Physicochemical and structural properties of compound dairy fat blends

The physicochemical properties of fat model systems made of commercial samples of anhydrous milk fat (AMF) or a fraction blended with palm oil (PO) were studied. Physical properties such as solid fat content, melting curves by differential scanning calorimetry, textural properties, and polymorphism were investigated. The objective of the present work was to systematically map interactions (compatibility/incompatibility) that occur in such model of compound fat systems with respect to butyric-based shortening or butter-like spreads formulations. For that purpose, iso-solid diagrams have been constructed from p-NMR data. Molecular interactions have been highlighted for all the blends, especially at low temperatures. Compositions at which molecular interactions were detected depend on the TAGs composition of the fractions involved in the blends. For example, under dynamic conditions, a minimum was observed (eutectic interaction) for all the blends. This minimum was shifted to higher PO content for blends made of AMF fractions with lower iodine value (IV) and to lower PO content for AMF with higher IV. After static crystallization followed by a tempering at 15°C, interactions also existed for all the blends. It was shown that the deviations found in hardness after this tempering procedure can be explained by intersolubility, polymorphic and microstructure arguments. PRACTICAL APPLICATIONS: Results reported here concern physical characteristics of several compound fat blends (butyric–vegetal). A comprehensive analysis of binary fat blends made of AMF, or its fractions, blended with a vegetal fat was conducted. This better understanding of crystallization phenomena occurring is required to further enhance the use of AMF in compound-margarines and shortenings. Indeed phase properties of fat blends have a significant influence on the sensorial characteristics of the final products (hardness, brittleness, grainy or smooth texture, …). This study is relevant for the dairy food industry as it may contribute to the development of new mixed-fat products, also sometimes called dairy blends.