Randriamiarintsoa Narindra, Ryser Elliot T, Marks Bradley P
Department of Biosystems and Agricultural Engineering, Michigan State University, East Lansing, MI 48824, USA.
Department of Food Science and Human Nutrition, Michigan State University, East Lansing, MI 48824, USA.
J Food Prot. 2024 Apr;87(4):100253. doi: 10.1016/j.jfp.2024.100253. Epub 2024 Feb 28.
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 (a), 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.
工业上使用多种干燥参数和方法来生产苹果干。为确保最终产品安全并符合法规要求，评估此类工业操作对微生物灭活的有效性至关重要。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菌灭活的影响。选用嘎啦苹果去核后切成环状薄片（约6毫米厚），用单核细胞增生李斯特菌8菌株混合菌液的肉汤培养物进行表面接种，使接种水平达到8.6±0.3 log CFU/g。苹果环在中试规模的冲击式烘箱中分批干燥，干燥空气温度为60或80℃，空气流速为0.7或2.1米/秒，每30分钟取样进行细菌计数、水分活度（a）和水分含量分析。单核细胞增生李斯特菌的减少量随着空气流速的增加或干燥空气温度的升高而增加（P<0.05）。在干燥结束时，达到了苹果干片湿基标准水分含量<24%，在60℃下干燥180分钟后，空气流速为0.7和2.1米/秒时，单核细胞增生李斯特菌分别减少了1.8±0.3和2.8±0.7 log CFU/g。当使用80℃干燥温度时，150分钟后两种空气流速下单核细胞增生李斯特菌的减少量均为5.2±0.5 log CFU/g。因此，在水果干燥过程的验证中应考虑工艺条件，而不是仅仅依赖于产品的最终特性，如水分含量。
