Research Unit Food and Lipids, Department of Microbial and Molecular Systems (M²S), KU Leuven, Campus Kulak Kortrijk, Etienne Sabbelaan 53 Box 7659, 8500 Kortrijk, Belgium.
Leuven Food Science and Nutrition Research Centre (LFoRCe), Kasteelpark Arenberg 20 Box 2463, 3001 Leuven, Belgium.
Molecules. 2020 Dec 4;25(23):5727. doi: 10.3390/molecules25235727.
This study investigated how the physicochemical characteristics of phytosterol esters are influenced by the chain length and degree of unsaturation of the fatty acid ester moiety. Saturated and unsaturated phytosterol esters (PEs) were synthesized by the esterification of different types of fatty acids (stearic, palmitic, lauric, oleic, and linoleic acid) to β-sitosterol. The non-isothermal crystallization and melting behavior of the pure PEs were analyzed. It was proven by X-ray diffraction that saturated β-sitosteryl esters and β-sitosteryl oleate formed a bilayer crystal structure. The lamellar spacings of the bilayer structure decreased with decreasing fatty acid chain length and with an increasing degree in unsaturation. The degree of unsaturation of the fatty acid chain of the β-sitosteryl esters also influenced the type of subcell packing of the fatty acid moieties in the bilayer structure, whether or not a metastable or stable liquid crystalline phase was formed during cooling. Furthermore, it was found that the melting temperature and enthalpy of the β-sitosteryl esters increased with an increasing fatty acid chain length while they decreased with an increasing degree of unsaturation. The microscopic analyses demonstrated that β-sitosteryl oleate formed much smaller spherulites than their saturated β-sitosteryl analogues.
本研究考察了植物甾醇酯的物理化学特性如何受脂肪酸酯部分的链长和不饱和度的影响。通过不同类型的脂肪酸（硬脂酸、棕榈酸、月桂酸、油酸和亚油酸）与 β-谷甾醇酯化合成了饱和和不饱和植物甾醇酯（PE）。分析了纯 PEs 的非等温结晶和熔融行为。X 射线衍射证明，饱和 β-谷甾醇酯和 β-谷甾醇油酸酯形成了双层晶体结构。双层结构的层间距随着脂肪酸链长的缩短和不饱和度的增加而减小。β-谷甾醇酯中脂肪酸链的不饱和度也影响双层结构中脂肪酸部分的亚细胞堆积类型，在冷却过程中是否形成亚稳或稳定的液晶相。此外，还发现 β-谷甾醇酯的熔融温度和焓随着脂肪酸链长的增加而增加，而随着不饱和度的增加而降低。微观分析表明，β-谷甾醇油酸酯形成的球晶比其饱和的 β-谷甾醇类似物小得多。
