University of Alberta, Department of Agricultural, Food and Nutritional Science. 4-10 Agriculture/Forestry Centre, Edmonton, Alberta T6G 2P5, Canada.
University of Alberta, Department of Agricultural, Food and Nutritional Science. 4-10 Agriculture/Forestry Centre, Edmonton, Alberta T6G 2P5, Canada.
Int J Food Microbiol. 2020 May 16;321:108550. doi: 10.1016/j.ijfoodmicro.2020.108550. Epub 2020 Feb 5.
Low water activity (a) foods permit the survival of low-infectious dose pathogens including Escherichia coli and Salmonella. Desiccation of non-heat resistant E. coli and Salmonella enterica increases their heat resistance; therefore, alternative methods are necessary to ensure the safety of low a foods. High-pressure carbon dioxide (HPCD) reduced microbial contaminants in high a foods. This study aimed to identify HPCD conditions that reduce pathogenic E. coli and Salmonella in low a conditions. Four strains of Shiga toxin-producing E. coli (STEC) and one strain of enteropathogenic E. coli were treated as a cocktail, and five strains of Salmonella were treated individually. The suitability of E. coli AW1.7, Pediococcus acidilactici FUA 3072, Enterococcus faecium NRRL B-2354 and Staphylococcus carnosus R6 FUA 2133 as surrogate organisms was evaluated. Treatments were validated in beef jerky. Samples were equilibrated to a 0.75 and treated with heat, HPCD or pressurized N. Treatment of desiccated E. coli AW1.7 and the STEC cocktail with dry gaseous CO (5.7 MPa and 65 °C) did not reduce cell counts; however, treatment with gaseous CO saturated with water reduced cell counts of all strains of E. coli. Treatment of beef jerky inoculated with E. coli and Salmonella with saturated gaseous CO resulted in >5-log reductions for all strains. E. faecium NRRL B-2354 and S. carnosus R6 were suitable surrogates for Salmonella on beef jerky treated with HPCD. Treatment of beef jerky with water-saturated gaseous CO was more effective than treatment with supercritical CO or treatments with N at the same temperature and pressure. Overall, the treatment of low a foods with water-saturated gaseous HPCD can meet industry standards by achieving a >5-log reductions of E. coli and Salmonella. Additionally, surrogate organisms representing pathogenic E. coli and Salmonella have been validated.
低水分活度（a）食品允许低传染性剂量病原体（包括大肠杆菌和沙门氏菌）的存活。非耐热型大肠杆菌和肠炎沙门氏菌的干燥会增加其耐热性；因此，需要采用替代方法来确保低水分活度食品的安全性。高压二氧化碳（HPCD）可以减少高水分活度食品中的微生物污染物。本研究旨在确定 HPCD 条件，以减少低水分活度条件下的致病性大肠杆菌和沙门氏菌。将产志贺毒素大肠杆菌（STEC）的四种菌株和一种肠致病性大肠杆菌菌株作为混合物处理，将五种沙门氏菌菌株分别处理。评估了大肠杆菌 AW1.7、戊糖片球菌 FUA 3072、屎肠球菌 NRRL B-2354 和肉葡萄球菌 R6 FUA 2133 作为替代生物的适用性。在牛肉干中验证了处理方法。将样品平衡至 0.75 并进行热处理、HPCD 处理或加压氮气处理。用干燥的气态 CO（5.7 MPa 和 65°C）处理干燥的大肠杆菌 AW1.7 和 STEC 混合物不会降低细胞计数；然而，用饱和水的气态 CO 处理会降低所有大肠杆菌菌株的细胞计数。用饱和气态 CO 处理接种有大肠杆菌和沙门氏菌的牛肉干可使所有菌株的细胞计数减少>5 对数级。在经过 HPCD 处理的牛肉干上，屎肠球菌 NRRL B-2354 和肉葡萄球菌 R6 是沙门氏菌的合适替代物。用饱和气态 CO 处理牛肉干比用超临界 CO 或在相同温度和压力下用氮气处理更有效。总体而言，用饱和气态 HPCD 处理低水分活度食品可以通过实现大肠杆菌和沙门氏菌的>5 对数级减少来达到行业标准。此外，还验证了代表致病性大肠杆菌和沙门氏菌的替代生物。
