| In recent years,"white pollution" caused by the plastic products has brought great harm on human life and our survival environment, at the same time also has serious threat to food safety. Therefore, seeking a new kind of material to replace plastic packaging is an important topic of "packaging and environment". According to the requirements of "twelfth five-year" development plan of environmental protection from national new material industry combined with people wishes to improve the food quality, the nano-composite edible film with a safe and fully biodegradable consumption level was developed in this study. Based on the subjects both of the food science and engineering and materials science and engineering, pea starch (PS) and peanut protein isolated (PPI) were selected as two kinds of common film substrate and starch nanocrystals extracted from waxy maize starch was added into the PS/PPI matrix to prepare the nano-composite film. The results in this study were as follows:(1) The blends of PS/PPI with different mixed ratios,100:0,90:10,80:20,70:30,60:40and50:50, may have different functional and pasting properties:1) The water absorption capacity and swelling power of PS/PPI blends decreased upon increasing incorporation of PPI, indicating that PS/PPI blended edible films may have better water resistance than pure PS films. All of the pasting parameters except for the pasting temperature showed a decreasing trend upon increasing ratio of peanut protein isolate in PS/PPI blends. The pasting temperature significantly increased from72.5℃to77.5℃and the peak viscosity, final viscosity, breakdown and setback significantly decreased.2) The hardness and cohesive-ness of PS/PPI blends gei decreased with the increasing ratio of PPI, especially when the ratio of PS/PPI reached50:50.3) Scanning electron microscopy (SEM) showed three-dimensional network of PS/PPI blends differed from the microsfructure of native heat-induced PS gel. The PS/PPI blend gels at the ratio of90:10and80:20exhibited a honeycomb feature, and the structure of PS/PPI blend gels became more loosed when the ratio of PPI in PS/PPI blends increased. The PS-PPI blend gels at the ratio of70:30showed a large fragmentary structure. Above all. filament appeared on the surface of all PS/PPI blends with different ratios of PPI, which indicated that PPI could be attached to the surface of PS gel.(2) Mechanical, barrier and morphological properties of edible films based on blends of PS/PPI plasticized with glycerol (30%, w/w) were investigated:When PPI was added into PS film at40%level, the tensile strength of PS/PPI blend films was slightly reduced but elongation increased. The water vapor permeability (WVP) and water-vapor transmission rate (WVTR) of the films dropped markedly and the smoother film surface was observed in PS/PPI blend films with the addition of PPI at40%level. Therefore, the mixed ratios of PS/PPI was60:40according to the comprehensive performance of composite films.(3) The waxy maize starch nanocrystals (WMSNC) with different adding amount of1%,3%,5%,7%and9%was added into pea starch to prepare nano-composite film. Through the study on the properties of nano-composite films, it was found that:When adding amount of WMSNC was5%, the value of the tensile strength was maximum and that of the moisture content, WVP and WVTR of the composite film was the lowest, indicating that the water resistance of film was significantly improved. The surface of the composite film with the5%adding level of WMSNC was smooth and flat and the structure of composite film was compact Therefore, the comprehensive performance of composite membrane in the add quantity of5%was best. |
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