Osmotically dehydrated and air dried berry fruits are used as ingredients for the production of yoghurts, chocolates, cereal bars and mixes, ice creams and cakes and these fruits are often subjected to mild thermal treatments only, posing questions around their microbiological safety. As osmotic dehydration methods and parameters vary considerably within the industry and minimally processed high quality fruits are increasingly sought, the scope of this study was to determine which temperatures are required for the inactivation of relevant bacteria and viruses during osmotic dehydration of berries, using blueberries as a model berry in a thawed state to mimic common industrial practices. Additionally, we studied the inactivation of osmotic dehydration at 23 °C, sometimes referred to "cold infusion" followed by air drying at 100 °C to determine the microbiological safety achieved by this combined treatment. Four pathogens (Salmonella enterica, Escherichia coli O157:H7, Listeria monocytogenes and hepatitis A virus (HAV)) and five surrogates (Enterococcus faecium, Escherichia coli P1, Listeria innocua, murine Norovirus (MNV) and bacteriophage MS2) were inoculated on blueberries and reductions were measured after different treatment combinations. After osmotic dehydration of bacterial strains at 40 °C no survivors were detected on blueberries, with the exception of E. faecium. Inactivation of the viruses at 45 °C showed no survivors for MS2 and mean reductions of 1.5 and 3.4 log10 median tissue culture infectious dose (TCID50)/g for HAV and MNV, respectively. Similarly, in the sugar solution at 40 °C, no survivors were observed, with the exception of E. faecium and the three viruses. The combined process (osmotic dehydration at 23 °C followed by air-drying at 100 °C) achieved an >6 log reduction of all tested bacterial strains and MS2. For HAV and MNV, 2.6 and >3.4 log10 TCID50/g were measured. In summary, the present study shows that osmotic dehydration appears an efficient control measure for the control of L. monocytogenes, S. enterica and E. coli O157:H7 if carried out at 40 °C or at 23 °C and followed by air-drying at 100 °C. Based on the results generated with MNV, the combined treatment is also expected to reduce human Norovirus (NoV) but does not appear to be sufficient to fully control HAV. The results contribute to a better management of the microbial safety of osmotically dehydrated and dried berries and especially the results generated for the viruses emphasize that within a robust food safety management system, safety must be assured through the entire food supply chain and therefore must start at primary production with the implementation of Good Agricultural Practices (GAP).

中文翻译：

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沙门氏菌，产志贺毒素的大肠杆菌，单核细胞增生性李斯特菌，甲型肝炎病毒和蓝莓中的替代物的渗透脱水和空气干燥可使其失活。

渗透脱水和风干的浆果被用作生产酸奶，巧克力，谷物棒和混合物，冰淇淋和蛋糕的原料，这些水果通常仅经过温和的热处理，从而对微生物的安全性提出了质疑。随着行业内渗透脱水方法和参数的变化很大，并且越来越多地寻求加工程度最低的高质量水果，本研究的范围是确定蓝莓在渗透脱水过程中灭活相关细菌和病毒所需的温度。在融化状态下模仿普通工业惯例的标准浆果。此外，我们研究了在23°C时渗透失水的失活，有时也称为“冷输液” 然后在100°C下风干，以确定通过这种联合处理所获得的微生物安全性。在蓝莓和蓝莓上接种了四种病原体（肠炎沙门氏菌，大肠杆菌O157：H7，单核细胞增生李斯特菌和甲型肝炎病毒（HAV））和五种替代物（粪肠球菌，大肠杆菌P1，利斯特氏菌，鼠诺如病毒（MNV）和噬菌体MS2）。在不同的治疗组合后测量减少量。细菌菌株在40°C渗透压脱水后，除粪肠球菌外，在蓝莓上均未检测到任何幸存者。病毒在45°C下失活表明MS2没有存活，HAV和MNV分别平均降低了1.5和3.4 log10 log10中位数组织培养感染剂量（TCID50）/ g。同样，在40°C的糖溶液中，未观察到任何幸存者，除了粪肠球菌和三种病毒。组合的过程（在23°C下进行渗透性脱水，然后在100°C下进行风干）实现了所有测试细菌菌株和MS2的> 6 log减少。对于HAV和MNV，测得2.6和> 3.4 log10 TCID50 / g。总而言之，本研究表明，如果在40°C或23°C的温度下进行空气渗透脱水，则渗透脱水似乎是控制单核细胞增生李斯特菌，肠炎沙门氏菌和大肠杆菌O157：H7的有效控制措施。在100°C下干燥。基于MNV产生的结果，联合治疗也有望减少人诺如病毒（NoV），但似乎不足以完全控制HAV。