Vaikousi Hariklia, Lazaridou Athina, Biliaderis Costas G, Zawistowski Jerzy
Laboratory of Food Chemistry and Biochemistry, Department of Food Science and Technology, School of Agriculture, Aristotle University, Thessaloniki, Greece.
J Agric Food Chem. 2007 Mar 7;55(5):1790-8. doi: 10.1021/jf0624289. Epub 2007 Feb 13.
The thermal properties, solubility characteristics, and crystallization kinetics of four commercial phytosterol preparations (soy and wood sterols and stanols) and their blends with corn oil were examined. Differential scanning calorimetry (DSC) revealed narrow melting peaks between 138 and 145 degrees C for all phytosterol samples, reversible on rescan. Broader and less symmetrical melting transitions at lower temperatures with increasing oil content were observed for two samples of phytosterol-oil admixtures. The estimated, from the solubility law, deltaH values (34.7 and 70.7 mJ/mg for wood sterols and stanols, respectively), were similar to the DSC experimental data. Fatty acid esters of soy stanols differing in the chain length of the acyl groups (C2-C12) exhibited suppression of the melting point and increase of the fusion enthalpy with increasing chain length of the acyl group; the propionate ester exhibited the highest melting point (Tm: 151 degrees C) among all stanol-fatty acid esters. Solubility of phytosterols in corn oil was low (2-3% w/w at 25 degrees C) and increased slightly with a temperature rise. Plant sterols appeared more soluble than stanols with higher critical concentrations at saturation. The induction time for recrystallization of sterol-oil liquid blends, as determined by spectrophotometry, depended on the supersaturation ratio. The calculated interfacial free energies between crystalline sediments and oil were smaller for sterol samples (3.80 and 3.85 mJ/m2) than stanol mixtures (5.95 and 6.07 mJ/m2), in accord with the higher solubility of the sterol crystals in corn oil. The XRD patterns and light microscopy revealed some differences in the characteristics among the native and recrystallized in oil phytosterol preparations.
研究了四种商业植物甾醇制剂（大豆甾醇、木质甾醇和甾烷醇）及其与玉米油混合物的热性质、溶解性特征和结晶动力学。差示扫描量热法（DSC）显示，所有植物甾醇样品在138至145摄氏度之间有狭窄的熔点峰，重新扫描时具有可逆性。对于两个植物甾醇 - 油混合物样品，随着油含量增加，在较低温度下观察到更宽且对称性更低的熔融转变。根据溶解度定律估算的ΔH值（木质甾醇和甾烷醇分别为34.7和70.7 mJ/mg）与DSC实验数据相似。酰基链长度（C2 - C12）不同的大豆甾烷醇脂肪酸酯随着酰基链长度增加表现出熔点降低和熔融焓增加；丙酸酯在所有甾烷醇 - 脂肪酸酯中熔点最高（Tm：151摄氏度）。植物甾醇在玉米油中的溶解度较低（25摄氏度时为2 - 3% w/w），并随温度升高略有增加。植物甾醇在饱和时的临界浓度高于甾烷醇，似乎更易溶解。通过分光光度法测定，甾醇 - 油液体混合物重结晶的诱导时间取决于过饱和度比。甾醇样品（3.80和3.85 mJ/m²）结晶沉积物与油之间计算得到的界面自由能比甾烷醇混合物（5.95和6.07 mJ/m²）小，这与甾醇晶体在玉米油中的较高溶解度一致。X射线衍射图谱和光学显微镜显示，天然的和在油中重结晶的植物甾醇制剂在特征上存在一些差异。
