Comparison of swabbing, rinsing, and grinding as sampling methods for the recovery of indicator microorganisms on beef trimmings
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Meat is a highly perishable product and can become unfit for consumption in a short period of time if not properly handled. It can also be hazardous to public health due to pathogen presence. Much progress has been made in the beef processing industry over the past several years to monitor process control to ensure that food safety and quality hazards are minimized. Microbial testing is important for monitoring product quality and safety and as a result, many sampling methods have been developed to evaluate the microbial quality of meat to provide microbiologically acceptable meat and meat products for the public. The purpose of this study was to evaluate the effectiveness of swabbing, rinsing, and grinding (followed by rinsing of the ground sample) as sampling methods for the recovery of indicator microorganisms on beef trimmings, and to determine which method is best suited to estimate the microbial numbers in beef trimmings. A total of fifteen samples of beef trimmings were collected at Texas Tech Gordon Davis Meat Laboratory using the N60 technique under federal inspection. Each sample was subjected to multiple sequential samplings: three times for each sampling method. A comparison was made between the first sampling and the total bacteria recovered by each method. The first and the total aerobic counts obtained by the rinse and the grinding methods resulted in aerobic bacteria counts that were not significantly different (P > 0.05). However, swabbing yielded counts that were significantly lower (P < 0.05) than both rinsing and grinding. In respect to total coliforms, rinsing was not significantly different (P < 0.05) from either swabbing or grinding, yet swabbing recovered the least number of bacteria from the samples. Escherichia coli biotype I was below the detectable limit regardless of the sampling technique used. Within each sampling method, the decline in aerobic bacteria counts due to multiple sequential sampling was calculated. Rinsing and grinding dropped significantly (P < 0.05) after the initial samplings, whereas swabbing did not (P > 0.05). Linear regression models were performed to observe the relationship among all possible pairs of sampling methods implemented in this study. Linear models showed strong relationships, with a coefficient of determination (r2) of 0.81 (swabbing vs grinding), 0.67 (swabbing vs rinsing), and 0.70 (rinsing vs grinding). Our findings suggest that although grinding resulted in the highest numerical recovery, the rinsing recovery was not significantly different. Therefore, any of these methods could be utilized to obtain a good representation of the number of bacteria in beef trimmings.