Anhydrous Goat's Milk Fat: Thermal and Structural Behavior. 1. Crystalline Forms Obtained by Slow Cooling

The thermal and structural behaviors of anhydrous goat's milk fat (AGMF) have been determined as a function of temperature using a powerful technique allowing simultaneous time-resolved synchrotron X-ray diffraction as a function of temperature (XRDT) and high-sensivity differential scanning calorimetry (DSC) measurements from the same sample. This first paper, aiming at the characterization of the physical properties of AGMF, we examine crystalline organizations made by triacylglycerols (TG) upon slow cooling at |dT/dt| = 0.1 °C/min from 45 to −20 °C in order to approach system equilibrium. Three overlapped exotherms were observed by DSC upon cooling, whereas four endotherms were found on the subsequent heating at 1 °C/min. XRDT evidenced that AGMF crystallizes under four different lamellar structures, two with double-chain length packings at 41.5 and 38.2 Å and two with triple-chain lengths of 72 and 64.7 Å stacking. Simultaneous wide-angle XRDT has shown that initial nucleation mainly occurs in a packing of β‘ type from ∼26 °C, although some transient presence of α was detected. The absence of polymorphic transition, on heating, until final melting (∼40 °C) demonstrated the relative stability of the structures formed. Keywords: Goat's milk fat; polymorphism; X-ray diffraction; differential scanning calorimetry, TG composition