Abstract：
A wide range of drying parameters and methods are used by industry to produce dried apples. To ensure end-product safety and regulatory compliance, it is essential to evaluate the effectiveness of such industrial practices on microbial inactivation. Therefore, the objective of this study was to evaluate the effects of drying air temperature and velocity on Listeria monocytogenes inactivation during drying of apple slices. Apples (cv. Gala) were cored, sliced as rings (∼6 mm thick), and surface-inoculated with broth-grown culture of an 8-strain cocktail of L. monocytogenes to achieve an inoculation level of 8.6 ± 0.3 log CFU/g. Apple rings were dried in batches using dry air in a pilot-scale impingement oven at 60 or 80 °C air temperature and 0.7 or 2.1 m/s air velocity, and sampled every 30 min for bacterial enumeration, water activity (aw), and moisture content analysis. L. monocytogenes reduction increased (P < 0.05) with higher air velocity or higher drying air temperature. By the end of drying, in which the standard moisture content for dried apple slices of <24% wet basis was reached, L. monocytogenes was reduced by 1.8 ± 0.3 and 2.8 ± 0.7 log CFU/g at 0.7 and 2.1 m/s air velocity, respectively, after 180 min at 60 °C. When using 80 °C drying temperature, L. monocytogenes reduction was 5.2 ± 0.5 log CFU/g at both air velocities after 150 min. Therefore, process conditions should be considered in the validation of fruit drying processes, instead of solely relying on product endpoint properties, such as moisture content.
摘要：
工业上使用多种干燥参数和方法来生产干苹果。为了确保最终产品的安全性和合规性，必须评估此类工业实践对微生物灭活的有效性。因此,本研究的目的是评估干燥空气温度和速度对苹果片干燥过程中单核细胞增生李斯特氏菌失活的影响。苹果（简历。Gala)werecorred,切成环（〜6毫米厚），并用8株单核细胞增生李斯特菌混合物的肉汤培养培养物进行表面接种，以达到8.6±0.3logCFU/g的接种水平。在60或80°C的空气温度和0.7或2.1m/s的空气速度下，在中试规模的冲击烘箱中使用干燥空气分批干燥苹果环，每30分钟取样进行细菌计数，水活度(AW)，和水分含量分析。随着空气速度的增加或干燥空气温度的升高，单核细胞增生李斯特菌的减少增加（P<0.05）。在干燥结束时,其中达到<24%湿基的干苹果片的标准水分含量，在0.7和2.1m/s的空气速度下，单核细胞增生性杆菌减少了1.8±0.3和2.8±0.7logCFU/g，分别,在60°C下180分钟后当使用80°C干燥温度时，150分钟后，在两种空气速度下，单核细胞增生性李斯特菌的减少量为5.2±0.5logCFU/g。因此,在验证水果干燥过程时应考虑工艺条件，而不是仅仅依赖产品端点属性，如水分含量。
