Enumeration of micro-organisms in food: a comparative study of five methods.

Five methods for the enumeration of micro-organisms in food (pour plate, surface spread plate, surface drop, agar droplet, and microdilution) were used in parallel to examine 100 samples selected from a wide range of food products. Statistical analyses of the results showed that the regression and correlation coefficients between the methods were highly significant; the lowest correlation coefficient derived for any pair of methods was 0.979. A variation in count between the methods of less than 0.5 log10 cycles was given by 98% of the samples. Analysis of the operation times and material requirements of each method showed that substantial savings in cost, time, space and support labour were achieved with the microdilution and agar droplet techniques as compared with the conventional pour plate and spread plate methods.