作 者：
胡坦;张珮珮;郑婷;黄行健;潘思轶;胡昊
关键词：
蛋白;热处理;工艺;高场强超声;冷凝胶;构象;微观结构;凝胶性
摘 要：
为探究高场强超声技术对大豆分离蛋白葡萄糖酸内酯冷凝胶性的影响,该研究将高场强超声技术与加热处理联用,对大豆蛋白进行预处理后形成冷凝胶。采用质构仪、圆二色谱、荧光色谱、扫描电镜、电泳、粒度仪等多种表征手段,比较了2种高场强超声-加热联用工艺对大豆分离蛋白冷凝胶凝胶性的影响,并推测其作用机理。研究发现:与传统加热预处理相比,2种高场强超声-加热联用预处理都能够显著(P<0.05)增强大豆分离蛋白冷凝胶的持水性和凝胶强度。工艺一(20 k Hz,400 W下先超声0、2、4、10 min后加热20 min)制备的冷凝胶的凝胶强度与持水性随超声时间的增加逐步增加(凝胶强度由(5.83±0.31)g增加到(46.37±1.15)g;持水性由42.04%±1.59%增加到81.74%±6.22%),而工艺二(先加热20 min后超声0、2、4、10 min)制备的冷凝胶的凝胶强度与持水性在较短超声时间内(4 min内)迅速增加(凝胶强度由(5.83±0.31)g增加到(37.57±2.57)g;持水性由42.03%±1.85%增加到79.31%±3.00%)。与工艺一相比,工艺二能够在较短超声时间内增强大豆分离蛋白冷凝胶性的机理可能在于:工艺二的处理方式,大豆蛋白经过热处理后充分展开、变性,使超声作用能在较短的时间内对大豆分离蛋白的二级结构和三级结构明显改变,暴露更多疏水基团,增加疏水环境和表面疏水性,增强蛋白在溶液中的溶解性,并增强大豆蛋白分子间的静电相互作用,从而形成致密、均一的微观凝胶结构,增加凝胶的持水性和凝胶强度。研究结果可为高场强超声-加热联用技术在大豆加工领域中的应用提供参考。
译 名：
High intensity ultrasound-heat pretreatments improving gelation properties of cold-set soy protein isolate induced by glucono-δ-lactone
作 者：
Hu Tan;Zhang Peipei;Zheng Ting;Huang Xingjian;Pan Siyi;Hu Hao;College of Food Science and Technology, Huazhong Agricultural University;
关键词：
proteins;;heat treatment;;processing;;high intensity ultrasound;;cold-set gels;;conformational structure;;microstructure;;gelation properties
摘 要：
In order to explore the effects of high intensity ultrasound(HIU) on the gelation properties of glucono-δ-lactone(GDL) induced cold-set soy protein isolate(SPI), this study used HIU-heat pre-treated SPI to form GDL induced cold-set SPI gels. Texture analyzer, circular dichroism(CD) spectrum, fluorescence chromatography, scanning electron microscope(SEM), sodium dodecyl sulphate-polyacrylamide gel electrophoresis(SDS-PAGE) and particle sizer were used in this study. Compared with heat pretreatment, HIU-heat pretreatments increased the gel strength and water holding capacity(WHC) of cold SPI gels significantly(P<0.05). HIU-heat pretreatment of SPI could not change the primary structure of SPI. However, the secondary structure, tertiary structure, intermolecular forces, protein solubility and particle size of SPI were changed after HIU-heat pretreatments. For instance, HIU-heat pretreatments increased the α-helix amount but decreased the β-sheet amount as demonstrated by far-CD spectra. Moreover, HIU-heat pretreatments of SPI increased the surface hydrophobicity, free or total sulfhydryl groups of SPI. The near-CD spectra and fluorescence spectra indicated that HIU-heat treatments reduced the tertiary structure and increased the hydrophobic environments of SPI. The protein solubility in different solvents(DW, deionized water at pH value of 8.0; Buffer B, Tris-glycine buffer(0.086 mol/L Tris, 0.09 mol/L glycine, and 4 mmol/L Na2 EDTA, pH value of 8.0); Buffer BSU, Buffer B containing 0.5% sodium dodecyl sulphate and 6 mol/L urea) suggested that HIU-heat treatments increased the electrostatic interactions but reduced or did not change non-covalent interactions among SPI molecules. SEM showed that the three-dimensional(3D) structure of HIU-heat pretreated SPI gels became denser and more uniform. However, different HIU-heat pretreatments influenced the gelation properties of SPI gels diversely. The gel strength and WHC of gels prepared by Method 1(M1, HIU for 2, 4 or 10 min then heating at 95 ℃ for 20 min) increased gradually with the increasing of HIU time(gel strength: from(5.83±0.31) to(46.37±1.15) g, WHC: from 42.03%±1.59% to 81.74%±6.22%), while those of gels prepared by Method 2(M2, heating at 95 ℃ for 20 min then HIU for 2, 4 or 10 min) increased rapidly within 4 min under HIU(gel strength: from(5.83±0.31) to(37.57±2.57) g, WHC: from 42.03%±1.85% to 79.31% ± 3.00%). This means that M2 can shorten the total producing time and reduce the energy, which might have more potential in soy bean protein industry. The mechanism for the above differences between M1 and M2 may be due to that the heating pretreatment could facilitate the unfolding of SPI, causing the following HIU treatments to modify SPI more easily. Therefore, M2 could change the conformational structures of SPI within a short time of HIU(within 4 min), resulting in the improvement of exposing hydrophobic groups, the increase of hydrophobic environment, the increase of surface hydrophobicity and the increase of protein solubility in DW, as demonstrated by CD, fluorescence and spectrophotometer data. Moreover, the intermolecular electronic interactions also increased as demonstrated by the protein solubility changes in DW, Buffer B and Buffer BSU. Therefore, a more uniform and denser micro-structure was formed to increase the gel strength and WHC as demonstrated by SEM. The results of this study can facilitate the application of HIU-heat technology in soy protein industry.
