Development Of Antioxidant And Antibacterial Rice Protein Hydrolysate/Chitosan Film And Its Incorporation With Curcumin And ZnO Nanoparticles

The application of curcumin has been restricted due to its poor solubility,low bioavailability,chemical instability and light degradation.Food packaging is an effective delivery form for bioactive compounds.Nowadays,food packaging origin from natural edible polymers is becoming more and more popular,for reducing microbial growth and prolonging food shelf-life.Of which polysaccharide and protein are the most common-used materials.However,highly hydrophilicity and lack of mechanical strength prevent their usage in food industry.Hence,it is of great importance to address these drawbacks.In this study,the composite film was fabricated from rice protein hydrolysate and chitosan.The effect of chitosan molecular weights on the composite films were investigated.Moreover,other modifications including genipin crosslink and adding nanomaterials have been applied to improve the film performance.The results were as follows:1.The composite films were prepared by adding rice protein hydrolysate into chitosan.Effect of four different chitosan molecular weights(Mw,0.8-1.0,30,100,300 kDa)was evaluated and curcumin was further incorporated into the film to enhance its bioactivities.With increasing Mw(<100 kDa),the moisture,solubility and water vapor transmission of the films marginally decreased while tensile strength increased.All films showed extraordinary extensibility ranging from 180.26% to 204.08%.Differential scanning calorimetry confirmed Mw did affect the thermal stability.The lower MW,the higher antioxidant activity.Only film with 30 kDa exhibited noticeable antibacterial activity against E.coli and S.aureus.Curcumin effectively improved both antibacterial and antioxidant activity.Hence,chitosan molecular weight must be chosen carefully according to its application and incorporation of protein hydrolysate into film would be an efficient strategy to modify film performance.2.The composite film was fabricated by crosslinking rice hydrolysate and chitosan using genipin(GP)at different concentrations and curcumin was further incorporated to enhance its bioactivities.The ζ-potential of GP-crosslinked film-forming solution was higher than the control.The particle size first decreased and then increased with GP concentration ranging from 0.2 mg/g to 1.0 mg/g.GP decreased the water vapor transmission but did not significantly affect solubility of the crosslinked films.GP 0.4mg/g film had the lowest moisture content and water vapor transmission.Besides,GP crosslinking increased the mechanical elongation,breaking-force and thermal stability,but decreased DPPH scavenging activity due to crosslinking of antioxidant peptides.Notably,curcumin immensely increased DPPH scavenging activity and antimicrobial activity.Curcumin-loaded films had higher antibacterial activity against S.aureus than E.coli.3.Transparent films were obtained by the solution casting method from chitosan and rice hydrolysate,reinforced with different cellulose nanocrystals(CNC)contents(0%,3%,6% and 9%).The influence of different CNC loadings on the mechanical,thermal,barrier,optical,and morphological properties was discussed.SEM showed the formation of intramolecular interactions between the CNC and proteins that lead to more compact and homogeneous films.These interactions had a positive influence on the mechanical strength properties,which is reflected in higher breaking force and extensibility than 0% CNC film while resulting in stiffer films as the CNC content increases.Thermal stability of the films was also improved with the presence of CNC,by increasing maximum degradation temperature with increasing CNC contents.The linkages formed between the CNC,and proteins reduced the water affinity of the reinforced films,leading to a reduction in their moisture content,water solubility and water vapor transmission.The present work shows the possibility of obtaining CNCreinforced films with improved mechanical,thermal and barrier properties and the loaded ZnO nanoparticles increased the antibacterial properties of the films.