Mahmoud N S, Ghaly A E
Biological Engineering Department, Dalhousie University, P.O. Box 1000, Halifax, Nova Scotia, Canada.
Biotechnol Prog. 2004 Mar-Apr;20(2):550-60. doi: 10.1021/bp030050i.
The effectiveness of ultraviolet radiation for on-line sterilization of cheese whey was investigated. The effects of flow rate and residence time on the performance of three UV reactors having different gap sizes (18, 13, and 6 mm) were studied. Six flow rates and six residence times were tested with the three UV reactors. The cheese whey used in this study had a very high turbidity (4317 NTU), very poor transmittance in the UV radiation germicidal range ( approximately 0%), and high percentage of large solid particles ( approximately 20% > 100 microm). Although the cheese whey physical characteristics showed low probability of sterilization using UV radiation, the study showed that UV radiation can be used on-line to sterilize cheese whey if the proper reactor gap size and the appropriate residence time are used. There were combined effects of the flow rate and gap size. The cell removal efficiency increased with increases in residence time and decreases in the UV reactor gap size. Removal efficiency of 100% was not achieved in this study with the first UV reactor (18-mm gap size), whereas 100% removal efficiency was achieved with the second (13-mm gap size) and third (6-mm gap size) UV reactors at residence times of 2.0 and 0.5 h, respectively. The microbial decay rates achieved in this study were 4.94, 7.62, and 20.9 h(-)(1) using the first, second, and third UV reactor, respectively. Residence times of 3.3, 2.1, and 0.8 h would be required to completely destruct a microbial population of 5.95 x 10(6) cells/mL using the first, second, and third UV reactors, respectively. Although cheese whey sterilization using UV radiation seems to be a good alternative to pasteurization, increases in cheese whey temperature resulted in lamp fouling. If online sterilization is to be used, the fouling problem should be investigated and a maintenance scheme for the UV reactor should be developed.
研究了紫外线对奶酪乳清进行在线杀菌的有效性。研究了流速和停留时间对三种不同间隙尺寸（18毫米、13毫米和6毫米）的紫外线反应器性能的影响。使用这三种紫外线反应器测试了六种流速和六种停留时间。本研究中使用的奶酪乳清浊度非常高（4317 NTU），在紫外线杀菌范围内的透光率非常低（约0%），大固体颗粒的百分比很高（约20%>100微米）。尽管奶酪乳清的物理特性表明使用紫外线杀菌的可能性较低，但研究表明，如果使用合适的反应器间隙尺寸和适当的停留时间，紫外线可用于在线对奶酪乳清进行杀菌。流速和间隙尺寸存在综合影响。细胞去除效率随着停留时间的增加和紫外线反应器间隙尺寸的减小而提高。在本研究中，第一个紫外线反应器（间隙尺寸18毫米）未实现100%的去除效率，而第二个（间隙尺寸13毫米）和第三个（间隙尺寸6毫米）紫外线反应器分别在停留时间为2.0小时和0.5小时时实现了100%的去除效率。本研究中使用第一、第二和第三个紫外线反应器实现的微生物衰减率分别为4.94、7.62和20.9 h⁻¹。使用第一、第二和第三个紫外线反应器分别需要3.3小时、2.1小时和0.8小时的停留时间才能完全消灭5.95×10⁶个细胞/毫升的微生物群体。尽管使用紫外线对奶酪乳清进行杀菌似乎是巴氏杀菌的一个很好的替代方法，但奶酪乳清温度的升高会导致灯污损。如果要使用在线杀菌，应研究污损问题并制定紫外线反应器的维护方案
