Department of Animal and Food Sciences, University of Delaware, Newark, DE 19716-2150, USA.
Int J Food Microbiol. 2013 Jan 1;160(3):337-43. doi: 10.1016/j.ijfoodmicro.2012.11.008. Epub 2012 Nov 20.
The objectives of this study were to investigate the survival of Escherichia coli O157:H7 and Salmonella spp. in frozen strawberry puree and to assess the application of high pressure processing (HPP) to decontaminate strawberry puree from both pathogens. Fresh strawberry puree was inoculated with high (6 log CFU/g) and low (3 log CFU/g) levels of E. coli O157:H7 or Salmonella spp. and stored at -18°C for 12 weeks. Both pathogens were able to persist for at least 4weeks and samples with high inoculums were still positive for both pathogens after 12 weeks. Pressure treatment of 450 MPa for 2 min at 21°C was able to eliminate both pathogens in strawberry puree. Frozen storage at -18°C after pressure treatment substantially enhanced the inactivation of both pathogens and 4-8 days of frozen storage was able to reduce the pressure level needed for elimination of both pathogens to 250-300 MPa. Natural yeasts and molds in strawberry puree were effectively reduced by pressure of 300 MPa for 2 min at 21°C. No adverse impacts on physical properties such as color, soluble solids content, pH and viscosity of strawberry puree was found for pressure-treated samples. Therefore, the treatment of 300 MPa for 2 min at 21°C followed by 4 days frozen storage at -18°C was recommended for the minimal processing of strawberry puree with great retention of fresh-like sensory properties. HPP could be a promising alternative to traditional thermal processing for berry purees.
本研究的目的是研究大肠杆菌 O157:H7 和沙门氏菌在冷冻草莓泥中的存活情况，并评估高压处理（HPP）对去除草莓泥中这两种病原体的应用。将新鲜的草莓泥接种高（6 log CFU/g）和低（3 log CFU/g）水平的大肠杆菌 O157:H7 或沙门氏菌，并在-18°C下储存 12 周。这两种病原体都能至少存活 4 周，高接种量的样品在 12 周后仍对这两种病原体呈阳性。21°C 下 450 MPa 处理 2 分钟能够消除草莓泥中的这两种病原体。压力处理后在-18°C 下冷冻储存大大增强了这两种病原体的失活作用，4-8 天的冷冻储存能够将消除这两种病原体所需的压力水平降低到 250-300 MPa。21°C 下 300 MPa 处理 2 分钟能够有效减少草莓泥中的天然酵母和霉菌。对经过压力处理的样品的物理性质（如颜色、可溶性固形物含量、pH 值和粘度）没有发现任何不良影响。因此，建议采用 21°C 下 300 MPa 处理 2 分钟，然后在-18°C 下冷冻储存 4 天，作为最小化处理具有新鲜感官特性的草莓泥的方法。HPP 可能是浆果泥传统热加工的有前途的替代方法。
