Rapid Quantitative Enumeration of Aerobic Count Bacteria in Foods

Introduction: Aerobic count bacteria are ubiquitously present in a variety of food matrices and serve as indicators for food spoilage. These microorganisms can grow in a wide range of temperatures and pH values thus having the potential for substantial economic losses to the food industry. These organisms have become important indicators for monitoring food quality but the 48 hour incubation required by traditional enumeration methods poses a burden on food producers. A novel dehydrated film medium was developed to address the need for rapid (24 hour) detection of aerobic bacteria. The detection technology was optimized to overcome the inherent limitations associated with over expression of extracellular enzymes by certain spore formers that results in liquefaction of the dehydrated film media.

Purpose: This study was performed to comparatively enumerate aerobic count bacteria using a new dehydrated film medium and reference methodology as described in FDA/BAM and ISO 4833.

Methods: The method comparison was conducted using a variety of naturally contaminated food matrices (n > 75) with the new dehydrated film test method and a reference method (FDA/BAM and ISO4833). Each food sample was serially diluted in Butterfields buffer. One milliliter (ml) each of the sample or its dilution was used for the candidate and the reference method (Standard methods agar; pour plate method).

Results: Results were statistically comparable between the new dehydrated film method at 24 hrs to Standard Methods Agar at 48 hours (at 32°C or 35°C) or 72 hours (at 30°C) with no significant differences as indicated by the P values (> 0.05) and regression analysis.

Significance: Rapid quantitative detection of aerobic count bacteria using the new dehydrated film method was evaluated using a large number (n > 75) of naturally contaminated foods. The new method was found to provide actionable results in a shorter period of time, with significantly improved interpretation, without sacrificing performance which is critical for food processors.