Submitted to: Journal of Food Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/2/2007
Publication Date: 3/2/2007
Citation: Van Hekken, D.L., Tunick, M.H., Soryal, K.A., Zeng, S.S. 2007. Proteolytic and rheological properties of aging cheddar-like caprine milk cheeses manufactured at different times during lactation. Journal of Food Science. 72:(3):E115-E120. Interpretive Summary: The manufacture of goat's milk cheese is a growing industry in the United States that is challenged by seasonal milk supply. Goats are milked from early spring to the fall. Many factors in milk change throughout the milking cycle making it difficult to produce high quality cheeses that age well. In this study, we evaluated the impact of the milking cycle on the texture of goat's milk cheeses by measuring the response of the cheese to various applied stresses and strains. Hard Cheddar-like cheeses were manufactured using milk from three distinct stages of the milking cycle (early, middle, and late) and were aged for up to 24 weeks. Results showed that although the milk composition was about constant over the entire milking cycle, the texture of cheeses made within the first and the last month of the milking cycle had lower values of texture than cheeses made in the middle of the milking cycle. This suggests that the ability of the component proteins to interact was altered as the milking cycle progressed influencing the structure of the cheese matrix. Cheese manufacturers need to be mindful of the stage of lactation of their cheesemilk and shift milk from too early or too late in the milking cycle to other dairy products that are less affected by this factor.
Technical Abstract: The effects of using caprine milk collected at different stages of lactation on the compositional, proteolytic, and rheological properties of hard cheeses were evaluated over 24 wk of aging. Multiple batches of Cheddar cheese were made using whole milk from Alpine goats at early, peak, or late stages of their lactation cycles, approximately 4 to 5, 12 to 15, and 21 to 23 wk after parturition, respectively. The composition of cheesemilk and resulting Cheddar-like cheeses did not vary significantly as lactation progressed although all cheeses contained less than the fat levels required to be labeled Cheddar. Proteolytic and rheological properties of the cheeses were measured within 1 wk of being manufactured and after 8, 16, and 24 wk of aging at 4 deg C. The rheological properties of caprine milk Cheddar-like cheeses were influenced by the higher degree of proteolysis found in cheeses made at the onset and near the termination of lactation. Cheeses made from milk collected during the peak of lactation were the most uniform and had the firmest and least flexible protein matrix (highest values for hardness, chewiness, shear rigidity at point of fracture, elastic and viscous moduli, and complex viscosity). The stage of lactation does influence the rheology of cheeses made from milk at different stages of lactation and, in the manufacture of hard cheeses such as Cheddar, the use of cheesemilk from too early or late in the cycle should be minimized to maintain high quality and uniform caprine milk cheeses.