Study On Modified Soy Protein Isolate Film Processing And Properties

Soy protein isolate (SPI)-based film materials is the use of agriculture-derived biopolymer composite materials used in certain applications,particularly short-term applications, such as food packaging, with goodprospects. Soy protein has been widely studied due to its low cost, availability,complete biodegradability, and high barrier properties against both oxygenand oil at low relative humidity. However, there are two inherent problemslimiting usage of pure SPI films, namely inadequate mechanical properties andrelatively high moisture sensitivity. In order to improve the inadequateapplication of the SPI-based materials, this article will use the physical,chemical modification to change the network structure and chemical bond ofthe SPI molecules, and to expect to be able to be applied in packagingmaterials, food packaging and other aspects. This article focuses on: studypreparation of soy protein isolated (SPI) film physical conditions and materialcomposition; reductant cysteine (L-cys), surfactant sodium dodecyl sulfate(SDS) and lubricants calcium stearate (CaSt2); modify SPI and systematicstudies; polycaprolactone (PCL)-coated SPI films were prepared by dippingSPI film into PCL solution.(1) The mechanical and water barrier properties of SPI film have beenimproved by heat, alkali and ultrasonic treatment. Glycerol (gly) improved theflexibility of SPI film, but increased the water sensitivity of SPI film, theoptimal dosage is50%by weight of SPI powder. L-cysteine enhanced the water barrier properties and thermal stability of SPI film, thermal degradationtemperature (Td) increased12, the optimal dosage is8%by weight of SPIpowder.(2) SPI films were modified by the using of anionic surfactant sodiumdodecyl sulfate (SDS) and heat stabilizers stearic acid calcium (CaSt2). Themechanical and water barrier properties of SPI film improved by SDSmodified. When SDS dosage is30%by weight of SPI powder, the elongationat break (E%) increased by238%, water vapor permeability (WVP) reducedby21%. CaSt2had two types of structural in the film, in which the ions formas the main structure, it can react with SPI. The mechanical and water barrierproperties of SPI film improved by CaSt2modified. When CaSt2dosage is12%by weight of SPI powder: E%increased by292%; WVP reduced by40%.DMTA showed that SDS enhanced the compatibility of CaSt2and SPI. TGAshowed that thermal stability of MSPI films had been enhanced, the thermaldegradation temperature (Td) has been increased by20.SPI films were homogeneously coated on both sides by being dipped intoa specified solution of PCL. The surfaces of coated films were more smoothand glossy compared with those of uncoated SPI films. The mechanicalproperties and water barrier properties of the composite film were enhanced;TS increased by40%, water-blocking performance improvement of60%; andthe thermal performance were improved, the Tdaverage increased by15℃.