桃仁分离蛋白质对油包水乳液物理与氧化稳定性的影响

以富含多不饱和脂肪酸的核桃油为油相，于水相添加桃仁分离蛋白（PKPI），采用超高压微射流均质机制备油包水（W/O）乳液，乳液于45 ℃避光保存，每隔1 day测定乳液的平均粒径及粒径分布等物理特性，同时检测乳液初级氧化产物—脂质氢过氧化物与次级氧化产物-己醛，探究PKPI对W/O乳液稳定性影响。结果表明，PKPI应用于W/O乳液，可以降低乳液油滴粒径，提升乳液物理稳定性，PKPI同时具有抗氧化活性；PKPI浓度0.1~0.4%，乳液物理及氧化稳定性随PKPI浓度的增大而增强。水相pH对PKPI抗氧化活性有显著影响，水相pH 7.0，PKPI抗氧化活性高于水相pH 3.0。水相钙离子强度同时影响PKPI乳液的稳定性，100~200 CaCl2 mM，乳液物理稳定性随离子强度的增大而增强；乳液水相钙离子强度较低时（≤10 mM），增大离子强度将降低PKPI抗氧化活性，钙离子强度较高时（≥100 mM）,增大离子强度加速乳液脂质氧化。
A water-in-oil (W/O) emulsion was prepared using a microfluidizer, with walnut oil rich in polyunsaturated fatty acids as the oil phase. Peach kernel protein isolates (PKPIs) were added to the aqueous phase, and the emulsion was stored in the dark at 45?C. The particle size distribution, mean particle size, and other physical properties were measured on alternate days, and the primary oxidation products (lipid hydroperoxides) and secondary oxidation product (headspace hexanal) were determined in order to evaluate the influence of aqueous phase PKPI on the stability of W/O emulsions. The results showed that the application of PKPIs could reduce the emulsion droplet size and improve the physical stability of W/O emulsions. Additionally, PKPIs show antioxidant activity; at the concentration range of 0.1~0.4 wt%, the physical and oxidative stability of W/O emulsions increases with the increasing PKPI concentrations. Aqueous phase pH had a significant effect on the oxidative stability of emulsions. The antioxidant activity of PKPI at aqueous phase pH 7.0 was higher than that at pH 3.0. Calcium ionic strength of aqueous phase also had an important impact on the stability of PKPI W/O emulsions. When the concentration of CaCl2 was in the range of 100-200 mM, the physical stability of the emulsions increased with increasing ionic strength. At low levels of calcium ionic strength of aqueous phase in the emulsion (≤10 mM CaCl2), a high ionic strength was able to suppress the antioxidant activity of PKPI. At a high level of calcium ionic strength (≥ 100 mM CaCl2), a high ionic strength was able to accelerate lipid oxidation in the emulsions.