU/ml) for all of the sampling methods and samples. The aerobic bacterial counts obtained from the first enumeration of swabbing, rinsing and grinding were 1.9 logCFU/100 cm2, 2.9logCFU/g and 3.0logCFU/g, respectively. The total aerobic bacteria recovery using swabbing, rinsing, and grinding were 2.3logCFU/100cm2, 3.0logCFU/g, and 3.1logCFU/g, respectively. Swabbing was significantly lower than rinsing and grinding (P<0.05) for both the first or total bacterial recovery. However, the total coliform recovery using rinsing was not significantly different (P<0.05) from either swabbing or grinding, but swabbing recovered the least. Simple linear regression showed a moderate correlation of 0.74 and 0.64r2 for swabbing vs rinsing and rinsing vs grinding methods, respectively.
Significance: The efficacy of the sampling method used is critical in evaluating the microbiological quality of beef trimmings to improve public health.