Abstract
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.
Highlights
Phytosterols are plant-based compounds with a chemical structure similar to cholesterol [1].In the last two decades, phytosterols have gained much scientific and commercial interest due to their cholesterol-lowering activity [2,3,4,5]
Phytosterols can be esterified with fatty acids to obtain phytosterol esters (PEs) to enhance their solubility in lipid-containing food products such as margarines and spreads [6]
The crystallization crystallization and melting curves of the β-sitosteryl esters are shown in Figure 1A,B, respectively, respectively, and and the the parameters parameters obtained obtained from from them them are are listed listed in in Table
Summary
Phytosterols are plant-based compounds with a chemical structure similar to cholesterol [1]. In the last two decades, phytosterols have gained much scientific and commercial interest due to their cholesterol-lowering activity [2,3,4,5]. Phytosterols can be esterified with fatty acids to obtain phytosterol esters (PEs) to enhance their solubility in lipid-containing food products such as margarines and spreads [6]. In this type of food products, the crystallization and melting behavior of lipids is of extreme importance because their macroscopic properties, such as spreadability, hardness, appearance and mouth feel strongly depend on it [7]. Fundamental research on the crystallization and melting behavior of PEs is very scarce.
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