Compositional effects on milk fat crystallization.

Seasonal and regional variability in milk fat composition causes differences in crystallization behavior, which can, for example, result in variability in fractionation efficiency and physical properties of butter. However, the specific compositional causes of variability in milk fat crystallization behavior are still only poorly understood. In this work, the seasonal and regional variations in composition of anhydrous milk fat were analyzed and related to crystallization behavior. Although there were no clear-cut trends in chemical composition (triacylglycerol, fatty acid, and minor lipid profiles) among the milk fats, significant differences in crystallization behavior were observed. For anhydrous milk fat samples made from sweet cream and obtained from the same milk supply through a period of 14 mo, no significant trends in either composition or crystallization behavior were observed. This suggests that seasonal variability of milk fat may be reduced by current feeding strategies in the United States. More detailed examination of the triacylglycerol profiles led to the conclusion that the relative contents of certain triacylglycerol combinations correlated well with crystallization behavior. In particular, the ratio of higher-melting to lower-melting triacylglycerols could be used to predict crystallization behavior. Higher ratios of higher-melting triacylglycerols led to higher crystallization rate.