Efficacy of Peracetic Acid–based Sprays against Microbial Loads on Conveyors in a Walnut Hulling Facility

Association of foodborne pathogens with tree nuts has led to interest in microbial mitigation strategies that can be applied during postharvest handling and processing. The efficacy of commercial peracetic acid (PAA)-based sanitizer spray applications was evaluated for efficacy in reducing aerobic plate counts (APC) and Escherichia coli/ coliform counts (ECC) on conveyor belts in a commercial walnut huller. Water alone was compared to one of four PAA-based sanitizers at concentrations of 100 or 200 ppm PAA. APC and ECC were significantly (P < 0.05) lower on conveyor belts sprayed with 200 ppm PAA than on those sprayed with water. Significantly (P < 0.05) lower APC and ECC were observed on conveyor belts sprayed with one PAA formulation at 100 ppm (5.00 and 4.14 log CFU/100 cm2, respectively) than on those sprayed with water (6.40 and 6.10 log CFU/100 cm2, respectively). The efficacy of this sanitizer was not significantly different (P > 0.05) at 25, 50, 80, or 100 ppm (APC: 4.32 to 4.51 log CFU/100 cm2; ECC: 2.79 to 2.87 log CFU/100 cm2). PAA sprays reduce microbial levels on conveyer belt surfaces in walnut hulling facilities, which may reduce the potential for cross-contamination.