氧化对大豆蛋白结构、乳液稳定性及消化特性的影响

Influence of Oxidation on Soy Protein Structure, Emulsion Stability and Lipid Digestion

以大豆分离蛋白为原料,以脂质过氧化产物丙二醛(malondialdehyde,MDA)为氧化引发剂,逐级研究氧化对大豆蛋白结构、乳液稳定性及乳液消化特性的影响。结果发现:随着MDA浓度的升高,蛋白羰基及席夫碱含量明显升高而巯基含量显著降低。同时,MDA可促进蛋白聚集并诱导β-伴大豆球蛋白(7S)组分形成二硫键和非二硫键诱导的共价交联。进一步制备O/W型乳液,发现不同浓度MDA处理蛋白对乳液的形成影响较小,但可以显著改变界面蛋白组成。其中经中高浓度(2.5~10 mmol/L)MDA氧化后,更多7S组分以聚集状态参与界面组成。体外模拟胃肠道消化实验进一步表明,乳液消化主要在肠道进行,氧化诱导的蛋白交联/聚集可延缓或降低胆盐在界面的替代,进而减缓乳液消化并降低脂质释放率。

In this study, malondialdehyde(MDA), a natural lipid peroxidation product, was used as an initiator to investigate the influence of MDA-induced protein structural modifications on stability and digestibility of emulsion stabilized by soy protein isolate(SPI). Results obtained showed that the contents of protein carbonyl and Schiff base significantly increased along with increasing MDA concentration, accompanied by a noticeable decrease in protein sulfhydryl content. Meanwhile,MDA promoted protein aggregation through disulfide/non-disulfide covalent bonding, where β-conglycinin(7S) was mainly involved in the latter case. O/W emulsion was further prepared with oxidatively treated SPI. It was found that MDA-induced protein oxidation had less influence on emulsion formation, but they could significantly alter the protein composition of the interface. Herein, for SPI treated with MDA at concentrations of 2.5-10 mmol/L, more 7S fractions participated in interface formation in an aggregate state. Furthermore, results from in vitro simulated gastrointestinal digestion demonstrated that emulsion digestion occurred mainly in the intestinal tract, and oxidation-induced cross-linking/aggregation of proteins could delay or reduce the replacement of bile salts at the interface, which in turn slowed emulsion digestion and decreased lipid digestibility.