REVISED PROTOCOL FOR THE ANALYSIS OF MELTING PROPERTIES OF MOZZARELLA CHEESE BY HELICAL VISCOMETRY

A method that employs helical viscometry to evaluate the melting behavior of Mozzarella cheese was reported earlier. During analyses of numerous Mozzarella cheeses of varied age and composition, it was observed that some cheeses form a natural layer of free oil at the sample surface, but others do not. It was thought that free oil accumulation might cause variation in the measurement of apparent viscosity. Therefore, experiments were conducted to determine whether addition of exogenous butter oil could reduce analytical error by minimizing the differences in sample surface conditions. Effects of cheese age (2 or 21 d), cheese type (low moisture or low moisture part skim), and butter oil addition (0, 25, or 100 ml at 60-degrees-C) on sample temperature uniformity during analysis and apparent viscosity were evaluated. Added butter oil significantly reduced surface cooling and apparent viscosity in 2-d-old but not in 21-d-old cheeses. Surface cooling and desiccation in 21-d-old cheeses were minimized by the formation of natural free oil, which negated the effect of added butter oil. Adding exogenous butter oil effectively standardized the surface conditions of samples that oiled off to varying degrees, resulting in better analytical performance. Repeatability of the test with added butter oil (25 ml) was evaluated.