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 degrees C/min from 45 to -20 degrees 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 degrees C/min. XRDT evidenced that AGMF crystallizes under four different lamellar structures, two with double-chain length packings at 41.5 and 38.2 angstroms and two with triple-chain lengths of 72 and 64.7 angstroms stacking. Simultaneous wide-angle XRDT has shown that initial nucleation mainly occurs in a packing of beta' type from approximately 26 degrees C, although some transient presence of alpha was detected. The absence of polymorphic transition, on heating, until final melting (approximately 40 degrees C) demonstrated the relative stability of the structures formed.
Ben Amara-Dali
Wafa
W
Equipe Physico-Chimie des Systèmes Polyphasés, UMR 8612 du CNRS, 5 rue J. B. Clément, 92296 Châtenay-Malabry, France.
Karray
Nadia
N
Lesieur
Pierre
P
Ollivon
Michel
M
D000465:Algorithms; D000818:Animals; D002152:Calorimetry, Differential Scanning; D003460:Crystallization; D005223:Fats / Q000032:analysis*; D005990:Glycerol / Q000032:analysis; D006041:Goats / Q000378:metabolism*; D008892:Milk / Q000737:chemistry*; D013816:Thermodynamics
D005223:Fats; D005990:Glycerol