Chen Dongxia, Liu Yuheng, Li Jia, Sun Xiaozhen, Gu Jiadong, He Yang, Ci Hui, Wen Liankui, Yu Hansong, Xu Xiuying
College of Food Science and Engineering, Jilin Agricultural University, Changchun 130118, China.
Food Inspection Department, National Ratafia and Fruits and Vegetables Drinks Quality Surveillance Test Center, Tonghua 134000, China.
Foods. 2022 Mar 22;11(7):895. doi: 10.3390/foods11070895.
Anthocyanins are abundant in purple corn and beneficial to human health. Soybean protein isolate-7s (SPI-7s) could enhance the stability of anthocyanins. The stable system of soybean protein isolate-7s and delphinidin-3--glucoside complex (SPI-7s-D3G) was optimized using the Box-Behnken design at pH 2.8 and pH 6.8. Under the condition of pH 2.8, SPI-7s effectively improved the sunlight-thermal stabilities of delphinidin-3--glucoside (D3G). The thermal degradation of D3G conformed to the first order kinetics within 100 min, the negative enthalpy value and positive entropy value indicated that interaction was caused by electrostatic interaction, and the negative Gibbs free energy value reflected a spontaneous interaction between SPI-7s and D3G. The interaction of SPI-7s-D3G was evaluated by ultraviolet visible spectroscopy, circular dichroism spectroscopy and fluorescence spectroscopy. The results showed that the maximum absorption peak was redshifted with increasing the -helix content and decreasing the -sheet contents, and D3G quenched the intrinsic fluorescence of SPI-7s by static quenching. There was one binding site in the SPI-7s and D3G stable system. The secondary structure of SPI-7s had changed and the complex was more stable. The stabilized SPI-7s-D3G will have broad application prospects in functional foods.
花青素在紫玉米中含量丰富，对人体健康有益。大豆分离蛋白7S（SPI-7S）可以增强花青素的稳定性。采用Box-Behnken设计在pH 2.8和pH 6.8条件下优化了大豆分离蛋白7S与飞燕草素-3-O-葡萄糖苷复合物（SPI-7S-D3G）的稳定体系。在pH 2.8条件下，SPI-7S有效提高了飞燕草素-3-O-葡萄糖苷（D3G）的光热稳定性。D3G的热降解在100分钟内符合一级动力学，负的焓值和正的熵值表明相互作用是由静电相互作用引起的，负的吉布斯自由能值反映了SPI-7S与D3G之间的自发相互作用。通过紫外可见光谱、圆二色光谱和荧光光谱对SPI-7S-D3G的相互作用进行了评价。结果表明，最大吸收峰随着α-螺旋含量的增加和β-折叠含量的减少而发生红移，D3G通过静态猝灭猝灭了SPI-7S的内源荧光。SPI-7S与D3G稳定体系中有一个结合位点。SPI-7S的二级结构发生了变化，复合物更稳定。稳定化的SPI-7S-D3G在功能性食品中将具有广阔的应用前景。
