Summary: The significance in food microbiology of the observation of Stapert, Sokolski & Northam (1962), that some bacteria occurring in water have such low heat resistances that they would be affected by the warm agar used for pouring plates, was tested. Forty‐two samples of 6 different foods stored for 7 days at 3° to enrich their psychrotrophic microflora, were examined using the same medium, but in thin poured plates and on spread plates, respectively, incubated at 14°. The logarithmic average count of the foods was c. 10 8 /g and included about 60% Gram‐negative rods and 30% cocci. In 90% of the samples no differences were observed between the results from the two methods of counting. The slightly higher spread plate counts in the remaining instances could be accounted for by the increased disruption of bacterial agglomerations always observed in this procedure. Hence there is no reason to query the results of poured plate counts in general. Where it is yet probably safer to use spread plates, rigorous asepsis in pouring and storing should be observed to prevent the development of colonies of contaminants too small to be detected when the plates are inoculated, but leading to erroneous counts after incubation.
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Mossel et al. (1964) studied this question.