超声联合酶处理下TG酶交联大豆分离蛋白凝胶特性研究

Effect of Ultrasonic Combined with Enzyme Treatment on Glutamine Transaminase Cross-linked Soybean Protein Isolate Gels

为研究超声联合酶处理对大豆分离蛋白(SPI)结构和对谷氨酰胺转氨酶(TG)交联的SPI凝胶性能的影响,采用内源性荧光光谱、傅里叶红外变换光谱解析超声联合酶处理对SPI结构的影响,并以粒径、游离巯基含量、表面疏水性、凝胶强度、持水性及微观结构为指标,探究SPI结构改变与功能特性之间的关系。红外及荧光光谱表明,与未经处理SPI和经单一改性处理的SPI相比,超声联合酶处理使蛋白α-螺旋和β-转角相对含量降低,β-折叠和无规则卷曲相对含量上升,蛋白结构伸展,促使游离巯基和疏水基团暴露,提高了SPI游离巯基含量和表面疏水性。与未处理SPI相比,经超声联合酶处理的SPI凝胶效果最佳,形成了均匀致密的凝胶网络,其凝胶强度和持水率分别提升了(278.04±18.81)%和(89.51±2.78)%,超声联合酶处理可以改善SPI结构以及TG交联的SPI凝胶特性。

Aiming to study the effect of ultrasonic combined with enzyme treatment on the structure of soybean protein isolate(SPI)and the properties of SPI gel crossl-inked with glutamine transaminase(TG).The effects of ultrasonic combined with enzyme treatment on the structure of SPI were analyzed by fluorescence spectroscopy and Fourier transform infrared spectroscopy.Meanwhile,the relationship between SPI stuctural changes and functional characteristics were studied by particle size,free sulfhydryl group,surface hydrophobicity analysis,texture,water holding analysis and scanning electron microscopy.The results showed that after ultrasonic treatment,papain treatment and ultrasonic combined with enzyme treatment,the proportions of the secondary structure fractionsα-helix andβ-turn were decreased significantly(P<0.05),and the proportions ofβ-sheet and random coil were increased significantly(P<0.05),the protein structure was extended,the free sulfhydryl group and hydrophobic group were exposed,thus the free sulfhydryl group content and surface hydrophobicity of SPI were increased.Compared with untreated SPI,the SPI gel prepared by ultrasound combined with enzyme treatment formed a uniform and dense gel network,and its gel strength and water holding capacity(WHC)were significantly improved,which were increased by(278.04±18.81)%and(89.51±2.78)%,respectively.In addition,the gel strength and WHC were higher in the SPI gel treated with a combination of ultrasound and enzyme than that treated with ultrasound or enzyme alone,exhibiting the synergistic effect of enzymatic and ultrasonic treatment.In summary,ultrasound combined with enzyme treatment can improve the structure of SPI and the characteristics of TG cross-linked SPI gel.