天然花青素提取物与壳聚糖明胶复合膜的制备和表征

为了开发天然的抗氧化活性包装材料，以紫甘蓝、黑米、玫瑰、蓝莓为原料制备天然花青素提取物与壳聚糖明胶的复合膜，比较分析了不同天然花青素提取物对复合膜的物理、机械、抗氧化活性及形貌结构的影响。结果表明：天然花青素提取物的加入，增加了膜的厚度，显著（P<0.05）影响膜的含水率、水溶性及外观形貌。壳聚糖明胶复合膜的水蒸汽透过率（water vapor permeability，WVP）为10.69×10-11 g/(m·s·Pa)。玫瑰花青素提取物的加入使得WVP值降低，而其他花青素提取物的加入使得WVP值增大。玫瑰复合膜的拉伸强度最大，达到27.03 MPa，断裂伸长率最小，黑米花青素提取物可增加复合膜的延展性，断裂伸长率最大为57.67%。傅里叶红外光谱表明天然花青素提取物的羟基基团与壳聚糖的氨基基团产生相互作用。扫描电镜结果表明花青素提取物影响微观结构，而且生物相容性较好。加入天然花青素提取物后，复合膜抗氧化活性均显著（P<0.05）提高，且玫瑰复合膜有着较高的抗氧化活性，1,1-二苯基-2-苦基肼（DPPH）自由基清除能力达到95.47%。结果表明：玫瑰花青素提取物更有利于开发阻湿性能好，水溶性低，抗拉伸和抗氧化活性高的包装材料，具有良好的应用前景。

Preparation and characterization of chitosan/gelatin composite films incorporated with four natural pigments

Abstract: In order to obtain antioxidant active packaging materials, chitosan/gelatin (CG) composite films incorporated with 4 kinds of natural pigments were developed. The 4 kinds of natural pigments were extracted from red cabbage, black rice, rose and blueberry, respectively, and the anthocyanins content in each pigment was measured. The films were prepared by casting and solvent-evaporation method. The composite film-forming solutions were prepared by dispersing chitosan (1%) in the aqueous solution of 0.5% glacial acetic acid mixed with 1% gelatin at the volume ratio of 7:3. As for the film, the final concentration of anthocyanins in the film was established as 25% of the total volume of the mixture of hydrogels. The physical, mechanical, antioxidant and structural properties of the composite films were also investigated. Physical and mechanical properties of the films showed that the CG film had a lower water-vapor permeability (10.69×10-11 g/(m·s·Pa)) when not incorporated with natural pigments. The incorporation of rose pigments led to the reduction of the water-vapor permeability while the other extracts did inversely. The lowest water-vapor permeability value was 10.05×10-11 g/(m·s·Pa) and the incorporation of blueberry pigment reached the maximum level of 14.52×10-11 g/(m·s·Pa). Furthermore, the addition of rose pigment led to a reduction of elongation at break but an increase of tensile strength, with the lowest elongation at break of 37.66% and the greatest tensile strength of 27.03 MPa. However, black rice pigment extract led to an increase of elongation at break from 52.59% to 57.67% compared with CG film without incorporating natural pigments. Fourier transform infrared spectroscopy (FTIR) showed that the incorporation of natural pigments brought about the interactions between its hydroxyl groups and the amino groups of chitosan. Significant structural transformation could be observed from scanning electron microscope (SEM), and each film showed homogeneous surfaces without pores and with excellent structural integrity, indicating a high compatibility between the components. DPPH (1,1-Diphenyl-2-picrylhydrazyl radical 2,2-Diphenyl-1- (2,4,6-trinitrophenyl)hydrazyl) radical scavenging activity assay was selected to evaluate the antioxidant activity of the films. The antioxidant activity of the films increased significantly with the addition of natural pigments. The film incorporated with rose pigment showed a higher antioxidant activity whose DPPH radical scavenging activity reached 95.47%, while the incorporation of black rice pigment led to a lower antioxidant activity of 39.98%. Moreover, the addition of natural pigments caused significant changes in moisture content, water solubility, thickness and color. The incorporation of red cabbage extract increased the film''s moisture content and water solubility compared with CG film without incorporating natural pigments, which reached their maximum levels of 23.56% and 28.42%, respectively. Natural pigments exist in a wide variety of flowers, vegetables and fruits, it is available and inexpensive. The results indicate that incorporating natural pigments with CG film is a feasible way to develop new composite film for active packaging.