Medycyna Wet. 62 (3), 343-346, 2006
Strzałkowska N., Bagnicka E., JóźŸwik A., ŚŒliwa-JóźŸwik A., Krzyżewski J.
Relationship between the number of lipolytic bacteria, season of the year, and susceptibility of goat milk to lipolysis
The aim of this study was to establish the relationship between the number of lipolytic bacteria, the season of the year, and susceptibility of goat milk fat to lipolysis. The study was carried out on 60 Polish White Improved goats. The animals were divided into two groups (30 goats in each) according to the number of lactations. Goats were maintained in pens and fed diets according to the INRA-system. Milk samples were taken once a month and analysed for fat, total protein and lactose content and somatic cell count. Moreover, each milk sample was analysed for the number of lipolytic bacteria and free fatty acids (FFA) immediately after milking and subsequently after 72 hours (storage in temperature 4°C). The levels of FFA in milk directly after milking in each season of the year were almost equal (the differences were insignificant). However after 72 hours the concentration of FFA tripled during the spring and the summer, while during the autumn the increase of level of FFA was negligible in comparison to the level at milking time. In the stored milk samples the number of lipolytic bacteria increased 460, 70 and 6-fold during the spring, the summer and the autumn, respectively. The obtained results indicate that there is no strong relationship between the increase of the number of lipolytic bacteria and the level of FFA. In the milk from primiparous goats the number of psychrotrophic bacteria and the level of FFA was significantly lower in comparison to milk of goats in the 2nd lactation. The authors suggest the need for further investigations concerning the identification of individual strains of lipolytic bacteria, proliferate rate and scale of lipolysis of fat in goat’s milk during storage at 4°C.
Keywords: goat, milk, lipolytic bacteria