Laboratory of Food Microbiology and Hygiene, College of Home Economics, Alonso Hall, College of Home Economics, Antonio Ma. Regidor St., University of the Philippines Diliman, Quezon City, 1101, Philippines.
Laboratory of Food Microbiology and Hygiene, College of Home Economics, Alonso Hall, College of Home Economics, Antonio Ma. Regidor St., University of the Philippines Diliman, Quezon City, 1101, Philippines.
Int J Food Microbiol. 2018 Jul 20;277:64-73. doi: 10.1016/j.ijfoodmicro.2018.04.019. Epub 2018 Apr 14.
This study determined the inactivation kinetic parameters of selected pathogens in heat, ultraviolet-C and combined heat-UV-C treated coconut liquid endosperm. Separate cocktails of Escherichia coli O157:H7, Salmonella enterica serovars, and Listeria monocytogenes strains were inoculated into coconut liquid endosperm (pH 5.15, TSS 4.4Bx, TA 0.062% malic acid, extinction coefficient (ε) at 254 nm of 0.0154 cm) for inactivation studies. Result showed that all organisms generally exhibited a log-linear heat inactivation behavior (R 0.81-0.99). The E. coli O157:H7 cocktail (D = 19.75 min, D = 10.79 min, D = 3.38 min, and D = 0.46 min) was found to be significantly more resistant (P > 0.05) than the tested cocktail of L. monocytogenes (D = 11.68 min, D = 4.53 min, D = 1.82 min and D = 0.26 min) and S. enterica cocktail (D = 3.08 min, D = 2.60 min, D = 0.89 min and D = 0.25 min). Despite the differences in D values, computed z values for L. monocytogenes cocktail (5.12 ± 0.43 °C) and E. coli O157:H7 cocktail (4.95 ± 0.12 °C) were not significantly different (P > 0.05), but were both significantly (P < 0.05) lower than that of S. enterica cocktail (7.10 ± 0.15 °C). All test organisms also exhibited a generally log-linear UV-C inactivation behavior (R 0.90-0.99) with E. coli O157:H7 cocktail (D = 25.26 mJ/cm) demonstrating greatest resistance to UV-C than S. enterica (D = 24.65 mJ/cm) and L. monocytogenes (D = 17.30 mJ/cm) cocktails. The D values of each organism cocktail were used to calculate for the 3-log reduction heating process schedules, during which UV-C treatments were simultaneously applied. Lethal rates (F values) calculations in the combined processes revealed that within the 3-log reduction heating processes, co-exposure of UV-C resulted in 5.62 to 6.20 log reductions in the test organism populations. Heating caused 69.3, 97.2, and 67.4% of the reduction in E. coli O157:H7, S. enterica and L. monocytogenes cocktails, respectively. These results can be used as baseline data in the establishment of mild heat treatment in combination with UV-C process schedules for coconut liquid endosperm and other similar products.
本研究确定了选定病原体在热、紫外线-C 和热-紫外线-C 联合处理椰子液体胚乳中的失活动力学参数。分别将大肠杆菌 O157:H7、沙门氏菌血清型和单核细胞增生李斯特菌菌株的鸡尾酒接种到椰子液体胚乳中（pH 5.15、TSS 4.4Bx、TA 0.062% 苹果酸、254nm 处的消光系数 (ε) 为 0.0154cm）进行失活研究。结果表明，所有生物体通常表现出对数线性热失活动力学行为（R 0.81-0.99）。大肠杆菌 O157:H7 鸡尾酒（D=19.75min，D=10.79min，D=3.38min，D=0.46min）被发现比测试的李斯特菌鸡尾酒（D=11.68min，D=4.53min，D=1.82min，D=0.26min）和沙门氏菌鸡尾酒（D=3.08min，D=2.60min，D=0.89min，D=0.25min）具有更高的抗性（P>0.05）。尽管 D 值存在差异，但李斯特菌鸡尾酒（5.12±0.43°C）和大肠杆菌 O157:H7 鸡尾酒（4.95±0.12°C）的计算 z 值没有显著差异（P>0.05），但均明显低于沙门氏菌鸡尾酒（7.10±0.15°C）（P<0.05）。所有测试的生物体也表现出通常的对数线性紫外线-C 失活动力学行为（R 0.90-0.99），其中大肠杆菌 O157:H7 鸡尾酒（D=25.26mJ/cm）对紫外线-C 的抵抗力最大，大于沙门氏菌（D=24.65mJ/cm）和单核细胞增生李斯特菌（D=17.30mJ/cm）鸡尾酒。使用每个生物体鸡尾酒的 D 值来计算 3 对数减少加热过程计划，在此期间同时应用紫外线-C 处理。在联合处理中的致死率（F 值）计算表明，在 3 对数减少加热过程中，紫外线-C 的共同暴露导致测试生物体种群减少了 5.62 至 6.20 对数。加热导致大肠杆菌 O157:H7、沙门氏菌和单核细胞增生李斯特菌鸡尾酒分别减少了 69.3%、97.2%和 67.4%。这些结果可作为建立椰子液体胚乳和其他类似产品温和热处理与紫外线-C 工艺计划相结合的基础数据。
