茶多酚-壳聚糖复合膜的制备及保鲜效果研究

本研究以聚乙烯醇（PVA）和壳聚糖（CTS）为基材,甘油作为增塑剂,以茶多酚（TP）为功能性添加剂制备无污染、可降解且具有抗氧化功能的活性包装材料TP-CTS/PVA复合膜,分析TP浓度对复合膜机械性能、抗氧化能力、抑菌能力等理化性质的影响,研究复合膜与包装相关性能的影响,以期提高复合膜的综合性能。将其应用于圣女果的保鲜,测定其在贮存期间理化指标及微生物指标,进一步将不同TP浓度的复合膜涂抹于新鲜圣女果表面,分析圣女果在贮存期间的感官品质、腐烂率、失重率、可溶性糖、可滴定酸等指标的变化,系统研究复合膜对圣女果的保鲜效果。结果表明：以TP为功能性添加剂共混CTS和PVA制备的复合膜兼具抗氧化和抑菌效果;随着TP浓度增加,复合膜的颜色逐渐变深,TP浓度为1.5%时,复合膜的水溶性最低(19.85±0.64)%,此时复合膜的抗张强度呈最大值(13.19±0.77)MPa;当TP浓度增大,其对Escherichia coli和Staphylococcus aureus的抑菌能力也不断增强,能有效抑制细菌生长; TP浓度为2.0%时,复合膜对DPPH自由基清除率达到最大值(38.53±0.91)%;采用复合膜涂覆对圣女果能减少水分蒸腾、延缓果蔬机体衰老从而起到良好的保鲜效果,涂膜能有效延缓圣女果的腐烂和失水变质的现象,表明TP-CTS/PVA复合膜能改善果蔬的保鲜货架期和商品价值;在相同贮存时间内,当用TP浓度为1.50%复合膜涂抹圣女果时,圣女果的感官评价得分、失重率、腐烂率、可滴定酸含量、可溶性糖含量等各项指标较其他TP浓度试验组效果更好。研究表明,当TP浓度为1.5%~2.0%时制备的TP-CTS/PVA复合膜其抑菌性、耐水性、抗氧化性、以及保鲜性能等各项指标较为均衡,将其实际应用于生产中可根据需求调整TP浓度。本研究目的为探索开发抗菌抗氧化功能型复合膜和功能型包装材料替代塑料包装材料的可能性,为同时解决食品保鲜与环境污染问题提供依据。

Preparation and Fresh-Keeping Effect of Tea Polyphenol-Chitosan Composite Film

Taking polyvinyl alcohol (PVA) and chitosan (CTS) as the substrates, glycerol as the plasticizer, tea polyphenols (TP) as the functional additives, a pollution-free, biodegradable packaging TP-CTS/PVA composite film with antioxidant activity was prepared, and the effects of the concentration of tea polyphenols on the mechanical properities, antioxidant capacity, antibacterical ability, such as the influence of the physical and chemical properties, packaging film related performance were studied. The film was applied to the fresh cherry tomatoes, and the physical and chemical indexes, including sensory quality, totting rate, weightlessness, soluble sugar, titratable acid and microbial indexes during storage were analysed. The results showed that the TP-CTS/PVA composite film had both antioxidant and antibacterial effects. With the increase of TP concentration, the color of the composite film gradually darkened, when the TP concentration was 1.50%, the water solubility of the composite film was the lowest (19.85±0.64)%, and TS of the composite film was at the maximum (13.19±0.77)MPa. When the concentration of TP increase, its antibacterial ability to Escherichia coli and Staphylococcus aureus also continued to increase, it could effectively inhibit bacterial growth. When the TP concentration was 2.0%, the scavenging rate of DPPH free radicals by the composite film reached the maximum (38.53±0.91)%. The composite film coating had a good preservation effect on cherry tomatoes, effectively delaying the rot and water loss of the cherry tomatoes, and improving the shelf life and commodity value of the fruits and vegetables. In addition, during the same storage time, when a composite film with a TP concentration of 1.5% was applied to cherry tomatoes, the sensory evaluation score, weight loss rate, decay rate, titratable acid content, soluble sugar content and other indicators of cherry tomatoes were more effective than other TP concentration tests.This study showed that when TP concentration was 1.5%~2.0%, the TP-CTS/PVA composite film had balanced indicators such as bacteriostasis, water resistance, oxidation resistance and preservation performance, and the TP concentration could be adjusted according to the needs when it is applied in production. The purpose of this study was to explore the possibility of developing antibacterial and antioxidant functional composite packing films for plastic films.