Rapid Hygiene Assay Sensitive to Cumulative Adenylate Homologues Exhibits Equal or Higher Frequencies of Soil Contamination Detection than Assay Limited to ATP Detection

Based upon regulatory and food industry-driven food safety standards, there is a need for rapid, accurate methods for assessing sanitary conditions. A commonly used assay is based on the assessment of the biochemical molecule adenosine triphosphate (ATP). A more recent assay, the total adenylate homologue-based (AXP) assay, targets the cumulative presence of ATP and its dephosphorylated homologues, adenosine diphosphate and adenosine monophosphate. Yet there is little information that compares the practical performance of these two assays. This work examined these two assay types with a comparative study in a grade A dairy foods processing plant and a licensed and inspected meat processing facility. A total of 1,920 concomitant analyses were conducted with main variables of assay type, processing facility type, and hygiene zone category. Statistical process control methodology was used to calculate 95% confidence control limits; data beyond those limits were considered contamination events. Results demonstrated that overall, the AXP assay detected contamination events approximately two times more often than the assay based on ATP only. This increase in the rate of contamination event detection was especially prevalent in the meat processing facility, where across all hygienic zones, there were 38 versus 85 contaminations events detected for the ATP and AXP assays, respectively. Across hygiene zones, the AXP data displayed either an equal or an increased incidence of soil detection compared with data from the ATP assay. This study provides applied evidence that assays solely dependent on ATP concentrations are less able to detect soil contaminants under conditions that favor ATP dephosphorylation reactions.