Effects of aging on rheological and proteolytic properties of goat milk Jack Cheese produced according to cow milk procedures

Pasteurized milk from French Alpine goats was processed into Jack Cheese according to modified processing conditions used for manufacturing Monterey Cheese from bovine milk. The effect of time on proteolytic and rheological changes that occurred on this cheese during aging was investigated. Commercial mesophilic culture, Lactococcus lactis subsp. lactis, was added to milk at the rate of 16 ml/1001. The percentages of moisture, salt, protein, and fat in this cheese were 46.43, 1.19, 22.38, and 27.4, respectively. The salt to moisture ratio was 2.56. This cheese was vacuum-packed and stored at 4-5 degreesC for 30 weeks and the rheological and proteolytic properties were determined. The force required to compress the cheese to 20% of its original height during the first cycle increased during aging. However, the force required to compress the cheese to 75% of its original height during the first cycle did not change during aging. Similar trends were found during the second compression cycle. Elasticity values at 20% compression increased during aging; however, at 75% compression they did not change. Electrophoretic analysis of the caseins in the goat milk Jack Cheese revealed that beta casein was the most abundant casein and was less susceptible to proteolysis than other caseins. The alpha and kappa caseins were the second and the third major caseins in goat Jack Cheese, respectively. Similar to bovine gamma caseins, as beta casein was hydrolyzed in this cheese it gave rise to gamma caseins. The modified manufacturing conditions and elucidation of the chemical and physical properties of this goat milk cheese are not only providing scientific information for further research but also furnishing valuable information for practical application in production of goat milk Jack Cheese. (C) 2004 Elsevier B.V. All rights reserved.