Can Fidan O, Demirci Ali, Puri Virendra M, Gourama Hassan
Department of Agricultural and Biological Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
Department of Agricultural and Biological Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, USA; Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
J Food Prot. 2014 Oct;77(10):1723-31. doi: 10.4315/0362-028X.JFP-13-559.
Cheese is a ready-to-eat food that may be contaminated on the surface by undesirable spoilage and pathogenic microorganisms during production, packaging, and postpackaging processes. Penicillium roqueforti is commonly found on cheese surfaces at refrigeration temperatures and is one of the most common spoilage fungal species. Consumption of cheese contaminated with Listeria monocytogenes can result in foodborne listeriosis. Therefore, cheese should be decontaminated at postprocessing stages. Pulsed UV light is a nonthermal method for food preservation that involves the use of intense short pulses to ensure microbial decontamination on the surface of foods or packaging materials. In this study, the efficacy of pulsed UV light for inactivation of P. roqueforti and L. monocytogenes inoculated onto packaged and unpackaged hard cheeses was investigated. Treatment times and the distance from the UV strobe were evaluated to determine optimum treatment conditions. Packaged and unpackaged cheeses were treated at distances of 5, 8, and 13 cm for up to 60 s. For P. roqueforti, maximum reduction after 40 s at 5 cm was 1.32 log CFU/cm(2) on unpackaged cheese and 1.24 log CFU/cm(2) on packaged cheese. Reductions of L. monocytogenes under the same treatment conditions were about 2.9 and 2.8 log CFU/cm(2) on packaged and unpackaged cheeses, respectively. The temperature changes and total energy increases were directly proportional to treatment time and inversely proportional to distance between the UV lamp and the samples. The changes in color and lipid oxidation were determined at mild (5 s at 13 cm), moderate (30 s at 8 cm), and extreme (40 s at 5 cm) treatments. The color and chemical quality of cheeses were not significantly different after mild treatments (P > 0.05). The mechanical properties of the plastic packaging material (polypropylene) also were evaluated after mild, moderate, and extreme treatments. A decreasing trend was noted for elastic modulus; however, no significant differences were found between untreated samples and those given mild and moderate treatments (P > 0.05). Overall, these results indicate that pulsed UV light can inactivate P. roqueforti and L. monocytogenes on the surface of hard cheeses.
奶酪是一种即食食品，在生产、包装及包装后过程中，其表面可能会被不良的腐败微生物和致病微生物污染。在冷藏温度下，干酪青霉通常会出现在奶酪表面，是最常见的腐败真菌种类之一。食用被单核细胞增生李斯特菌污染的奶酪会导致食源性李斯特菌病。因此，奶酪应在加工后阶段进行去污处理。脉冲紫外光是一种用于食品保鲜的非热方法，它利用强烈的短脉冲来确保对食品或包装材料表面进行微生物去污。在本研究中，研究了脉冲紫外光对接种在包装和未包装硬质奶酪上的干酪青霉和单核细胞增生李斯特菌的灭活效果。评估了处理时间和与紫外线闪光灯的距离，以确定最佳处理条件。包装和未包装的奶酪在5厘米、8厘米和13厘米的距离下处理长达60秒。对于干酪青霉，在5厘米处处理40秒后，未包装奶酪上的最大减少量为1.32 log CFU/cm²，包装奶酪上为1.24 log CFU/cm²。在相同处理条件下，包装和未包装奶酪上单核细胞增生李斯特菌的减少量分别约为2.9和2.8 log CFU/cm²。温度变化和总能量增加与处理时间成正比，与紫外线灯和样品之间的距离成反比。在轻度（13厘米处5秒）、中度（8厘米处30秒）和重度（5厘米处40秒）处理下测定了颜色和脂质氧化的变化。轻度处理后奶酪的颜色和化学质量没有显著差异（P > 0.05）。在轻度、中度和重度处理后，还评估了塑料包装材料（聚丙烯）的机械性能。弹性模量呈下降趋势；然而，未处理样品与轻度和中度处理样品之间没有发现显著差异（P > 0.05）。总体而言，这些结果表明脉冲紫外光可以灭活硬质奶酪表面的干酪青霉和单核细胞增生李斯特菌。
