植物单宁对酪蛋白膜的改性研究

目的 为研究不同单宁对酪蛋白膜的改性效果，探究水解类(塔拉单宁)和缩合类(杨梅单宁)单宁在不同添加量(酪蛋白固含量的5%、10%和15%)条件下对酪蛋白膜性能的影响。方法 使用溶液浇铸法制备单宁改性酪蛋白膜，对改性薄膜的水分含量、水溶性、水蒸气透过率、不透明度、紫外光屏蔽性、拉伸力学性能、热稳定性、形貌特征、抗氧化性能及化学结构进行表征。结果 塔拉单宁的添加量与改性酪蛋白膜的水分含量和水溶性呈正相关，杨梅单宁的添加量与改性酪蛋白膜的含水率和水溶性呈负相关;单宁改性后的酪蛋白膜不透明度值上升，2种单宁均能降低酪蛋白膜的水蒸气透过率和紫外光透过率，减缓酪蛋白膜的质量损失速率，增强薄膜抗氧化性;杨梅单宁有效提升了酪蛋白膜的拉伸力学性能、热稳定性及一定的抗氧化性，杨梅单宁添加量为15%时，改性酪蛋白膜性能最佳。结论 2种单宁都能赋予酪蛋白膜更优异的紫外光屏蔽性、水蒸气阻隔性和抗氧化性，杨梅单宁对酪蛋白的交联改性效果优于塔拉单宁，可有效提高酪蛋白的拉伸力学强度和热稳定性。单宁改性后的酪蛋白膜在活性包装领域上具有一定的应用潜力。

Modification of Casein-based Membrane with Plant Tannins

The work aims to study the modification effects of different tannins on casein-based membranes and evaluate the effects of hydrolysable (Tara tannin) and condensed (Chinese bayberry) tannins of different contents (5%, 10% and 15%) on the properties of casein-based membranes. The casein-based membranes modified by tannins were prepared by the solution casting method. The moisture content, water solubility, water vapor permeability (WVP), opacity, ultraviolet (UV) shielding capacity, tensile property, thermal stability, morphology, antioxidant capacity and chemical structure of the modified membranes were characterized. A positive correlation between tannin content and moisture content as well as water solubility was found in membranes introduced with tara tannins, however, the opposite result was observed in those membranes incorporated with Chinese bayberry tannins. The opacity of casein-based membranes modified with tannins increased. The introduction of two tannins in casein-based membranes provided lower WVP and UV transmittance, decreased the weight loss rate and increased antioxidant capacity of resulting membranes compared with native casein-based membrane. Chinese bayberry tannins effectively contributed to good tensile strength, thermal stability and antioxidant properties of casein-based membranes. Especially when the content of tannin increased to 15 wt.%, modified casein-based membranes had the best properties. Both the two plant tannins can provide casein-based membranes better UV shielding capacity, WVP and antioxidant capacity. Chinese bayberry tannin presented better cross-linking modification capacity in casein-based membranes compared with Tara tannin, yielding a better tensile strength and thermal stability of the resulting membranes. Tannin-modified casein-based membranes have application potential in active food packaging.