Purpose: The present study aimed to enumerate the total counts of Pseudomonas spp. in raw goat milk, and also their proteolytic colonies, in order to establish their percentage in this food product.
Methods: Sixty-one raw goat milk samples were collected from dairy goat farms located at Zona da Mata region, Minas Gerais State, Brazil, directly from milk cans and bulk tanks. All samples were ten-fold diluted in NaCl 0.85% (w/v) and plated on Pseudomonas agar plates added to sterile skim milk at 10% (v/v). All plates were incubated at 25°C for 3 days when all colonies were enumerated as Pseudomonas spp., and colonies with clear halos were enumerated as proteolytics. Selected proteolytic colonies from all samples were purified and subjected to biochemical tests to identify the genus Pseudomonas.
Results: Considering the obtained counts from Pseudomonas agar, it was observed a mean value of 3.9 log CFU/ml of supposed Pseudomonas, and 3.4 log CFU/ml of proteolytics. The percentages of proteolytic colonies, based on the total counts of Pseudomonas agar, varied from 0 to 100%: 11 samples (18.0%) presented proteolytics colonies at range of 90 to 100%, 7 (11.5%) between 80 to 90%, and 9 (14.8%) between 50 and 80%. A total of 496 proteolytic colonies were subjected to biochemical tests, and 106 were identified as Pseudomonas spp., representing the presence of this genus with proteolytic activity in 33 (54.1%) raw goat milk samples
Significance: The results obtained in the present study indicated the relevance of proteolytic Pseudomonas spp. as constituent of the raw goat milk microbiota, leading to further studies to characterize their proteolytic potential and activity.