Development Of Chitosan-Soybean Protein Isolate Edible Films With Antimicrobial Properties

The traditional food packaging material,usually on the basis of meeting the food packaging requirements,can easily cause environmental problems such as a large number of "white pollution".The migration of harmful processing aids in food packaging materials poses a serious threat to human health.Therefore,the development of safe,environmentally friendly,biodegradable new packaging materials is the future trend.In this study,chitosan and soybean protein isolate(SPI),which have a wide range of sources,low price and good biodegradability,were used as the basic raw materials.On the basis of studying the film forming process,the biodegradable bacteriostatic film was prepared by adding bacteriostatic substances.In order to provide theoretical and data support for safe,environmentally friendly and biodegradable new packaging materials.The more dry matter in the film-forming solution,the thicker the chitosan-SPI basic film is.With the increase of SPI content,the tensile strength and elongation at break of chitosan-SPI basic films increased gradually,WVP value first decreased and then increased,solubility first increased and then decreased.When the concentration of SPI was 0.8%(w/v),the WVP value was the lowest(0.193 ±0.062 g·mm·m-2·h-1·Kpa),and the solubility was the highest(28.17±2.71%).The tensile strength of chitosan-SPI basic membrane was negatively correlated with glycerol concentration,while the elongation at break and WVP value were positively correlated with glycerol concentration.The solubility of chitosan-SPI basic film was not significantly affected by glycerol concentration(p>0.05).With the increase of drying temperature,the tensile strength of the base film decreased gradually,and the elongation at break increased first and then decreased.The maximum tensile strength was 43.876 ±2.220%when the drying temperature was 55 ?.Drying temperature has little effect on WVP value and solubility.When drying temperature is 60 ?,WVP value and solubility are slightly higher than those of other groups.Taking WVP value as an index,the basic process of forming water-resistant composite membrane with SPI concentration of 0.67%(w/v),glycerol concentration of 0.5%(v/v)and drying temperature of 53 ? was optimized by response surface method.The antibacterial effect of antibacterial films on Staphylococcus aureus and Escherichia coli increased with the increase of ?-polylysine concentration.When the concentration of Nisin was 0.2%(w/v),the composite membrane had the best antibacterial effect on Staphylococcus aureus.Taken into account,the optimal addition of ?-polylysine is 0.3%(w/v).The addition of Nisin increased the antibacterial effect on Staphylococcus aureus,but had no significanteffect on Escherichia coli(p>0.05).When the concentration of Nisin was 0.2%(w/v),the composite membrane had the best antibacterial effect on Staphylococcus aureus.When the concentration of Nisin was 0.5%(w/v),the elongation at break reached the maximum(121.977±5.024%),which was 68.7% higher than that of the antibacterial film without Nisin.With the increase of Nisin concentration,the water vapor transmittance and solubility of the film increased,while the water resistance decreased.According to all the indexes,chitosan-soybean protein isolate membrane forming process was determined to be 0.67% SPI,0.5% glycerol,0.3% ?-polylysine,0.2% Nisin(w/v)and the drying temperature is 53 ?.