Yang Ren, Zhang Shuang, Tang Juming
Department of Agricultural and Biosystems Engineering, South Dakota State University, P.O. Box 2100, SRPA-136, Brookings, SD 57007, USA.
Department of Biological Systems Engineering, Washington State University, P.O. Box 646120, Pullman, WA 99164, USA.
Foods. 2024 Nov 30;13(23):3877. doi: 10.3390/foods13233877.
Drying is one of the most effective preservation methods for extending the shelf-life of perishable foods. The microbial safety of low-moisture food products had not been recognized as a concern until outbreaks reported over the past decade in products contaminated with bacterial pathogens, in particular . There is now an urgent need to understand the influence of process conditions on the thermal inactivation of pathogens in various drying operations. This study aimed to develop a predictive model for inactivation in diced apples during hot air drying and in high-humidity heating in closed environments. Fresh-cut apple cubes (6 mm) inoculated with a cocktail of strains (Enteritidis PT30, Montevideo 488275, and Agona 447967) were placed in a customized box inside an oven for three different treatments: (1) open-box drying at oven temperature 90 °C (Drying-90); (2) close-box pre-drying heating at 90 °C (PD heating-90); and (3) close-box pre-drying heating at 70 °C (PD heating-70). Air temperature, relative humidity (RH), and sample temperatures were monitored, and survival was measured at multiple time intervals. After 10 min, the air RH reached 66% in PD heating-90 and 74% in PD heating-70, versus 30% in Drying-90. A 5-log reduction in was achieved in 8.5 min in PD heating-90, and 14 min in PD heating-70, compared to 28.7 min in Drying-90. A mathematical model using sample surface RH and sample temperature profiles accurately predicted inactivation across all treatments (RMSE = 0.92 log CFU/g, R = 0.86), with thermal death parameters comparable to isothermal studies. This study underscores the role of humidity in enhancing microbial reduction during drying and proposes high-humidity pre-drying heating as an effective control step. The developed model shows promise for real-time prediction of microbial inactivation in complex drying environments with dynamic temperature and humidity conditions.
干燥是延长易腐食品保质期最有效的保存方法之一。直到过去十年报道了受细菌病原体污染的产品爆发疫情后，低水分食品的微生物安全性才受到关注，尤其是。现在迫切需要了解加工条件对各种干燥操作中病原体热失活的影响。本研究旨在建立一个预测模型，用于预测在热风干燥和封闭环境中的高湿度加热过程中，切块苹果中病原体的失活情况。将接种了三种菌株（肠炎沙门氏菌PT30、蒙得维的亚488275和阿哥纳447967）混合菌液的新鲜切块苹果立方体（6毫米）放入烤箱内定制的盒子中进行三种不同处理：（1）在烤箱温度90°C下开箱干燥（干燥-90）；（2）在90°C下闭箱预干燥加热（PD加热-90）；（3）在70°C下闭箱预干燥加热（PD加热-70）。监测空气温度、相对湿度（RH）和样品温度，并在多个时间间隔测量病原体存活率。10分钟后，PD加热-90中的空气RH达到66%，PD加热-70中的空气RH达到74%，而干燥-90中的空气RH为30%。与干燥-90中的28.7分钟相比，PD加热-90在8.5分钟内实现了病原体5个对数级的减少，PD加热-70在14分钟内实现了病原体5个对数级的减少。使用样品表面RH和样品温度曲线的数学模型准确预测了所有处理中的病原体失活情况（均方根误差=0.92 log CFU/g，R=0.86），热死亡参数与等温研究相当。本研究强调了湿度在干燥过程中增强微生物减少方面的作用，并提出高湿度预干燥加热作为一种有效的控制步骤。所开发的模型显示出在动态温度和湿度条件下的复杂干燥环境中实时预测微生物失活的潜力。
