Microbiological Assessment of Pasteurized Milk in Japan by Different Testing Methods

Hodaka Suzuki^1, , Amalia Widya Rizky Sahoed¹, Rikako Midoh¹ and Yumiko Okada²

¹College of Agriculture, Ibaraki University, Ami, Ibaraki, Japan

²Division of Biomedical Food Research, National Institute of Health Sciences, Kawasaki, Kanagawa, Japan

Cite this paper:
Hodaka Suzuki, Amalia Widya Rizky Sahoed, Rikako Midoh and Yumiko Okada. Microbiological Assessment of Pasteurized Milk in Japan by Different Testing Methods. Journal of Food and Nutrition Research. 2023; 11(3):185-192. doi: 10.12691/jfnr-11-3-3

Abstract

A total of 73 samples of pasteurized milk retailed in Japan, which comprised 47 low-temperature long-time pasteurized samples (LTLT; 63–66°C, 30 min), 13 high-temperature short-time pasteurized samples (HTST; 72–79°C, 15 sec), and 13 high-temperature long-time pasteurized samples (HTLT; 75–85°C, 15–30 min), were analyzed for hygiene indicator microorganisms (standard plate counts [SPCs], coliforms, Enterobacteriaceae, Escherichia coli, and coagulase-positive Staphylococcus aureus) to assess microbiological quality using the Japanese Official Method (JOM), International Standard Organization Methods (ISO), and commercial dehydrated medium sheets. Of the 73 milk samples, one LTLT milk sample was positive for both coliforms and Enterobacteriaceae, and another LTLT milk sample exceeded the Japanese microbiological criterion for the SPC (≤50,000 colony forming units (CFU)/mL). All the samples tested were negative for E. coli and S. aureus. The SPC values obtained using ISO 4833-1:2013 (incubation at 30°C for 72 h) were significantly higher than those obtained using JOM (incubation at 32°C for 48 h); however, a high correlation was observed (R² = 0.7130). In contrast, the correlations between SPCs based on JOM and the two types of dehydrated medium sheets were relatively low (R² = 0.1023 and 0.4046, respectively) although these products obtained third-party certification for analyzing many food products. Our results indicate the importance of verifying alternative methods when new methods are introduced for testing new types or categories of food samples.

Keywords:
dehydrated medium sheet hygiene indicator method comparison pasteurized milk

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