DAIRY MANAGEMENT PRACTICES AND THE TRANSMISSION OF ZOONOTIC PATHOGENS IN MILK
Title: Effect of somatic cell count in goat milk on yield, sensory quality and fatty acid profile of semi-hard cheese
Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 9, 2009
Publication Date: April 1, 2010
Citation: Chen, S.X., Wang, J.Z., Van Kessel, J.S., Ren, F.Z., Zeng, S.S. 2010. Effect of somatic cell count in goat milk on yield, sensory quality and fatty acid profile of semi-hard cheese. Journal of Dairy Science. 93(4):1345-1354.
Interpretive Summary: Milk somatic cell count (SCC) is widely used as an indicator for both udder health and milk quality in dairy animals such as cows and goats. An elevated SCC may change the composition of milk. For example, high levels of SCC may decrease casein (protein) and lactose (sugar) levels in cow milk, and therefore affect the yield and quality of cheese that is produced from this milk. Several studies have shown that goat milk has higher SCC than cow milk. This study examined the effect of SCC in milk from goats, that are free from mastitis, on milk and cheese quality. The results showed that milk composition of goats free from mastitis did not differ when milk SCC varied from 250 to 1450 cells/mL, but higher SCC resulted in lower sensory scores for cheeses. Therefore, we concluded that SCC in goat milk can affect the yield of semi-hard cheese, and can result in inferior sensory quality of aged cheeses.
This study investigated the effect of somatic cell count (SCC) of goat milk on yield, free fatty acid (FFA) profile, and sensory quality of semi-hard cheese. Thirty kilograms of goat milk with mean SCC levels of 410,000 (Low), 770,000 (Medium), and 1,250,000 cells/mL (High) was obtained for the manufacture of semi-hard cheese for two consecutive weeks in three lactation stages. The composition of milk was analyzed and cheese yield was recorded on d 1. Cheese samples on d 1, 60, and 120 were analyzed for scores of total sensory, flavor, body/texture, and FFA. Results indicated that the milk composition did not change when milk SCC varied from 214,000 to 1,450,000 cells/mL. Milk with higher SCC had a lower standard plate count while coliform count and psychrotrophic bacteria count were not affected. High SCC milk had a higher pH value. However, milk components (fat, protein, lactose, casein, and total solid) among the three groups were similar. As a result, no significant differences in the yield of semi-hard goat cheeses were detected. However, scores of total sensory and body/texture for cheeses made from the high SCC milk were lower than those from the low and medium SCC milk. The difference in milk SCC levels also resulted in diverse changes in cheese texture (hardness, springiness, etc.) and FFA profiles. Individual and total FFA increased significantly during the ripening, regardless the SCC levels. It is concluded that SCC in goat milk did not affect the yield of semi-hard cheese, but resulted in inferior sensory quality of aged cheeses.