مشخصات پژوهش

The quality and hygienic status of milk are of importance for both dairy industries and consumers. In the present study, the effect of season on the quality and microbial properties of sheep milk and yoghurt produced from sheep milk were surveyed. In total, 30 sheep-milk samples were collected from January to August 2011, and yoghurt was produced from these samples. The fat content, titratable acidity and pH showed changes across the year. Seasonal variation was found to have a significant (P < 0.05) effect on nitrogen components, particularly crude protein, non-casein protein and non-protein nitrogen contents, fat content, pH and titratable acidity. Sensory analysis showed that the quality of yoghurt samples produced in winter was higher than that of yoghurt produced in summer (P< 0.05). This work showed the effect of season on chemical and sensory properties of sheep milk and yoghurt in Qazvin, Iran.