南瓜皮粗多糖/壳聚糖复合膜的构筑及性能表征

Preparation and Characterization of Crude Pumpkin Peel Polysaccharides/Chitosan Composite Films

摘要:

为实现南瓜皮废弃物的高值化利用并制备性能优化的可食性包装材料，本文从南瓜皮中提取粗多糖（PP），经含量测定和结构表征后，通过溶液浇铸法将不同添加量PP与壳聚糖共混，探究其性能调控规律。结果表明，PP中总糖含量为62.63 wt.%，多糖达52.1 wt.%，紫外-可见光谱证实其含有蛋白质等成分。随着PP添加量的增加，复合膜的厚度和溶解度显著提升，最大值分别为23 μm和56.32 wt.%，水分含量最低达15.6 wt.%，而水蒸气透过率则在PP添加量40 wt.%时达到最低15.63 g·mm·m-2·d-1·kPa-1，此时薄膜结构最为致密。力学性能结果表明，当PP添加量为60 wt.%时，复合膜拉伸强度达最大值45.1 MPa；而断裂伸长率在20 wt.%PP添加量较纯壳聚糖膜提升近3倍。结构和热性能结果表明，PP与壳聚糖存在氢键相互作用，能破坏其有序晶体结构，并改变壳聚糖膜的热稳定性。基于食品包装加工与应用需求，60 wt.%PP添加量为复合膜最优配比，此时薄膜兼具良好柔韧性、热稳定和阻隔性能，可满足生鲜食品保鲜包装要求，为南瓜皮高值化利用提供了新路径。

Abstract:

Pumpkin peel waste was targeted for high-value utilization in this study, with the aim of developing edible packaging materials of optimized performance. Crude polysaccharides (PP) were extracted from pumpkin peel waste, followed by the determination of their content and characterization of structure. Subsequently, composite films were fabricated via the solution casting method by blending chitosan with PP at different addition levels, and the law of performance regulation was investigated. The total sugar content of PP was determined to be 62.63 wt.% , with a polysaccharide purity of 52.1 wt.%. The presence of proteins and other minor components in PP was confirmed by ultraviolet spectroscopy analysis. With increasing PP addition, the thickness and solubility of the composite films were significantly increased, reaching maximum value of 23 μm and 56.32 wt.%, respectively, while the moisture content was reduced to a minimum of 15.6 wt.%. In contrast, the water vapor permeability of films was first decreased and then increased, reaching a minimum value of 15.63 g·mm·m-2·d-1·kPa-1 at a PP addition of 40 wt.%, which corresponded to the most compact film structure. Regarding mechanical properties, when the PP addition was increased to 60 wt.%, the tensile strength of the composite film was maximized at 45.1 MPa; meanwhile, the elongation at break at a PP addition of 20 wt.% was reached an approximately threefold increase compared to that of the pure chitosan film. Structural and thermal analyses confirmed that hydrogen bonds were formed between PP and chitosan, leading to the disruption of the ordered crystalline structure of chitosan and alterations in the thermal stability of the composite films. Based on the requirements of food packaging processing and application, 60 wt.% PP loading serves as the optimal ratio for the composite film. At this ratio, the film exhibits excellent flexibility, thermal stability and barrier properties, which can meet the requirements of fresh-keeping packaging for fresh food, thus providing a novel approach for the high-value utilization of pumpkin peel.