水相大豆分离蛋白对油包水乳液稳定性的影响

Effect of Soybean Protein Isolates in Aqueous Phase on the Stability of Water-in-Oil Emulsions

以富含多不饱和脂肪酸的核桃油为油相,于水相添加大豆分离蛋白（SPI）,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 d测定乳液的平均粒径及粒径分布等物理特性,同时检测乳液初级及其次级氧化产物—脂质氢过氧化物与己醛,探究SPI对W/O乳液稳定性影响。结果表明,SPI应用于W/O乳液,乳液水滴粒径降低,乳液物理稳定性增大,SPI同时具有抗氧化活性。0.1%～0.4% SPI,蛋白质浓度的增大对乳液物理稳定性无显著性影响；SPI浓度增大（0.1%～0.2%）延长了脂质氢过氧化物与己醛形成延迟期,而浓度进一步增大（0.4%）乳液脂质氧化稳定性影响不显著。乳液水相pH对SPI抗氧化活性有显著影响,水相pH7.0,SPI抗氧化活性高于水相pH3.0。研究同时表明,水相钙离子强度0～200 mM CaCl2,钙离子引入提高了乳液物理稳定性；乳液水相钙离子强度较低时（≤10 mMCaCl2）,离子强度的增大降低了SPI抗氧化活性,较高离子强度（100～200 mM CaCl2）加速了乳液脂质氧化。

Walnut oil rich in PUEA was used as the oil phase and soybean protein isolates （SPI） were added into the water phase to prepare the water - in - oil （W/O） emulsions by using microfluidizer. The mean particle size and particle size distributions of emulsion were measured every other day, at the same time, the formation of primary oxidation products （lipid hydroperoxides） and secondary oxidation products （headspace hexanal） was determined to evaluate influence of aqueous phase SPI on the stability in W/O emulsions during storage at 45 ~C in the dark. The results showed that the application of SPI in W/O emulsions could decrease the partical size of emulsion drops, and improve the physical stability of W/O emulsions. With SPI at the levels of 0.1%-0.4%, the increasing of protein dose had non - significant effects on the physical stability of the emulsions ; The increasing of SPI dose at the levels of 0.1% -0.2% could prolong the delay period between lipid hydroperoxides and headspaee hexanal. However, the lip- id oxidative stability of the emulsions was not remarkably improved with the addition of 0.4% SPI. Aqueous phase pH had a significant effeet on the antioxidative stability of SPI. SPI had higher antioxidant activity at aqueous phase pH 7.0 than at pH 3.0. Meanwhile, the study indicated that calcium ion strength is 0-200 mmol/L CaCl2, whieh increased the physical stability of W/O emulsions. When levels of calcium ionie strength was low （≤10 mmol/L CaCl2 ）, the increasing of ionie strength suppresses the antioxidant aetivity of SPI, whereas its higher levels （ 100 200 mmol/L CaCl2 ） promoted lipid oxidation in the emulsions.