Departamento de Salud Pública, CUCBA, Universidad de Guadalajara, Zapopan, Jalisco 45110, Mexico.
Departamentos de Farmacobiología y Matemáticas, CUCEI, Universidad de Guadalajara, Guadalajara, Jalisco 44430, Mexico.
Int J Food Microbiol. 2022 May 16;369:109614. doi: 10.1016/j.ijfoodmicro.2022.109614. Epub 2022 Mar 7.
Avocados are popular fruits; however, contamination of whole fresh avocados and avocado products with foodborne pathogens has raised concern about their safety. Recalls and import alerts of avocado products due to contamination with Listeria monocytogenes cause important economic losses. The behavior of Salmonella, L. monocytogenes, and background microbiota on whole fresh avocados at 5 and 25 °C as affected by temperature and time of storage was investigated. Whole fresh avocados were inoculated by immersion in suspensions containing six rifampicin-resistant strains of Salmonella or L. monocytogenes, and stored at 5 °C for 48 d, or at 25 °C for 11 d. At selected sampling times, avocados were removed from storage and pathogens enumerated. The log counts of both pathogens at each temperature were fitted to the Weibull distribution nonlinear model to estimate kinetic parameters including the time for the first 1-log reduction (δ), the shape of the curve (ρ), and the time for two (2-D) and three (3-D) log reductions. Salmonella and L. monocytogenes initial populations (approx. 7 log CFU/avocado) decreased during storage at 5 and 25 °C; L. monocytogenes mean counts were higher than those observed for Salmonella (P < 0.05). L. monocytogenes showed a lower rate of decline at 5 °C when compared to Salmonella. In general, the ability of both pathogens to survive on the surface of avocados stored at room temperature was similar. Salmonella and L. monocytogenes counts decline over time on the epicarp of whole avocados; however, if the initial number of cells is large enough, the pathogens could be present for large periods of time. Simultaneously, psychrotrophic microorganisms (PM), aerobic plate count (APC), coliforms (C) and yeasts/molds (Y/M) were enumerated from non-inoculated avocados stored at 5 and 25 °C. Initial mean counts for PM, APC, C and Y/M ranged from 6.1 to 6.6 log CFU/avocado and showed no change (P > 0.05) during storage at both temperatures. Good agricultural and handling practices from farm to fork are crucial to prevent or minimize contamination of whole avocados; otherwise, if large numbers of pathogens contaminate the fruit, they could survive and be transferred to the pulp, or to other ready to eat foods, representing a risk for consumers.
鳄梨是一种受欢迎的水果；然而，由于食源性病原体的污染，整个新鲜鳄梨和鳄梨产品的安全性引起了人们的关注。由于单核细胞增生李斯特菌污染，鳄梨产品的召回和进口警报导致了重要的经济损失。本研究调查了温度和储存时间对 5 和 25°C 下整个新鲜鳄梨中沙门氏菌、单核细胞增生李斯特菌和背景微生物群的影响。将整个新鲜鳄梨浸入含有 6 株利福平抗性沙门氏菌或单核细胞增生李斯特菌的悬浮液中进行接种，并在 5°C 下储存 48 天，或在 25°C 下储存 11 天。在选定的采样时间，从储存中取出鳄梨并对病原体进行计数。在每个温度下，两种病原体的对数计数都拟合到威布尔分布非线性模型中，以估计包括首次 1 对数减少（δ）、曲线形状（ρ）以及 2-D 和 3-D 对数减少所需的时间在内的动力学参数。沙门氏菌和单核细胞增生李斯特菌的初始种群（约 7logCFU/鳄梨）在 5 和 25°C 下储存期间减少；单核细胞增生李斯特菌的平均计数高于沙门氏菌（P<0.05）。与沙门氏菌相比，单核细胞增生李斯特菌在 5°C 下的下降速度较慢。一般来说，两种病原体在室温下储存于鳄梨表面的存活能力相似。沙门氏菌和单核细胞增生李斯特菌在整个鳄梨果皮上的数量随时间减少；然而，如果初始细胞数量足够大，病原体可能会存在很长时间。同时，从 5 和 25°C 储存的未接种鳄梨中计数出嗜冷微生物（PM）、需氧平板计数（APC）、大肠菌群（C）和酵母菌/霉菌（Y/M）。PM、APC、C 和 Y/M 的初始平均计数范围为 6.1 至 6.6logCFU/鳄梨，在两种温度下储存期间均未发生变化（P>0.05）。从农场到餐桌的良好农业和处理实践对于防止或最大限度减少整个鳄梨的污染至关重要；否则，如果大量病原体污染了水果，它们可能会存活下来并转移到果肉中，或转移到其他即食食品中，这对消费者构成了风险。
