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Comparative Study of Thermal and Structural Behavior of Four Industrial Lauric Fats

Anihouvi, Prudent Placide, Blecker, Christophe, Dombree, Anne, Danthine, Sabine
Food and bioprocess technology 2013 v.6 no.12 pp. 3381-3391
X-ray diffraction, cooling, differential scanning calorimetry, heat treatment, lipid content, melting, nuclear magnetic resonance spectroscopy, spatial distribution, stearic acid, temperature, tempering
The thermal and structural behavior of four industrial lauric fats, sold under the same commercial description, were investigated by using pulsed nuclear magnetic resonance (pNMR), differential scanning calorimetry (DSC), and X-ray diffraction (XRD) in order to obtain more basic information about their physical properties and particularly, about their polymorphism. The four fats have been classified into two groups based on their fatty acid (FA) and triacylglycerol (TAG) compositions: group 1 was characterized by its high concentration of stearic acid and group 2 by its high concentrations in lauric and myristic acids. After cooling and 24 h tempering at 4 °C, groups 1 and 2 crystallized in the β'2 and β'1 forms, respectively. These crystalline varieties corresponded to double-chain-length organizations (2 L) with the long spacing (LS) values around 36.48, 37.43, and 37.65 A for group 1, and 33.89, 34.00, 35.04, 37.64, and 37.76 A for group 2. During heating from 5 to 50 °C at 5 °C/min, the two groups evolved, respectively, from the 2Lβ'2 or 2Lβ'1 forms to liquid state without going through the 2Lβ form, indicating their great β' polymorph stability. However, after rapid cooling (-25 °C/min), all fats exhibited the same polymorphic evolution; they evolved from the α form between -30 and -10 °C to a mixture of α and β'2 forms with the vanishing of α crystal between 10 and 20 °C and that of β'2 polymorph at the temperatures above 35 °C. The passage to liquid state was also realized without the occurrence of β transition. The XRD data were in accordance with DSC melting profiles or with solid fat content (SFC) melting profiles. ©Springer Science+Business Media New York 2012.