Mizuochi Shingo, Nelson Maria, Baylis Chris, Jewell Keith, Green Becky, Limbum Rob, Fernandez Maria Cristina, Salfinger Yvonne, Chen Yi
Nissui Pharmaceutical Co., Ltd, 3-23-9, Ueno, Taito-ku, Tokyo 110-8736, Japan.
Nelson Consulting, Savage, MN 8637 Carriage Hill Ct. Savage, MN 55378, USA.
J AOAC Int. 2016 Mar-Apr;99(2):461-8. doi: 10.5740/jaoacint.15-0267. Epub 2016 Mar 10.
A validation study was conducted to extend the matrix claim for the Nissui Compact Dry Total Count (TC), Performance Tested Method(s)(SM) (PTM) Certification No. 010404, to cooked chicken, lettuce, frozen fish, milk powder, and pasteurized whole milk. The method was originally certified by the AOAC Research Institute Performance Tested Method(s)(SM) Program for raw meat products. The Compact Dry TC is a ready-to-use dry media sheet that is rehydrated by adding 1 mL of diluted sample. A total aerobic colony count can be determined in the sample following 48 h of incubation. Matrix extension studies were conducted by Campden BRI (formerly Campden and Chorleywood Food Research Association Technology Limited), Chipping Campden, UK. Single-laboratory data were collected for cooked chicken, lettuce, frozen fish, and milk powder, whereas a multilaboratory study was conducted on pasteurized milk. Fourteen laboratories participated in the collaborative study. The Compact Dry TC was tested at two time points, 48 ± 3 h and 72 ± 3 h and compared with the current International Organization for Standardization (ISO) method at the time of the study, ISO 4833:2003 (this standard is withdrawn and has been replaced by: ISO 4833-1:2013 and ISO 4833-2:2013), Microbiology of food and animal feeding stuffs-Horizontal method for the enumeration of microorganisms-Colony-count technique at 30°C. The data were logarithmically transformed and evaluated for repeatability (plus reproducibility for pasteurized milk), RSD of repeatability (plus RSD of reproducibility for milk), r(2), and mean difference between methods with 95% confidence interval (CI). A CI outside of (-0.5 to 0.5) on the log10 mean difference was used as the criterion to establish significant statistical difference between methods. No significant differences were found between the Compact Dry TC 48 and 72 h time points, with the exception of one contamination level of cooked chicken and one contamination level of dry milk powder. Mean differences were small at these levels (<0.5 log10), but the upper CIs were above 0.5. Statistical differences were indicated between the Compact Dry TC and ISO 4833 in two of five contamination levels tested each for lettuce and frozen fish. In each case, mean differences were >0.5 log10, and the total aerobic colony count was higher for the ISO method. In most cases, mean differences between the Compact Dry and ISO methods were small (<0.5 log10) with CIs within the acceptance criterion. Repeatability, reproducibility, and RSD were similar for both methods, and r(2) values were >0.97 for all matrixes. The Compact Dry TC, at 48 h, offers the advantage of a shorter time to results than ISO 4833 in an easy-to-use format.
进行了一项验证研究，以将日水紧凑型干式总菌数（TC）的基质声明扩展至熟鸡肉、生菜、冷冻鱼、奶粉和巴氏杀菌全脂牛奶，该产品的性能测试方法（SM）认证编号为010404。该方法最初由AOAC研究机构性能测试方法（SM）计划针对生肉产品进行认证。紧凑型干式TC是一种即用型干燥培养基片，通过加入1 mL稀释样品进行复水。在培养48小时后可测定样品中的总需氧菌落数。基质扩展研究由英国奇平卡姆登的坎普登BRI（原坎普登和乔利伍德食品研究协会技术有限公司）进行。收集了熟鸡肉、生菜、冷冻鱼和奶粉的单实验室数据，而对巴氏杀菌牛奶进行了多实验室研究。14个实验室参与了协作研究。在48±3小时和72±3小时两个时间点对紧凑型干式TC进行测试，并与研究时现行的国际标准化组织（ISO）方法ISO 4833:2003（该标准已废止，已被ISO 4833-1:2013和ISO 4833-2:2013取代）进行比较，该方法为食品和动物饲料微生物学——30°C下微生物计数的水平方法——菌落计数技术。数据进行对数转换，并评估重复性（巴氏杀菌牛奶为再现性）、重复性相对标准偏差（牛奶为再现性相对标准偏差）、r(2)以及方法之间具有95%置信区间（CI）的平均差异。以log10平均差异的CI在（-0.5至0.5）之外作为确定方法之间存在显著统计差异的标准。除了一个熟鸡肉污染水平和一个奶粉污染水平外，在紧凑型干式TC的48小时和72小时时间点未发现显著差异。这些水平下的平均差异较小（<0.5 log10），但上限CI高于0.5。在测试的生菜和冷冻鱼的五个污染水平中的两个水平上，紧凑型干式TC与ISO 4833之间存在统计差异。在每种情况下，平均差异>0.5 log10，且ISO方法的总需氧菌落数更高。在大多数情况下，紧凑型干式方法与ISO方法之间的平均差异较小（<0.5 log10），CI在接受标准范围内。两种方法的重复性、再现性和相对标准偏差相似，所有基质的r(2)值均>0.97。48小时的紧凑型干式TC具有比ISO 4833更快得出结果的优势，且格式易于使用。
