Abstract
Standard samples were prepared for this study, and applied for BactoScanTM and BactoCountTM in order for quality control evaluation for total bacterial count in raw milk. Accordingly, the preparation of two lots of standard samples for quality control were lyophilized, which contain Lactobacillus lactis. The standard samples were prepared into three different levels of bacterial counts, those were Low 30,000~40,000, Medium 70,000~90,000, High 150,000~220,000 CFU/mL, respectively. Then, the proficiency tests were performed in total 19 laboratories for measuring total bacterial counts. The total bacterial counts in the standard samples showed 37~42, 82~105, 214~240 CFU/mL in the first lot, and it showed 30~36, 67~75, 131~163 CFU/mL in the second lot in low, medium and high levels, respectively. Based on these results, the absolute values of z-scores of six standard samples in 18 laboratories were ≤2, which means the samples are satisfactory. However, z-score in one laboratory was ≤3, which means the sample is questionable. Using two standard samples, the correlation between BactoScanTM and BactoCountTM was 0.9982, which means the results of total bacterial count measurement of both equipment were equivalent. Therefore, the standard samples manufactured in this study for quality control of total bacterial count using BactoScanTM and BactoCountTM in the raw milk could be applied to proficiency tests.
