2018 Volume 35 Issue 4 Pages 179-186
The automatic ATP measurement system was applied to rapid test for coliforms in milk and yogurt. The methods by bioluminescence assay after selective enrichment culture were evaluated, and following results were obtained. When a bioluminescence assay was applied to detect coliforms after BGLB enrichment, the results were affected by ATP derived from lactic acid bacteria. Conversely, dLST (LST with sodium deoxycholate) or nBGLB (BGLB with nisin) enrichment was able to minimize the influence of lactic acid bacteria. Because preparation of dLST was easier than nBGLB, it was concluded that dLST is the most suitable enrichment broth for use in detecting coliforms in yogurt by bioluminescence assay. The dLST-ATP method with an automatic ATP measurement system after eight hours dLST enrichment was able to detect 1–10 cfu/mL levels of coliforms in milk and 1–10 cfu/0.1 g levels of coliforms in yogurt. Inclusivity of the dLST-ATP method as a presumptive coliforms test is 100.0%, and exclusivity is 90.3%. The results of the comparative study showed that there was a significant correlation between the dLST-ATP method and the BGLB method, and the desoxycholate agar method. The dLST-ATP method takes only about eight hours for presumptive coliforms test, and the method is simple and can be used not only for milk samples but also yogurt samples. Considering these results, the dLST-ATP method should be useful as a rapid test for coliforms in milk and yogurt.