Department of Food Science and Technology, University of Córdoba, Campus de Rabanales, C-1, 14014 Córdoba, Spain; International Campus of Excellence in the AgriFood Sector (CeIA3), Spain.
Norwegian Veterinary Institute, Section for Bacteriology-Food and GMO, P.O. Box 750 Sentrum, 0106 Oslo, Norway.
Int J Food Microbiol. 2014 Aug 1;184:92-7. doi: 10.1016/j.ijfoodmicro.2014.03.026. Epub 2014 Mar 29.
The present work aimed at studying the cross contamination of apples by Salmonella during the processing of commercial fresh apples and its survival capacity on apple at room temperature. For the first study, the typical process of fresh apples was simulated at laboratory scale in which an apple that was artificially contaminated by Salmonella at different concentration levels (8, 6 and 5 log cfu/apple) was introduced in one batch and processed including a simulated transport/washing step and drying step using sponges to simulate the porous material used in the industry. Results indicated that at 8 log cfu/apple, 50% fresh apples were contaminated after processing, with all analysed environmental samples being positive for the pathogen, consisting of washing water and sponges. However, at lower inoculum levels (5-6 log cfu/apple) no cross contamination was detected in apples, and only environmental samples showed contamination by Salmonella after processing including both water and sponges. Experiments on the survival of Salmonella on apple showed that the pathogen was capable to survive for 12 days, only showing a significant drop at the end of the experiment. Finally, two-class attribute sampling plans were assessed as tool to detect Salmonella in different contamination scenarios in fresh apple. This analysis indicated that with the highest inoculum level, a total of 16 apples would be needed to reach 95% of detecting Salmonella (i.e. lot rejection). In turn, when low levels were assessed (5-6 log cfu/apple), a large number of apples (n=1021) would have to be sampled to obtain the same confidence level (95%). If the environment is sampled (i.e. water and sponges), a lower number of samples would be needed to detect the pathogen. However, the feasibility of environmental sampling has not been assessed from a practical point of view. Overall, the results in this study evidenced that cross contamination by Salmonella might occur during processing of fresh apples and subsequently, the pathogen might survive for a noticeable period of time.
本研究旨在研究商业新鲜苹果在加工过程中沙门氏菌的交叉污染及其在室温下苹果上的存活能力。在第一项研究中，以实验室规模模拟了新鲜苹果的典型加工过程，将人工污染不同浓度水平（8、6 和 5 log cfu/苹果）的沙门氏菌的苹果引入一批，并进行加工，包括模拟运输/清洗步骤和使用海绵干燥步骤，以模拟工业中使用的多孔材料。结果表明，在 8 log cfu/苹果的水平下，加工后有 50%的新鲜苹果受到污染，所有分析的环境样本均为该病原体阳性，包括洗涤水和海绵。然而，在较低的接种水平（5-6 log cfu/苹果）下，苹果中未检测到交叉污染，仅在加工后包括水和海绵在内的环境样本中检测到沙门氏菌污染。沙门氏菌在苹果上存活的实验表明，该病原体能够存活 12 天，仅在实验结束时才显示出显著下降。最后，评估了二类属性抽样计划作为在新鲜苹果不同污染情况下检测沙门氏菌的工具。该分析表明，在最高接种水平下，需要总共 16 个苹果才能达到 95%的沙门氏菌检出率（即批拒收）。相反，在评估低水平（5-6 log cfu/苹果）时，需要对大量苹果（n=1021）进行采样，才能获得相同的置信水平（95%）。如果对环境进行采样（即水和海绵），则需要较少的样本才能检测到病原体。然而，尚未从实际角度评估环境采样的可行性。总体而言，本研究结果表明，沙门氏菌可能在新鲜苹果的加工过程中发生交叉污染，随后病原体可能存活相当长的一段时间。
