不同羟基结构的黄酮对鱼鳞明胶可食性膜的改性作用

通过分别添加木犀草素、槲皮素、杨梅素优化鱼鳞明胶可食膜，对比复合膜的机械性能和光学属性，探究不同羟基（—OH）数的黄酮与明胶分子的内部相互作用对鱼鳞明胶膜性能的优化作用。差示扫描量热仪和傅里叶变换红外光谱测定结果表明：植物黄酮在鱼鳞明胶膜中可能会形成明胶分子之间的空间阻隔作用；同时黄酮分子的—OH能与明胶分子形成氢键和偶极作用力，且作用力随着黄酮分子的—OH数目的增加而加强。黄酮分子的疏水环和—OH与明胶分子的作用力，导致鱼鳞明胶分子二级结构中的β-转角逐渐转化为β-折叠、无规则卷曲和α-螺旋；—OH数目的增加加强了明胶与黄酮的氢键、电荷间的偶极作用力，降低明胶分子链的移动性，致使黄酮膜内部结构更加致密，提升了明胶膜的拉伸延展性；黄酮的添加会增进明胶膜的紫外光吸收，但黄酮分子中—OH数目对膜的透光度无影响。本研究结果可为采用天然黄酮类物质优化明胶可食性包装膜提供理论指导。

Modification of Fish Scale Gelatin Edible Films Using Flavonoids with Different Hydroxyl Structures

Luteolin, quercetin and myricetin are natural plant flavonoids with similar structure and different numbers of hydroxyl groups. In this work, the mechanical and optical properties of fish scale gelatin edible films incorporated with luteolin, quercetin or myricetin were measured and compared with the aim of exploring the role of interaction between gelatin and flavonoids with different numbers of hydroxyl groups inside the composite films in improving the properties of the films. Differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy showed that steric hindrance between gelatin molecules was formed by the addition of the flavonoids. In the meantime, hydrogen bonds and dipole-dipole force were formed between the hydroxyl groups of flavonoids and gelatin, and they were strengthened with the increasing number of hydroxyl groups. The interactions between the hydrophobic rings and hydroxyl groups of flavonoids and gelatin molecules led to the secondary structural transition from β-turn to β-sheet, random coil and α-helix. As a result of the strengthened hydrogen bonds and dipole-dipole force between flavonoids and gelatin molecules with the increasing number of hydroxyl groups, the molecular mobility of gelatin was weakened, making the film structure more compact and elevating the tensile extensibility. Although incorporation of flavonoids improved the ultraviolet absorbance, the number of hydroxyl groups did not affect the light transmittance of gelatin films. These results can provide a theoretical guideline for the improvement of gelatin edible films with the addition of flavonoids.