Development of a Novel Hygiene Monitoring System Based on the Detection of Total Adenylate (ATP+ADP+AMP)

ATP is the universal energy molecule found in animals, plants, and microorganisms. ATP rapid hygiene monitoring tests have been employed in the food industry to ensure that adequate cleanliness is being maintained. However, because ATP is hydrolyzed to ADP and AMP by metabolic processes, by heat treatment, or under acidic or alkaline conditions, total adenylate (ATP+ADP+AMP [A3]) could be a more reliable sanitation indicator of food residues that may cause biofilm formation and allergen contamination. Therefore, a novel hygiene monitoring system to measure A3 was developed based on the luciferin-luciferase assay with the combination of two enzymes, pyruvate kinase and pyruvate phosphate dikinase, that can convert ADP into ATP and recycle AMP into ATP, respectively. The newly developed A3 assay system afforded stable bioluminescence signals and equivalent linear calibration curves between relative light units (RLU) and the amounts of ATP, ADP, and AMP, respectively. To verify the significance of the A3 method, the ratios of ATP, ADP, and AMP in various food samples were determined; large amounts of ADP and AMP were found in a variety of foods, such as meat, seafood, dairy, nuts, fruits, vegetables, and fermented foods. Sanitation monitoring of stainless steel exposed to raw meat was also examined, and the A3 method achieved a 200-RLU level, the typical benchmark value, after complete washing with detergent and rinsing. In contrast, a conventional ATP method showed less than 200 RLU after only a light cold and hot water rinse. In conclusion, the A3 assay appeared to be suitable for detection of adenylates from food residues that are not detected by the conventional ATP assay.