Study On The Grafted Modification And Application Of Soy Protein Isolate

The synthesis and application of soy protein isolate grafted copolymers have been investigated.SPI-g-PSt and SPI-g-PVAc were synthesized in 8 moL/L urea aqueous solution initiated byammonium cerous nitrate-potassium persulfate under the protection of nitrogen (N2). Further, theapplication of the soy protein isolate grafted copolymers in the field of SPI edible films was studied.SPI-g-PSt copolymer was characterized by Infrared Spectrometer, Nuclear Magnetic Resonanceand Differential Scanning Calorimetry. The results indicated the styrene has been grafted on the SPI.The influence of reaction conditions on percentage graft and percentage efficiency was investigated.The percentage graft and percentage efficiency increase at first and then decrease with the increaseof the initiator concentration, the monomer concentration and the reaction temperature. With theincrease of reaction time, the percentage graft and percentage efficiency increase.SPI-g-PVAc copolymer was characterized by IR and DSC. The influence of reaction conditionson percentage graft and percentage efficiency was also investigated. The results indicated that theeffects of reaction time, initiator content, monomer content and reaction temperature on thecopolymerzization of SPI with VAc is similar to effects of these reaction conditions on thecopolymerization of SPI with styrene.SPI-g-PSt films and SPI-g-PVAc films were prepared from the aqueous solution of SPI-g-PStcopolymers and SPI-g-PVAc copolymers. Tensile strength(TS), the elongation(E) and the watervapor permeability(WVP) of these films were determined. The influence of pH value, plastizercontent and graft ratio on the properties of films were studied. The results indicated that TS valuesof SPI-g-PSt films were higher than those of SPI films, E values of SPI-g-PVAc films were higherthan those of SPI films;the results also indicated TS and E of SPI-g-PSt films, SPI-g-PVAc filmsand SPI films increased with the increasing of pH values. The WVP values of SPI-g-PSt andSPI-g-PVAc films were lower than those of SPI films.The edible films were prepared from the aqueous solution of soy protein isolate and carboxyethylcellulose, with various concentrations of plastizer and with various carboxyethyl cellulosecontents.With the increasing of carboxyethyl cellulose contents, WVP and TS of the edible filmsincreased, E of the edible films decreased firstly and then increased. With the increasing of plastizercontents, WVP and E of the edible films increased, TS of the edible films decreased.