Comparison of Flavor and Some Chemical Properties of Instantized and Noninstantized Nonfat Dry Milk

This experimental work was planned to study changes in flavor, color, thiobarbituric acid, and acid ferricyanide optical density values on paired samples of instant and noninstant nonfat dry milks under various storage conditions. Hedonic scores for instant and noninstant milks were initially 5.6 and 5.7, respectively, and were 4.7 and 4.8 after storage at 120°F. Triangular taste tests results of the paired samples indicated no significant difference between most of the pairs, either before or after storage at both temperatures. Reflectance values at 520mµ and 400mµ wave lengths changed very slightly during storage and were approximately the same for both milks. The average thiobarbituric acid optical density values for the instant nonfat samples were 0.210 before, and 0.244 after storage at 100°F. The corresponding values for the noninstant nonfat samples were 0.103 before, and 0.161 after storage at 100°F. The average acid ferricyanide optical density values were similar to those obtained with the thiobarbituric acid method. It was concluded that the instantizing process did not adversely affect the flavor of nonfat dry milk, and that the thiobarbituric acid or acid ferricyanide tests for reducing compounds can not be used as an index of flavor quality of nonfat dry milk.