Food Safety and Intervention Technologies Research Unit, Eastern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, 600 East Mermaid Lane, Wyndmoor, PA 19038, USA.
Int J Food Microbiol. 2013 Mar 1;162(1):43-7. doi: 10.1016/j.ijfoodmicro.2012.12.005. Epub 2012 Dec 23.
Studies are limited on UV nonthermal pasteurization of liquid egg white (LEW). The objective of this study was to inactivate Escherichia coli using a UV irradiator that centrifugally formed a thin film of LEW on the inside of a rotating cylinder. The LEW was inoculated with E. coli K12 to approximately 8 log cfu/ml and was processed at the following conditions: UV intensity 1.5 to 9.0 mW/cm²; cylinder rotational speed 450 to 750 RPM, cylinder inclination angle 15° to 45°, and flow rate 300 to 900 ml/min, and treatment time 1.1 to 3.2s. Appropriate dilutions of the samples were pourplated with tryptic soy agar (TSA). Sublethal injury was determined using TSA+4% NaCl. The regrowth of surviving E. coli during refrigerated storage for 28 days was investigated. The electrical energy of the UV process was also determined. The results demonstrated that UV processing of LEW at a dose of 29 mJ/cm² at 10°C reduced E. coli by 5 log cfu/ml. Inactivation significantly increased with increasing UV dose and decreasing flow rate. The results at cylinder inclination angles of 30° and 45° were similar and were significantly better than those at 15°. The cylinder rotational speed had no significant effect on inactivation. The occurrence of sublethal injury was detected. Storage of UV processed LEW at 4° and 10°C for 21 days further reduced the population of E. coli to approximately 1 log cfu/ml where it remained for an additional 7 days. The UV energy applied to the LEW to obtain a 5 log reduction of E. coli was 3.9 J/ml. These results suggest that LEW may be efficiently pasteurized, albeit at low flow rates, using a nonthermal UV device that centrifugally forms a thin film.
关于液态蛋清（LEW）的非热紫外线巴氏杀菌研究有限。本研究的目的是使用紫外线辐照器来灭活大肠杆菌，该辐照器在旋转圆筒的内部将 LEW 离心形成一层薄膜。将 LEW 接种大肠杆菌 K12，使其达到约 8 log cfu/ml，并在以下条件下进行处理：UV 强度为 1.5 至 9.0 mW/cm²；圆筒旋转速度为 450 至 750 RPM，圆筒倾斜角度为 15°至 45°，流速为 300 至 900 ml/min，处理时间为 1.1 至 3.2s。适当稀释样品后，用胰蛋白酶大豆琼脂（TSA）倾注平板。使用 TSA+4%NaCl 确定亚致死损伤。研究了在 28 天冷藏储存期间幸存大肠杆菌的再生情况。还确定了紫外线处理过程的电能。结果表明，在 10°C 下，LEW 经 29 mJ/cm² 的紫外线剂量处理可使大肠杆菌减少 5 log cfu/ml。随着紫外线剂量的增加和流速的降低，失活显著增加。在 30°和 45°的圆筒倾斜角下的结果相似，且明显优于 15°的结果。圆筒旋转速度对失活没有显著影响。检测到亚致死损伤的发生。将经紫外线处理的 LEW 在 4°C 和 10°C 下储存 21 天，可使大肠杆菌的数量进一步减少到约 1 log cfu/ml，并在额外的 7 天内保持不变。将 LEW 用于获得大肠杆菌 5 log 减少所需的紫外线能量为 3.9 J/ml。这些结果表明，尽管流速较低，但使用离心形成薄膜的非热紫外线装置可以有效地对 LEW 进行巴氏杀菌。
