Stability Evaluation of pH-Adjusted Goat Milk for Developing Ricotta Cheese with a Mixture of Cow Cheese Whey and Goat Milk

Abstract

Excess summer milk and a lack of product diversity are major problems facing Taiwan's dairy goat industry. Gouda and Mozzarella cheeses made with cow milk are popular products for leisure farms in Taiwan, and they produce a large amount of cheese whey as waste. Our objective is to identify the unstable phenomena of pH-adjusted goat milk through the use of Turbiscan Lab^® Expert and to produce ricotta cheeses using cow cheese whey waste and excess goat milk. Delta backscattering (∆BS) profiles and the Turbiscan stability index (TSI) were used to evaluate the stability characteristics of goat milk adjusted to pH 6.7-5.2. The results show coagulation phenomena in skimmed goat milk and sedimentation phenomena in full-fat goat milk, when the pH was adjusted to 5.2. The TSI values of goat milk at pH 5.7 and 5.2 were significantly higher (<i>p</i> < 0.05) than that of a control. Therefore, 80/20 cow cheese whey/skimmed goat milk and 80/20 cow cheese whey/full-fat goat milk mixtures were acidified to pH 5.5 and heated at 90 °C for 30 min to produce ricotta cheeses A and B. The hardness value, moisture, protein, and ash contents of ricotta cheese A were significantly higher (<i>p</i> < 0.05) than that of ricotta cheese B, but no significant difference was found in terms of sensory evaluation.