Evaluation of Methods for Estimation of Viable Bacterial Count of Raw Meat

Abstract

An improved method was developed for the estimation of viable bacterial counts for raw meat stored at low temperature, and was used to analyze the influence of various factors affecting the viable bacterial count. The viable bacterial counts of 40 samples each of commercial cut beef, pork, and chicken meat stored refrigerated or frozen in the raw state were estimated comparatively by using three methods of sample inoculation, i. e., the surface plate method and the pour plate method poured at 50 and 60°C with standard plate count agar, at six incubation temperatures (7, 25, 30, 32, 35, and 37°C).1) Among the three methods of inoculation, the viable bacterial count was the highest in the surface plate method, regardless of temperature of culture. As regards the temperature of culture, the count was the highest in the culture at 25°C, regardless of the method of inoculation used. Therefore, the count was the highest when the surface plate method was performed at 25°C.2) The viable bacterial count was significantly higher when estimated by the surface plate method at 25°C than when estimated by the method prescribed in the Official Guideline of Sanitary Tests of Food with culture at 35°C.3) There was a significant correlation between the viable bacterial count estimated by the surface plate method at 25°C and that at any other temperature.4) The mode of storage (refrigeration or freezing) was the most influential factor upon the viable bacterial count. The next most important factor was the kind of meat (beef, pork, or chicken), followed by the temperature of culture, and the method of inoculation in decreasing order of influence upon the count.