聚乙烯醇-海藻酸钠-乳清蛋白复合膜结构及性质研究

Study on structure and properties of polyvinyl alcohol-sodium alginate-whey protein composite film

以聚乙烯醇(polyvinyl alcohol,PVA)、海藻酸钠(sodium alginate,SA)和乳清蛋白(whey protein,WP)为基质,以单宁酸(tannic acid,TA)为交联剂,采用溶液浇铸法制备了复合膜,研究了热处理和超声处理对不同PVA∶SA(质量比,12∶8和14∶6)复合膜的结构和理化性质的影响;利用复合膜基液对圣女果进行涂覆,评价了复合膜对其保鲜效果。结果表明,与PVA膜相比,随着SA、WP和TA的添加,复合膜基液黏度显著下降,膜的亮度降低,水接触角增大。热处理与超声处理均增大了复合膜的含水率,降低了复合膜的水蒸气透过率;其中PVA∶SA为12∶8的热处理组复合膜的水接触角最大,水蒸气透过率最低。与PVA膜相比,添加SA后,复合膜的拉伸强度和断裂伸长率显著提升,其中14∶6复合膜的拉伸强度和断裂伸长率最大。圣女果保鲜试验显示,复合膜包覆的圣女果贮藏30 d后色泽依然鲜艳,有效延长了保鲜期。研究结果可为果蔬保鲜涂覆膜材料的制备提供参考依据。

Polyvinyl alcohol(PVA),sodium alginate(SA),and whey protein(WP)were chosen as the matrix,and tannic acid(TA)as the crosslinking agent,to prepare the composite film using the solution casting method.The effects of heat treatment and ultrasound treatment on the structure and physicochemical properties of the composite films with different PVA∶SA mass ratios(12∶8 and 14∶6)were studied.The effect of the composite film on the freshness of cherry tomatoes during storage was evaluated.Results showed that with the addition of SA,WP,and TA,the viscosity of the mixture for composite film decreased significantly compared to PVA film,the brightness of the film decreased as well,but the water contact angle increased.The moisture content of the composite film increased under heat treatment or ultrasound treatment compared to un-pretreated composite film,whilst the reduction of the water vapor permeability was found after heat treated or ultrasound treated.The composite film with the PVA∶SA ratio of 12∶8 had the highest water contact angle and the lowest water vapor permeability among others.With the addition of SA,the tensile strength of the composite film and elongation increased,among which the film with the PVA∶SA ratio at 14∶6 had the highest tensile strength and elongation.The preservation experiment showed that the shelf life of the cherry tomato was prolonged with the coating of the composite film,which still kept fresh after 30 days of storage.The results could provide the basic references for the preparation of coating film materials for fruit and vegetable preservation.