Comparative Performance of Easy Plate AC-R for Rapid Aerobic Bacteria Count in Multiple Food Types

Introduction:

The aerobic plate count is crucial in food microbiological testing, but traditional methods such as Plate Count Agar (PCA) take 48 hours for enumeration. The newly developed ready-to-use (RTU) media for aerobic bacteria count, Easy Plate AC-R (RTU-A) byKikkoman Biochemifa Company, are convenient and environmentally friendly, and allow for rapid enumeration in just 24 hours.

Purpose:

The enumeration performance of RTU-A, PCA, and three other RTU media (RTU-X, RTU-Y, RTU-Z) was compared using various commercially available food samples. Method: Sixty-four food matrices, including meats, seafoods, vegetables, fruits, dairy products, and prepared foods such as RTE foods and dried foods, were used for evaluation. Each medium was inoculated with 1 mL of food dilution and incubated at 35±1 °C. Colony counts were performed visually at 24±1 hours for RTU media and at 48±2 hours for PCA. Counts for RTU-A were performed not only visually but also using Colony Counting System (CCS).

Result:

The correlation coefficients between RTU-A and PCA, as well as RTU-X, RTU-Y, and RTU-Z, were 0.986, 0.990, 0.993, and 0.996, respectively. RTU-A demonstrated equivalent enumeration performance to PCA at 48 hours incubation, with comparable results achieved in just 24 hours. in addition, the correlation coefficient between visual colony counts and those obtained by CCS for RTU-A was 0.979. CCS tended to detect higher numbers of colonies compared to visual counting, confirming its ability to accurately count small and pale colonies.

Significance:

The newly developed RTU-A has demonstrated the ability to perform aerobic bacteria count in significantly less time than conventional PCA methods. When combined with CCS, it is expected to further reduce operator workload, standardize processes and improve traceability.