Validation Study of LuciPacTM A3 Surface for Hygiene Monitoring through Detection of ATP, ADP, and AMP from Stainless Steel Surfaces: AOAC Performance Tested MethodSM 051901.

BACKGROUND: The LuciPac A3 Surface Hygiene Monitoring System based on the detection of total adenylate, ATP+ADP+AMP (A3), has been developed by Kikkoman Biochemifa. OBJECTIVE: This A3 swabbing assay kit was validated for Performance Tested MethodsSM (PTM) certification. METHODS: The LuciPac A3 Surface Hygiene Monitoring System was evaluated for limit of detection (LOD) for each adenylate with pure analyte solutions, detection of food residues and microbial residues on stainless steel surfaces, interference by disinfectants, and selectivity of the method response. RESULTS: Pure analyte studies performed by the method developer and the independent laboratory showed good linearity (R2 > 0.9854) and repeatability precision (RSDr < 20% for ≥2.5 fmol/assay). The LOD values for each adenylate were around 10 relative light units or 2.5 fmol/assay. The repeatability precision in the method developer laboratory for the matrix study (raw chicken breast, sliced deli ham, orange juice, yogurt, and apple pie) and the microbial study (Cronobacter sakazakii, Lactobacillus acidophilus, and Saccharomyces cerevisiae) were 8-30% and 10-35%, respectively. The repeatability precision of independent laboratory testing was 13-27% for orange juice and 16-43% for ham. Interference by several disinfectants indicate that rinsing is recommended to be performed after the use of sanitizing agents and before testing with LuciPac A3 Surface. Selectivity testing revealed that no positive interference and no inhibition were caused by adenylate analogues. Instrument variation, lot-to-lot consistency, accelerated stability (30°C, 5 weeks) were confirmed, and the method was shown to be robust against shaking time. CONCLUSIONS: The LuciPac A3 Surface has been successfully validated. HIGHLIGHTS: This A3 swabbing assay kit was qualified for PTM certification No. 051901.

Evaluation of an improved bioluminescence assay for the detection of bacteria in soy milk.

Because soy milk is nutrient rich and nearly neutral in pH, it favors the growth of microbial contaminants. To ensure that soy milk meets food-safety standards, it must be pasteurized and have its sterility confirmed. ATP bioluminescence assay has become a widely accepted means of detecting food microorganisms. However, the high background bioluminescence intensity of soy milk has rendered it unsuitable for ATP analysis. Here, we tested the efficacy of an improved pre-treated bioluminescence assay on soy milk. By comparing background bioluminescence intensities obtained by the conventional and improved methods, we demonstrated that our method significantly reduces soy milk background bioluminescence. The dose-response curve of the assay was tested with serial dilutions of Bacillus sp. culture. An extremely strong log-linear relation between the bioluminescence intensity relative light units and colony formation units CFU/ml emerged for the tested strain. The detection limit of the assay was estimated as 5.2×10(3) CFU/ml from the dose-response curve and an imposed signal limit was three times the background level. The results showed that contaminated samples could be easily detected within 24 h using our improved bioluminescence assay.