Abstract
A specific rancid and tart off-flavour, probably due to lipolysis of the milk fat, is common in Norwegian goat milk during some seasons. We compared the effects of dietary fat sources on goat milk fat composition and flavour. The experiment was conducted from June to October with 30 animals from the Norwegian Dairy Goat breed. In summer a semi-natural mountain pasture provided roughage, while the animals grazed on a lowland cultivated pasture in the autumn. The goats were fed silage according to appetite indoors for the final 5 weeks of the experiment. The animals were divided into two groups fed different types of concentrate: concentrate A containing sunflower oil (40 g/kg) (mainly C18:1/C18:2) and concentrate B containing 60 g/kg of saturated long chain fatty acids (LCFA) (mainly C16:0/C18:0). Individual milk samples for sensory and chemical analysis were collected in connection with the yield measurements seven times during the experiment (in lactation weeks 10, 14, 16, 17, 19, 22 and 25). The intensity of rancid and tart flavour increased during the mountain grazing period. Milk from goats fed concentrate B (saturated LCFA) showed the lowest ( P<0.05) frequency of rancid taste. No differences ( P>0.05) in the fat, protein and lactose content in the milk were observed between the two groups. Feeding saturated LCFA resulted in less ( P<0.05) ‘goat fatty acids’ (C6:0–C10:0) content and higher ( P<0.05) content of C16 and C18 fatty acids in the milk. It is concluded that supplements with saturated LCFA altered the fatty acid composition in the milk, thereby reducing the frequency of rancid flavours. It appears that the positive effect of supplementation with saturated LCFA was due to a direct effect on the fatty acid composition in the milk. Depression of the ‘goat fatty acids’ C6–C10 could have minimized flavour defects, and a higher content of C16:0 in the milk could have improved the stability of the milk fat globule membrane and thereby decreased the level of lipolysis and off-flavour.
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