Evidence of two β’ phases in tristearin

Abstract

Data from Raman spectroscopy, X‐ray diffraction analysis, differential scanning calorimetry and features of the preparative method are all consistent with the existence of 2 intermediate β’ phases for tristearin; the first, a lower melting phase, β’2, transforms at 61 C into the second, β’1 , which in turn changes at 64 C into β‐tristearin. Raman spectral evidence indicates that the 2 mesophases occur in an orthorhombic packing environment and that the β’2 to β’1 transition results from a change in lateral packing of the hydrocarbon chains.

A critical evaluation of Raman spectroscopy for the analysis of lipids: Fatty acid methyl esters

“…6), although approximately linear, had least squares regression coefficients of only 0.94 and 0.95 for the full range, which is very poor for a model system expected to be linear. However, there is evidence for odd/even alternation in the 1440/ν(C=O) plot in the region of the plot corresponding to medium (14)(15)(16)(17)(18)(19)(20) chain length, with the oddnumbered chains sitting above the best fit trend line and the even-numbered chains below it. Separating this plot into oddand even-numbered chains improves the regression coefficients to 0.98.…”

“…However, in solid TG, rotation is restricted so that in β ′ crystals, for example, one FA chain adopts the eclipsed conformation in order to pack efficiently and this gives rise to a second peak ca. 10 cm −1 below the usual position (18). In these cases, the heights of both bands will need to be combined for use as a molar standard.…”

“…In practice, the need to split the data for odd-and even-numbered chain lengths is unlikely to cause significant errors in Raman-based chain length calculations for natural fats and oils, since these are principally composed of TG with mediumlength (14)(15)(16)(17)(18)(19)(20), even-numbered chains. However, for some natural and processed fats and oils, such as lamb and beef fats, it may be necessary to establish calibrations allowing for significant amounts of odd-chain FA.…”

Characterization of the three major polymorphic forms and liquid state of tristearin by Raman spectroscopy

“…Two major vibrational spectroscopy-based techniques have been used to distinguish the molecular structure of TG polymorphs, namely infrared spectroscopy (Kobayashi et al, 1986;Kodali et al, 1989;Yano and Sato, 1999;Dohi et al, 2002;Chang et al, 2005;Yang et al, 2005) and Raman spectroscopy (Koyama and Ikeda, 1980;Simpson and Hagemann, 1982;Simpson, 1983;Hernqvist, 1984;Kobayashi et al, 1986;Kodali et al, 1989;Sprunt et al, 2000;Dohi et al, 2002;Yang et al, 2005;Meng et al, 2005; Bresson et al, 2005Bresson et al, , 2006Da Silva and Rousseau, 2008). These techniques can also provide substantial structural and thermodynamic information (Da Silva and Rousseau, 2008).…”

“…Tristearin was chosen as a model TG as it has been well-characterized with XRD and DSC (Larsson, 1966;Lutton, 1972;Simpson and Hagemann, 1982;Aronhime et al, 1987;Hagemann, 1988;Elisabettini et al, 1996;Oh et al, 2002;MacNaughtan et al, 2006) and its polymorphs are easy to prepare.…”