Changes in goat milk composition during lactation and their effect on yield and quality of hard and semi-hard cheeses

Bulk tank goat milk from the Langston University Alpine herd was used to investigate changes in composition of goat milk during lactation and their effects on the sensory quality and yield of hard and semi-hard cheeses. Milk was analyzed for fat, protein, casein, total solids and somatic cell count (SCC) and cheese was assayed for of fat, protein and moisture. Sensory evaluation of the cheeses was performed to establish the relationship between yield, quality and sensory score. The chemical composition of goat milk changed significantly over lactation, resulting in variation in yield and sensory quality of hard and semi-hard cheeses. While casein content of goat milk did not change significantly as lactation advanced, SCC increased from early to late lactation. There were no significant differences in flavor, body and texture, and total sensory scores of either cheese type among aging times of 8, 16 and/or 24 week, which indicates that the cheeses can be consumed after 8 week for similar sensory quality as with longer aging. In hard cheese, yield was highly correlated with milk fat, protein or total solids, whereas only milk total solids content was highly correlated with semi-hard cheese yield. These findings indicate need to adjust cheese making procedures over the duration of lactation to increase milk nutrient recoveries and thus increase cheese yield. However, a year-round breeding system should minimize variation in chemical composition in bulk tank goat milk during lactation and help maintain consistent quality and yield of cheeses throughout the year.