Department of Food Science and Technology, University of Nebraska-Lincoln, NE, USA.
Department of Food Science and Technology, University of Nebraska-Lincoln, NE, USA; Department of Food Science, University of Arkansas-Fayetteville, AR, USA.
Food Microbiol. 2021 Jun;96:103710. doi: 10.1016/j.fm.2020.103710. Epub 2020 Dec 16.
The enhanced heat resistance of Salmonella developed at low water activity makes it a serious challenge to eliminate them during thermal processing. The objectives of this research are to (i) investigate the effect of water activity on thermal inactivation of Salmonella cocktail (Agona, Tennessee, Mbandaka, Montevideo, and Reading) in dried basil leaves, and (ii) evaluate Enterococcus faecium NRRL B-2354 as an appropriate surrogate for Salmonella in dried basil leaves. Dried basil leaves, inoculated with a Salmonella cocktail and E. faecium separately, were equilibrated to different water activities (a: 0.40, 0.55, and 0.70) in a humidity-controlled chamber. The basil samples were packed (1.6 ± 0.1 g) in aluminum pouches and thermally treated at 70, 75, and 80 °C using a dry heating method for 0-180 min to obtain the thermal death curve. The microbial survival data was fit using two primary models (Log-linear and Weibull model). Results from AIC showed that the log-linear model fits well for thermal inactivation of both microorganisms. As the a decreases from 0.70 to 0.40 at 75 °C, the D-value increases from 3.30 to 9.14 min for Salmonella and 6.53 to 14.07 min for E. faecium. Based on the AIC values, the modified Bigelow model fits the D-values better than the response surface model for both the microorganisms. The kill ratio of surrogate to pathogen ranged from 1.4 to 2.8, indicating that it is a conservative surrogate for Salmonella for performing validation of the thermal pasteurization process. The identification of suitable surrogate and development of modified Bigelow model will help the spice industry in developing the thermal processes for improving the safety of basil leaves.
在低水分活度下，沙门氏菌耐热性增强，这使其在热加工过程中难以消除。本研究的目的是：（i）研究水分活度对干燥罗勒叶中沙门氏菌鸡尾酒（阿戈纳、田纳西、姆班达卡、蒙得维的亚和雷丁）热失活动力学的影响；（ii）评估粪肠球菌 NRRL B-2354 作为干燥罗勒叶中沙门氏菌的合适替代物。将接种有沙门氏菌鸡尾酒和粪肠球菌的干燥罗勒叶分别置于湿度可控室中，使其达到不同的水分活度（a：0.40、0.55 和 0.70）。将罗勒叶样品（1.6±0.1g）装入铝袋中，采用干热法在 70、75 和 80°C 下处理 0-180min，获得热死亡曲线。使用两种主要模型（对数线性和 Weibull 模型）拟合微生物存活数据。AIC 的结果表明，对数线性模型很好地适用于两种微生物的热失活动力学。当 75°C 时 a 从 0.70 降低至 0.40 时，沙门氏菌的 D 值从 3.30 增加至 9.14min，粪肠球菌的 D 值从 6.53 增加至 14.07min。根据 AIC 值，对于两种微生物，修正的 Bigelow 模型比响应面模型更适合拟合 D 值。替代物对病原体的杀灭率范围为 1.4 至 2.8，表明替代物是沙门氏菌进行热巴氏杀菌工艺验证的保守替代物。合适替代物的鉴定和修正的 Bigelow 模型的开发将有助于香料行业开发提高罗勒叶安全性的热加工工艺。
