Hamilton Alexis, Ruiz-Llacsahuanga Blanca, Mendoza Manoella, Mattheis James, Hanrahan Ines, Critzer Faith J
School of Food Science, Irrigated Agriculture Research and Extension Center, Washington State University, Prosser, Washington 99350.
Washington Tree Fruit Research Commission, 1719 Springwater Avenue, Wenatchee, Washington 98801.
J Food Prot. 2022 Jan 1;85(1):133-141. doi: 10.4315/JFP-21-232.
Recent apple-related recall and outbreak events have exposed a need for better food safety controls along the supply chain. Following harvest, apples can be stored under a controlled atmosphere for up to 1 year after harvest before packing and distribution, making the crop susceptible to many opportunities for contamination that increase the quantity of postharvest losses. Botrytis cinerea and Penicillium expansum cause significant rot-associated losses to the apple industry. These fungi can colonize and destroy apple tissue as storage duration increases, which may also impact the growth of saprophytic foodborne pathogens like Listeria monocytogenes. Thus, the objective of this study was to observe population changes of Listeria innocua as a surrogate for L. monocytogenes on apples inoculated with B. cinerea or P. expansum under long-term controlled atmosphere cold storage conditions to identify the effect of postharvest mold growth on growth patterns of a microorganism relevant to food safety. 'Gala' and 'WA 38' apples (n = 1,080) were harvested, treated with pyrimethanil, and inoculated with L. innocua only or with L. innocua and one of the mold species on wounded and unwounded portions of the apple equator. Apples were treated with 1-methylcyclopropene and stored at a controlled atmosphere (2 kPa O2, 1 kPa CO2, 1°C) for 1 week and 1, 3, 6, 9, and 11 months before enumeration. After 3 months, L. innocua consistently fell below the limit of detection (2.35 Log CFU/g), and samples were enriched following a modified Bacteriological Analytical Manual method with PCR confirmation. Listeria persistence was dependent on the storage duration and type of fungal contamination (P ≤ 0.05). Surface wounding may impact these trends, depending on the apple variety. Prevalence of L. innocua was greater in Gala apples. Future studies should more closely examine the interactions on the fruit surface that occur during the seemingly critical time frame of 3 to 6 months in storage.
近期与苹果相关的召回和疫情事件暴露了供应链中加强食品安全控制的必要性。收获后，苹果在包装和分销前可在可控气氛下储存长达1年，这使得该作物容易受到许多污染机会的影响，从而增加了采后损失的数量。灰葡萄孢和扩展青霉给苹果产业造成了与腐烂相关的重大损失。随着储存时间的增加，这些真菌会定殖并破坏苹果组织，这也可能影响诸如单核细胞增生李斯特菌等腐生性食源性病原体的生长。因此，本研究的目的是观察无害李斯特菌作为单核细胞增生李斯特菌的替代菌在长期可控气氛冷藏条件下接种了灰葡萄孢或扩展青霉的苹果上的种群变化，以确定采后霉菌生长对与食品安全相关的微生物生长模式的影响。收获了“嘎啦”和“华红”苹果（n = 1080），用嘧霉胺处理，并仅接种无害李斯特菌，或在苹果赤道的受伤和未受伤部位接种无害李斯特菌和其中一种霉菌。苹果用1-甲基环丙烯处理，在可控气氛（2 kPa氧气、1 kPa二氧化碳、1°C）下储存1周、1、3、6、9和11个月后进行计数。3个月后，无害李斯特菌始终低于检测限（2.35 Log CFU/g），样品按照改良的《细菌学分析手册》方法进行富集并经PCR确认。李斯特菌的持续存在取决于储存时间和真菌污染类型（P≤0.05）。表面伤口可能会影响这些趋势，这取决于苹果品种。无害李斯特菌在嘎啦苹果中的流行率更高。未来的研究应更密切地研究在储存3至6个月这一看似关键的时间段内果实表面发生的相互作用。
