Department of Food Science and Technology, Kongju National University, Yesan, Chungnam, 32439, Republic of Korea.
Department of Food and Animal Biotechnology, Department of Agricultural Biotechnology, Center for Food and Bioconvergence and Research Institute for Agriculture and Life Sciences, Seoul National University, Seoul, 151-921, Republic of Korea.
Food Microbiol. 2023 Sep;114:104302. doi: 10.1016/j.fm.2023.104302. Epub 2023 Apr 29.
The objectives of this study were to evaluate the survival of high hydrostatic pressure (HHP)-treated Salmonella Typhimurium, Escherichia coli O157:H7, and Listeria monocytogenes in apple puree, as well as to determine the levels of HHP-induced cell injury according to the pressure level, holding time, and pH of apple puree. Apple puree was inoculated with three foodborne pathogens and treated at pressures of 300-600 MPa for up to 7 min at 22 °C using HHP equipment. Increasing the pressure level and lowering the pH of apple puree led to larger microbial reductions, and E. coli O157:H7 showed higher resistance compared to S. Typhimurium and L. monocytogenes. Besides, approximately 5-log injured cells of E. coli O157:H7 were induced in apple puree at pH 3.5 and 3.8. HHP treatment at 500 MPa for 2 min effectively achieved complete inactivation of the three pathogens in apple puree at pH 3.5. For apple puree at pH 3.8, more than 2 min treatment of HHP at 600 MPa is seemingly needed to achieve complete inactivation of the three pathogens. Transmission electron microscopy analysis was conducted to identify ultrastructural changes in the injured or dead cells after HHP treatment. Plasmolysis and uneven cavities in the cytoplasm were observed in injured cells, and additional deformations, such as distorted and rough cell envelopes, and cell disruption occurred in dead cells. No changes in solid soluble content (SSC) and color of apple puree were observed after HHP treatment, and no differences were detected between control and HHP-treated samples during 10 d of storage at 5 °C. The results of this study could be useful in determining the acidity of apple purees or the treatment time at specific acidity levels when applying the HHP processing.
本研究的目的是评估高压处理（HHP）对苹果泥中肠炎沙门氏菌、大肠杆菌 O157:H7 和李斯特菌的生存能力，以及根据苹果泥的压力水平、保持时间和 pH 值确定 HHP 诱导的细胞损伤水平。将三种食源性致病菌接种到苹果泥中，然后使用 HHP 设备在 22°C 下于 300-600 MPa 的压力下处理长达 7 分钟。提高压力水平和降低苹果泥的 pH 值会导致更大的微生物减少，并且大肠杆菌 O157:H7 比肠炎沙门氏菌和李斯特菌具有更高的抗性。此外，在 pH 值为 3.5 和 3.8 的苹果泥中，大约有 5 个对数的大肠杆菌 O157:H7 受伤细胞被诱导。在 pH 值为 3.5 的苹果泥中，HHP 处理 500 MPa 2 分钟即可有效实现三种病原体的完全失活。对于 pH 值为 3.8 的苹果泥，似乎需要 600 MPa 的 HHP 处理超过 2 分钟才能实现三种病原体的完全失活。透射电子显微镜分析用于鉴定 HHP 处理后受伤或死亡细胞的超微结构变化。在受伤细胞中观察到质膜质溶胀和细胞质不均匀空洞，在死亡细胞中观察到额外的变形，如扭曲和粗糙的细胞膜和细胞破裂。HHP 处理后苹果泥的固溶物含量（SSC）和颜色没有变化，在 5°C 下储存 10 天期间，对照和 HHP 处理样品之间没有差异。本研究的结果可用于确定苹果泥的酸度或在特定酸度水平下应用 HHP 处理时的处理时间。
