Properties And Mechanism Of Transglutaminase-Crosslinked Soy Protein Isolate-Gelatin Edible Film

In recent years,biodegradable bio-based packaging materials have gradually attracted the attention of scholars.Soy protein isolate(SPI)is cheap and easy to obtain,and it is easy to form a film.However,a single SPI film has poor properties.In this experiment,SPI was used as the substrate to investigate the effect of Gelatin(GEL)and transglutaminase(TGase)on the properties of films and its mechanism.The main results were as follows:(1)Firstly,the effect of SPI concentration on the properties of film was explored,the mechanical properties,light transmittance and barrier properties of the film were investigated.It was found that the properties of the film was best when the SPI concentration was 5%.The tensile strength(TS)of the film was 5.65 MPa and the elongation at break(EB)was 33.8%.The water vapor permeability(WVP)was 19.3g·mm/d·m~2·KPa,which was 26.81%lower than 26.37 g·mm/d·m~2·KPa at 2%protein concentration.The peroxide value(POV)also decreased from 41.40 meq/kg to 29.62meq/kg,and the transmittance was 71.94%.(2)Secondly,the effect of GEL addition amount on the performance of SPI film was investigated.It was found that the TS and EB increased by 32.89%and 15.03%compared with SPI film when the addition was 0.4%.WVP and POV decreased by 33.73%and26.37%,respectively.The transmittance increased.The average particle size and viscosity of SPI/GEL film forming solution were larger,which might be due to the enhancement of intermolecular and intramolecular forces.The water contact angle(CA)of composite film with 0.4%GEL was 72.13°,43.26%higher than that of SPI film,indicating a stronger hydrophobicity.Fourier transform infrared spectroscopy(FTIR)showed that the hydrogen bond interaction between the molecules was enhanced,the microstructure was smoother,and the thermal stability was the strongest.(3)Then,the effects of TGase addition on the performance of SPI/GEL film were investigated.When the addition amount was 3 U/g,the TS and EB of TG-SPI/GEL film increased by 30.44%and 25.60%compared with that of SPI/GEL film.WVP and POV decreased by 34.83%and 22.92%.Cross-linking led to the formation of larger protein molecules and an increase in the viscosity of the film forming solution.The CA was increased to 80°,and the hydrophobicity was further enhanced.The microstructure was more uniform,and the thermal stability was stronger.It might be that TGase further promoted the development of molecular structure,and the interaction was stronger.(4)Finally,SPI film,SPI/GEL film and TG-SPI/GEL film were applied to the preservation of potatoes in the form of film forming solution immersion and film wrapping,and fresh cut potatoes without treatment were taken as the control.The results showed that the preservative effect was best after adding TGase,and the effect of impregnation was better.After 5 days,the activities of PPO and POD were only 0.62 U/min·g and 0.74U/min·g,which decreased by 31.87%and 29.82%compared with the control group,respectively.The intensity of browning was only 3/5 of that of the control group,and no odor was produced.The sensory score was higher.In conclusion,GEL and TG enhanced the comprehensive performance of SPI film.The research results could provide a theoretical basis for the development of edible film and research ideas for the preservation of fruit and vegetable food.