Structural Study on Polymorphism of Cis-Unsaturated Triacylglycerol:  Triolein

Abstract

To clarify the influence of cis-unsaturation on solid-state structures of triacylglycerols (TAGs), the crystal structures of three crystalline phases (alpha, beta' and beta) of triolein [C3H5(OCOC17H33)3] were investigated by powder X-ray diffractometry and IR and Raman spectroscopy. The influence on the structural change of the alpha phase in the course of cooling was also studied. With respect to the subcell structure and conformational order of hydrocarbon chains in the beta and beta' phases, triolein resembles saturated TAGs; trans-zigzag hydrocarbon chains are adopted in the T(parallel) subcell for the beta phase and in the O(perpendicular) subcell for the beta' phase. The influence of cis-unsaturation was most obvious in the structure of the alpha phase and its temperature dependence. The alpha phase of triolein does not form the ordinary hexagonal subcell but a rather loose distorted subcell, which hardly changes in cooling, forming a striking contrast to the hexagonal-->pseudohexagonal subcell transformation found in the alpha phase of saturated TAGs.

Effect of unsaturated acyl chains on structural transformations in triacylglycerols

“…3b). The WAXS pattern of the b'-phase shows exactly the same features as those reported previously [6,7]. It has to be noted that, apart from the two peak maximums assigned to O ' usually associated with b'-phases (Fig.…”

“…This is the result of the packing density of the oleoyl hydrocarbon chains being direction dependent [6]. The WAXS pattern could be refined to suggest an orthorhombic unit cell (a so-called pseudo-hexagonal subcell) with two broad peaks corresponding to the 110 (d = 4.32 Å) and 200 (d = 4.01 Å) planes [6]. After isothermal crystallization at 223 K, increasing the temperature initiates the transformation of the a 1 -phase into the b'-phase (Fig.…”

“…There are four mostly common polymorphs in TAG phase transformations (sub-a-phase, aphase, b'-phase and b-phase). These phases have been identified in tristearin (StStSt) [4,5] or triolein (OOO) [6,7]. The a-phase of TAG -classified as a rotator phase (Fig.…”

Effects of Temperature and Humidity History on Brittleness of α-Sulfonated Fatty Acid Methyl Ester Salt Crystals

“…It is known that temperature history has an influence on fat crystalline structures. Akita et al reported that triacylglycerol, for example, had approximately three crystal polymorphs 26 , and these crystal polymorphs were transformed rapidly by thermal treatment around the phase transition temperature owing to melt-mediated crystallization 27 . In this study, sample B was prepared by using a process that included thermal treatment near the phase transition temperature, suggesting transformation of crystalline structures for sample B.…”

Synthesis, calorimetric studies, and crystal structures of N, O-diacylethanolamines with matched chains

“…, whereas C Ϫ O stretching from the ester moiety is observed around 1188-1178 cm ), which is characteristic of O ┴ chain packing (25)(26)(27). Even though the splitting of these bands is not clearly seen for didecanoylethanolamine, di- …”