Comparison of 3 M^TM Petrifilm^TM Aerobic Count Plates with Pour Plates for Determination of Aerobic Plate Counts in Fermented Chile Mash

Fermented chile pepper mash is a major food product in New Mexico. There are few reports on the fermentation process or on methods to monitor it. In the current study we examined a pour plate procedure with an overlay using plate count agar and 3 M™ Petrifilm™ Aerobic Count (AC) plates for determination of total aerobic bacterial counts during the fermentation of chile mash. Fifty chile mash samples were obtained directly from commercial fermentation vats and examined within 2 h of collection. Serial dilutions of the chile mash were prepared in Butterfield's Phosphate Buffer. 1 mL portions of the diluted samples were aliquoted in duplicate onto the AC plates and into empty Petri dishes. Plate count agar was poured and once the plates had solidified, they were overlaid with about 10 mL of PCA to minimize spreaders. Plates were incubated at 30 °C for 48 h and enumerated. Paired difference tests were conducted on log transformed data to compare the results of the two plating procedures. For commercial chile mash samples, we did not show any significant differences between the AC plate counts and the pour plate counts (α = 0.05). 3 M™ Petrifilm™ AC plates are a good alternative to pour plates for the determination of the total aerobic counts in fermented chile mashes.