L-精氨酸/L-赖氨酸改性大豆分离蛋白乳化性

L-Arginine (L-Arg)/L-lysine (L-Lys) ameliorate emulsifying properties of soy protein isolate

摘要:

在质量浓度为20 g/L大豆分离蛋白（SPI）中分别加入终质量浓度均为1、3 g/L的L-精氨酸（L-Arg）和L-赖氨酸（L-Lys），以不加氨基酸、仅调节与上述溶液对应相同pH的样品为处理对照，制备水包油型（O/W）乳状液。通过物化手段及光谱技术表征SPI结构、溶液的物化性质和乳化性能以及乳状液的微观结构。结果表明，L-Arg、L-Lys可提升SPI溶液的pH，显著提高蛋白溶解度（从77.1%到最大91.3%）、降低浊度，促进蛋白分子疏水性基团折叠而降低蛋白疏水性，有效降低SPI在溶液中的粒径大小并提高蛋白带电量，降低蛋白所成乳状液的乳滴大小且提高其均匀性；改性后的SPI比对照组的乳化性和乳化稳定性分别提高了31.4%和78.9%；相比之下，L-Arg比L-Lys更能有效地改性SPI结构而获得更高的乳化性，且乳化性随着这两种氨基酸浓度增加而增强。

Abstract:

L-Arginine (L-Arg) and lysine (L-Lys) with final concentrations at 1 g/L and 3 g/L were added to 20 g/L soy protein isolate (SPI) solution, respectively. The samples without the addition of L-Arg or L-Lys but with adjusting to the corresponding same pHs with of the added L-Ary or L-Lys were served as the control. These samples were then subjected to prepare oil-in-water (O/W) emulsions. The physical and chemical measurements and spectral scanning techniques were employed to detect the structure, physicochemical properties and emulsifying properties of SPI. Subsequently, the microstructure of the resulting emulsions was accordingly characterized. The results have shown that the addition of L-Arg and L-Lys increased the pHs of the SPI solutions and significantly improved the solubility (from 77.1% to max 91.3%), dramatically decreased the turbidity. Due to the protein folding of the hydrophobic group and resulting lowered protein hydrophobicity, L-Arg/L-Lys also effectively reduced the SPI particle size in the solution but also increased the charge, significantly reduced the size of emulsion droplets and promoted their uniformity. Consequently, the maximum 31.4% of the SPI emulsifying activity index and 78.9% emulsifying stability index of the L-Arg/L-Lys-treated samples were obtained. Comparatively, L-Arg was capable of modifying the SPI structure more effective than L-Lys to obtain enhanced emulsifying properties and the ameliorating effect was increased with the increasing concentrations of the two amino acids.