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Title: EFFECT OF FROZEN STORAGE ON PROTEOLYTIC AND THE RHEOLOGICAL PROPERTIES OF SOFT CAPRINE MILK CHEESE

Author
item Van Hekken, Diane
item Tunick, Michael
item PARK, YOUNG - FT.VALLEY STATE U., GA

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/28/2005
Publication Date: 7/20/2005
Citation: Van Hekken, D.L., Tunick, M.H., Park, Y.W. 2005. Effect of frozen storage on proteolytic and the rheological properties of soft caprine milk cheese. Journal of Dairy Science. 88:1966-1972.

Interpretive Summary: Soft cheese made from goat's milk is a high-valued dairy product with a very dedicated consumer base supporting the small but growing goat dairy industry in the U.S. Seasonal milking of the goats and the short shelf life of the soft cheese is a major problem in supplying this cheese year round. Freezing the fresh cheese curd maybe one way for U.S. manufacturers to store the cheese for equal distribution throughout the year. Because freezing is known to cause textural damage to some cheeses, this study was conducted to see if the same treatment would alter the texture of soft goat cheese. Unsalted plain soft cheeses were obtained from a goat dairy in Georgia and some were kept at refrigerated temperatures for one month as controls while the rest were frozen for 2 days, 3 months, and 6 months before being thawed and kept at refrigerated temperatures for one month. Soft goats' milk cheeses have fragile textures and the results showed that ice crystals formed in the cheese and had measurable impact on cheese texture. However, these changes are small and suggest that soft cheeses may be frozen to supply them throughout the year with minimal loss of texture quality.

Technical Abstract: The impact of freezing and long-term frozen storage on the proteolysis and rheology of soft cheese made from caprine milk was evaluated to determine the potential for extending its availability year round. Unsalted plain soft cheeses were obtained from a grade A goat dairy in Georgia and received 4 storage treatments: fresh control, C, aged at 4'C for 28 days; frozen control, FC, stored at -20'C for 2 days before being thawed; three months frozen, 3MF, stored at -20'C for 3 months before being thawed; and six months frozen, 6MF, stored at -20'C for 6 months before being thawed. All frozen cheeses were place in 4'C storage to thaw and then to age for 28 days. Proteolysis was determined using SDS-PAGE and rheological properties were measured at day 1, 14, and 28. At the start of refrigerated storage, all samples contained similar amounts of beta-CN and alphaS2-CN and over the 28 days of 4'C storage, showed slight (less than 4%) decrease in caseins with concomitant increase in peptide fragments. The C cheese had fragile textures and average means of 10.6 N for hardness, 10.1 mJ for chewiness, 0.12 for cohesiveness, 16.2 kPa for elastic modulus, 5.3 kPa for viscous modulus, and 1.7 kPa.s for complex viscosity. At day 1, the FC cheeses usually had significantly lower values for rheological properties, while 6MF tended to have the highest values. The creation and removal of ice crystals in the cheese matrix and the limited proteolysis of the caseins have small, but measurable, impact on cheese texture. However, these changes are small and suggest that soft cheeses may be supplied throughout the year with minimal loss of textural quality.