Study On Soy Protein-Based Composite Edible Films

Edible films have received great interest in food preservation and been used widely. Interest and research activity in soy protein isolate (SPI)-based film have been especially intense all around the world. In this work, the effect of blend-modification of lipids and polysaccharides on barrier and mechanical properties of composite film was examined. In addition, the performance of edible film at different environment conditions was also evaluated, and finally, practical application of SPI-based film in coating of fresh-cut apple was investigated.Blend-modification of soy protein isolate solutions with beeswax and lauric acid (La) to has been used to form SPI/lipid emulsion edible films. Significant reduction in permeability of water vapour and oxygen could be achieved upon addition of BW and La. Water vapour and oxygen permeability of SPI films decreased by 29.6% and 68.3% respectively with addition of La, and reduction by 23.7% and 66.0% was shown with addition of BW. Mechanical properties, water solubility and transmission were also influenced by lipid addition. Overall, option lipids addition of 0.02-0.1g/gSPI gave the best results. For improving the performance of edible film, two approaches, co-dring preparation and direct addition, were studied to modify SPI and SPI/La film by blending with polysaccharide (propyleneglycol alginate, pectin, carrageenin and aloe polysaccharide). The most significant improvement was observed through blending with propyleneglycol alginate(PGA), and co-drying preparation showed better result than direct addition. SEM analysis showed that Microstructures of the films is the basis for the differences in their barrier and mechanical properties of blend-modification among SPI, polysaccharides and lipids.Changes in the relative humidity and temperature of environment may affect performance of SPI-based films differently. Comparing moisture barrier properties at different relative humidity, films with addition of La showed slight relation with relative humidity and SPI/La/PGA2 film made from co-drying blend showed the slightest relationship with relative humidity. But the barrier properties of edible film including La were affected by environment temperature significantly. The effects of La content, relative humidity and temperature on water vapor permeability, oxygen permeability, tensile strength, percentage elongation were evaluated using regression analysis. The most important factors influencing water vapor permeability and oxygen permeability were relative humidity and temperature respectively.The degree of browning of apple flesh, weight loss of the fresh-cut apple of the...