Microbiological quality of raw milk produced in Estonia

Abstract

Aims: The microbial quality of farm bulk-tank raw milk produced in Estonia during years 2004-2007 was investigated.

Methods and results: Bulk-tank milk samples were analysed for lactic acid bacteria count (LABC), psychrotrophic bacteria count (PBC), aerobic spore-forming bacteria count (ASFBC), total bacterial counts using BactoScan and somatic cell count (SCC) using Fossomatic. Randomly selected psychrotrophic isolates were subjected to 16S-23S PCR-ribotyping. LABC remained below 10(4) CFU ml(-1) in most samples, while psychrotrophic micro-organisms dominated in 60% of farms. PBC ranged from 4.2 × 10(2) to 6.4 × 10(4) CFU ml(-1), and ASFBC varied from 5 to 836 CFU ml(-1).

Conclusions: In general, the microbiological quality of the farm bulk-tank milk was good - more than 91% of samples contained <50,000 CFU ml(-1), and SCC in the majority of samples did not exceed the internationally recommended limits. Genus Pseudomonas spp. was the dominating spoilage flora with Pseudomonas fluorescens as the prevailing species.

Significance and impact of the study: Specific bacterial groups (LABC, PBC and ASFBC), not analysed routinely by dairies, were determined in bulk-tank raw milk of numerous dairy farms during 4-year period. Based on the survey, dairy plants can better control their supply chains and select farms (milk) for the production of specific products, i.e. milk with low PBC and high LABC for cheesemaking.