Efficacy of ATP Monitoring for Measuring Organic Matter on Postharvest Food Contact Surfaces

The Food Safety Modernization Act, specifically the Produce Safety Rule, requires growers to clean and sanitize food contact surfaces to protect against produce contamination. An ATP monitoring device is a potential sanitation tool to monitor the efficacy of an on-farm cleaning and sanitation program that could help growers meet regulatory expectations mandated by the Produce Safety Rule. This ATP monitoring device uses bioluminescence to detect all ATP (found in bacteria and produce matter cells) from a swabbed surface. Because little work has been done to test the efficacy of these tools under postharvest conditions, the present study evaluated ATP measurement for postharvest food contact surface cleanliness evaluation. Concentrations of leafy greens (spinach, romaine, and red cabbage, with or without Listeria innocua) were used as organic matter applied to stainless steel, high-density polyethylene plastic, and bamboo wood coupons to represent postharvest food contact surfaces. The ATP levels on the coupons were then measured by using swabs and an ATP monitoring device. Results showed that the concentration of L. innocua and leafy greens on a food contact surface had a highly significant effect on the ATP monitoring device reading (P < 0.0001). The ATP monitoring device had a lower limit of detection for L. innocua at 4.5 log CFU per coupon. The type of leafy green on a food contact surface did not affect the ATP reading (P = 0.88). Leafy greens with added L. innocua had a higher ATP reading when compared with saline and L. innocua, demonstrating the presence of leafy green matter contributes to ATP reading when combined with L. innocua. The different food contact surfaces had different ATP response readings (P = 0.03), resulting in no detectable levels of bacteria and/or leafy green material from bamboo wood surfaces (P = 0.16). On the basis of our results, the ATP measurement is an appropriate tool to measure produce or bacterial contamination on stainless steel or high-density polyethylene plastic surfaces; however, it is not recommended for wood surfaces.