Fractionnement de la matière grasse laitière par cristallisation simple et son utilisation dans la fabrication de beurres mous

Abstract

Anhydrous milk fat was fractionated into 7 fractions by melt crystallization at temperatures ranging from 26°C to 9°C. The fractions were characterized by fatty acid and triglyceride composition, melting point profile and solid fat index. The process was based on a slow cooling of the melted fat, a short duration of stabilization at the fractionation temperature and the separation of the crystals from liquid phase by vaccum filtration. The liquid fractions were rich in smaller triglycerides as well as short chain and unsaturated fatty acids, whereas the solid fractions had high concentrations of larger triglycerides with long chain saturated fatty acids. The separation of milk fat triglycerides by molecular size is not feasible by melt crystallization as evidenced by the weight average molecular weight of various fractions ranging from 714,8 to 769,7 compared to 727,5 for native milk fat and the geometric mean-carbon number of fractions ranging from 38,4 to 44,9 compared to 41,0 for milk fat. Selected fractions were used for the preparation of spreadable butters which were characterized for their spreadability, melting temperature profile and dilatation. Experimental butters showed a 2 to 4 fold improvement in spreadability at 7°C compared to the regular butter and they approached the spreadability of soft margarine at 15°C. Butter made from a blend of 80% of liquid fraction obtained at 9°C and 20% of solid fraction, obtained at 26°C, was the most spreadable. The limitation in improving spreadability of butter from milk fat triglycerides alone, is discussed.