Engineering the microstructure of milk fat by blending binary and ternary mixtures of its fractions

Abstract

In this study, the microstructure and crystallization kinetics of binary and ternary mixtures of milk fat fractions during isothermal crystallization at 5, 15, and 20 °C were characterized using polarized light microscopy and the Avrami model. Results showed that for both binary and ternary mixtures, high concentrations of the high-melting fraction result in the formation of rod or needle-like crystals (i.e., one-dimensional growth and low values of Avrami index, n) while at relatively higher concentrations of the middle-melting and low-melting fractions, multi-dimensional crystal growth is favored (i.e., higher n values). On the effect of temperature, for binary mixtures, it was found that at high undercooling conditions (5 °C) one dimensional growth is favored while for ternary mixtures, increasing the crystallization temperature (i.e., decreasing supersaturation) from 15 to 20 °C results in large differences in crystal structure. Mechanisms for the observed behavior are also suggested.