Abstract Antimicrobial sanitizers applied through a manifold spray-bar brush bed system is a main intervention strategy to prevent cross-contamination of foodborne pathogens on fresh apples. To date, information about antimicrobial efficacy of sanitizers including peroxyacetic acid (PAA) intervention is mainly based on laboratory submerging testing which cannot be directly applied into spray-bar system in apple processing facility due to differences in processing parameters. Previously, we examined anti-Listeria efficacies of PAA in laboratory testing. The studies herein further verified the effectiveness of the selected PAA treatments in a pilot apple spray processing line against Listeria monocytogenes surrogate strains, Enterococcus faecium NRRL B-2354 and Listeria innocua, on apples of the selected varieties. The quality attributes of apples after the selected treatments were further evaluated. A 2-min, 80 ppm PAA treatment at 43 °C and 46 °C resulted in 2.4 and 2.4–2.7 Log10 CFU/apple reduction of E. faecium on different apple varieties, respectively, which had similar reductions compared to L. monocytogenes (2.3–2.5 and 2.5–2.8 Log10 CFU/apple reduction), indicating that E. faecium NRRL B-2354 is a suitable surrogate of L. monocytogenes for evaluating PAA efficacy at test temperatures (22–46 °C). Using this pilot spray-bar system, we further showed that a 30-sec spray wash of 80 ppm PAA at 22 °C and 44–46 °C resulted in 0.8–1.1 and 1.5–1.6 Log10 CFU/apple reduction of E. faecium on apple of the selected varieties, respectively, which were comparable to those of L. innocua. In addition, PAA applied at 44–46 °C did not affect the firmness, total soluble solids content and titratable acidity of apple fruits of tested varieties compared to its application at ambient temperature over 3-week of commercial storage. This study showed that E. faecium NRRL B-2354 is a suitable surrogate strain of L. monocytogenes during the pilot fresh apple processing and provides valuable practical data of PAA spray-bar intervention to the apple industry, facilitating compliance with the Preventive Controls for Human Food Rule.

中文翻译：

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在试验喷雾棒过氧乙酸干预期间验证屎肠球菌 NRRL B-2354 作为新鲜苹果上单核细胞增生李斯特菌的替代品

摘要 通过歧管喷杆刷床系统应用抗菌消毒剂是防止新鲜苹果上食源性病原体交叉污染的主要干预策略。迄今为止，关于包括过氧乙酸 (PAA) 干预在内的消毒剂的抗菌功效的信息主要基于实验室浸没测试，由于加工参数的差异，不能直接应用于苹果加工设施的喷杆系统。之前，我们在实验室测试中检查了 PAA 的抗李斯特菌功效。本文的研究进一步验证了选定的 PAA 处理在试验性苹果喷雾加工生产线中对选定品种的苹果对单核细胞增生李斯特菌替代菌株、屎肠球菌 NRRL B-2354 和无害李斯特菌的有效性。对选定处理后苹果的品质属性进行了进一步评估。在 43 °C 和 46 °C 下进行 2 分钟、80 ppm 的 PAA 处理导致不同苹果品种上的粪肠球菌分别减少了 2.4 和 2.4–2.7 Log10 CFU/苹果，与单核细胞增生李斯特菌相比具有相似的减少量（ 2.3–2.5 和 2.5–2.8 Log10 CFU/苹果减少），表明屎肠球菌 NRRL B-2354 是单核细胞增生李斯特菌的合适替代品，可用于在测试温度（22–46 °C）下评估 PAA 功效。使用该试验喷杆系统，我们进一步表明，在 22 °C 和 44–46 °C 下用 80 ppm PAA 喷洗 30 秒可减少 0.8–1.1 和 1.5–1.6 Log10 CFU/苹果 粪肠球菌在所选品种的苹果上，分别与 L. innocua 相当。此外，PAA 在 44–46 °C 下应用不会影响硬度，测试品种的苹果果实的总可溶性固形物含量和可滴定酸度与其在环境温度下超过 3 周的商业储存应用相比。本研究表明，粪肠球菌 NRRL B-2354 是试验性新鲜苹果加工过程中单核细胞增生李斯特氏菌的合适替代菌株，并为苹果行业提供了宝贵的 PAA 喷杆干预实用数据，有助于遵守人类预防控制措施食物规则。