Evaluation of Diluents Used for Total Counts1

Abstract

A comparison was made between Butterfield's buffered phosphate solution. 0.1% peptone in distilled water. 0.5% peptone in distilled water, 0.85% NaCl in distilled water, and pure distilled water as diluents for total bacterial counts of 28 different food samples. Plates were incubated at 35 and 22 C for 2 and 5 days, respectively. Butterfield's diluent afforded the highest overall mean count for most samples regardless of the incubation temperature. Highest counts occurred with all diluents at 22 C. Although Butterfield's diluent. 0.1% peptone, and 0.5% peptone appeared to yield higher counts for most samples than did distilled water or 0.85% NaCl, statistically the mean counts obtained for the live diluents used were not significantly different from each other. It appears that no single diluent is suited for every possible sample type.