Yamaoka H, Nakayama-Imaohji H, Horiuchi I, Yamasaki H, Nagao T, Fujita Y, Maeda H, Goda H, Kuwahara T
Department of Microbiology, Faculty of Medicine, Kagawa University, Kagawa, Japan.
Honbu Sankei Co. Ltd., Chuou-ku, Osaka, Japan.
Lett Appl Microbiol. 2016 Jan;62(1):47-54. doi: 10.1111/lam.12506. Epub 2015 Nov 19.
Chlorine is a principal disinfectant for food and environmental sanitation. Monitoring of free available chlorine (FAC) is essential for ensuring the efficacy of food disinfection processes that rely on chlorine. N,N-diethyl-p-phenylenediamine (DPD) is commonly used for FAC monitoring. However, here, we show that upon contact with bovine serum albumin (BSA) or broiler carcasses, chlorite (HClO2 )-based sanitizers acquire a pink colour, which can interfere with measurement of oxidized DPD absorbance at 513-550 nm. Alternatively, the pink colour did not interfere with 3,3',5,5'-tetramethylbenzidine (TMB)-based FAC monitoring. The FAC levels of NaClO and weakly acidified chlorous acid water (WACAW) were first adjusted by the TMB method and the killing activity of these sanitizers towards methicillin-resistant Staphylococcus aureus (MRSA) and feline calicivirus (FCV) was compared in the presence or absence of 0·5% BSA. At 200 ppm FAC, NaClO lost its bactericidal activity against MRSA after 10-min incubation with 0·5% BSA. Meanwhile, under the same conditions WACAW reduced the number of bacteria to below the detection limit. Similar results were obtained with FCV, indicating that the chlorite-based WACAW sanitizer is relatively stable under organic-matter-rich conditions. Moreover, TMB is suitable for in situ FAC monitoring of chlorite-based sanitizers in food and environmental disinfection processes.
For practical applications of chlorine in food processing, monitoring of FAC is critical to validate disinfection efficacy. In this study we found that chlorite-based sanitizers acquired a pink colour upon contact with BSA or broiler carcasses. This pink colour interfered with FAC monitoring by methods that measure oxidized N,N-diethyl-p-phenylenediamine absorbance between 513-550 nm. Alternatively, FAC levels of chlorite-based sanitizers could be monitored using the absorbance of 3,3',5,5'-tetramethylbenzidine at 650 nm, which does not overlap with the acquired pink colour. These data provide valuable information for safety management of disinfection processes that use chlorite-based sanitizers.
氯是食品和环境卫生的主要消毒剂。监测游离有效氯（FAC）对于确保依赖氯的食品消毒过程的有效性至关重要。N，N-二乙基对苯二胺（DPD）常用于FAC监测。然而，在此我们表明，基于亚氯酸盐（HClO₂）的消毒剂与牛血清白蛋白（BSA）或肉鸡尸体接触后会变成粉红色，这可能会干扰在513 - 550 nm处对氧化DPD吸光度的测量。另外，这种粉红色不会干扰基于3,3',5,5'-四甲基联苯胺（TMB）的FAC监测。首先通过TMB方法调整次氯酸钠（NaClO）和弱酸性亚氯酸水（WACAW）的FAC水平，并比较这些消毒剂在存在或不存在0·5% BSA的情况下对耐甲氧西林金黄色葡萄球菌（MRSA）和猫杯状病毒（FCV）的杀灭活性。在200 ppm FAC时，NaClO与0·5% BSA孵育10分钟后失去了对MRSA的杀菌活性。同时，在相同条件下WACAW将细菌数量减少到检测限以下。FCV也得到了类似的结果，表明基于亚氯酸盐的WACAW消毒剂在富含有机物的条件下相对稳定。此外，TMB适用于食品和环境消毒过程中基于亚氯酸盐的消毒剂的现场FAC监测。
对于氯在食品加工中的实际应用，监测FAC对于验证消毒效果至关重要。在本研究中，我们发现基于亚氯酸盐的消毒剂与BSA或肉鸡尸体接触后会变成粉红色。这种粉红色会干扰通过测量513 - 550 nm之间氧化N，N-二乙基对苯二胺吸光度的方法进行的FAC监测。另外，可以使用3,3',5,5'-四甲基联苯胺在650 nm处的吸光度来监测基于亚氯酸盐的消毒剂的FAC水平，该吸光度与产生的粉红色不重叠。这些数据为使用基于亚氯酸盐的消毒剂的消毒过程的安全管理提供了有价值的信息。
