Crystallization and Rheological Properties of Milk Fat

Abstract

Milk fat is semi-solid in nature due to the presence of a large proportion of high melting triacylglycerols (TAGs). These TAGs form crystalline structures at room temperature, resulting in a network that confines the lower melting TAGs (in liquid state) within. Milk fat contains many different TAG species, each with its own melting temperature, resulting ina wide range of plasticity where both solid and liquid fats are present. The principal determinant of the consistency of semi-solid fats is the ratio of solid to liquid fat at a given temperature. Also important are the microstructure of the milk fat crystals and the spatial distribution of the solids within the network. These variables can be used to describe the rheological behaviour of milk fat and the differences that occur when samples have different compositions, are tested at different temperatures, or after modifying processing parameters, such as cooling rate or the application of shear. More variables must also be accounted for when discussing milk fat contained within food matrices, including ice cream, cheeses and baked goods. Overall, studying the relationships between milk fat composition, crystallization, structure, rheology and texture allows for a greater understanding of milk fat and containing products.