Diversity of Microscopic Fungi in the Raw Milk from Latvian Organic Farms

摘要

Raw milk is an ideal growth medium for microorganisms (including many fungal species), as such milk provides all necessary nutrients and conditions for their growth. The objective of the present study was to investigate the diversity of microscopic fungi in the milk obtained in Latvian organic farms depending on cow herd size and season. The study was carried out on 547 milk samples taken from 14 organic dairy farms from December 2011 to November 2012. The farms were divided into three groups according to herd size: small (S - 3-30 cows per shed), medium (M – 31–60 cows per shed), and large (L – 61–120 cows per shed). Milk samples from all four quarters in the same sampling tube were studied. Yeasts and moulds were found in 63.1% and 44.2% of samples, respectively. The identified mould strains belonged to 15 genera - most frequently to Absidia, Aspergillus, Apophysomyces, Mucor, Penicillium, and Rhizopus spp. The highest occurrence of yeasts and moulds was in L herds (73.6% and 50.9%, respectively). Also, milk samples from L herds had the greatest degree of yeast and mould contamination (5.3 and 2.8 log CFU mL-1, respectively). It was found that the occurrence of yeasts was similar by seasons (54.9–68.9%), varying from 5.5 log CFU mL-1 in winter to 2.1–3.3 log CFU mL-1 in other seasons. The occurrence of moulds was the highest in spring (61.6%) and autumn (58.5%), but in winter and summer it was twice lower. The milk samples obtained in winter and summer contained more mould colonies (2.7 and 2.5 log CFU mL-1, respectively) than those obtained in spring and autumn (1.8–1.3 log CFU mL-1, respectively).