Developments Of Multiple Functional Zein-based Films: Preparation,Microstructures And Properties

Zein,the major co-product of the oil and rapidly growing bioethanol industries,is a water-insoluble prolamin present in corn endosperm cells with a high content of hydrophobic amino acids(leucine,proline,and alanine).In recent years,modifications are carried out to make zein films satisfied performance requirements in application,such as strengthening the mechanical properties,antioxidant and antimicrobial properties,enhancing the hydrophilic/hydrophobic properties,improving the oxygen/water vapor barrier,heightening the drug-loaded control and release.However,it still needs to be further studied in preparation methods,mechanisms and applications of zein films.In this work,a novel method to evaluate protein solubility was proposed,zein-based films with antimicrobial and antioxidant activities were prepared by appropriate preparation methods using suitable emulsifiers,antimicrobial and antioxidant agents,great efforts were focused on the relationships among preparation methods,microstructures and properties.(1)Development of a method for fast assessment of protein solubility.Basing on the mechanism of protein dissolved,a method for fast assessment of protein solubility was proposed,which mainly involves ultrasonic dispersion,differential centrifugation,spectral measurement(UDDCS)and curvature estimation.The results show that the relationship between the standard deviation and the protein concentrations originally added accords with the modified exponential equation,and the corresponding concentration of the maximum curvature point is defined as the solubility of protein.Lysozyme solubility data in NaCl aqueous solutions and zein solubility data in ethanol aqueous solutions are selected to verify the UDDCS method by comparing the data obtained by the UDDCS method and the results from references,and the results indicate that the UDDCS method is universal and time-saving.(2)Development of edible zein-based film with antimicrobial and antioxidant activity.Edible zein-based films with antimicrobial and antioxidant activity were developed by blending zein with lysozyme(LY)and ascorbic acid(AA)in the presence of polyethylene glycol 400(PEG 400),and the physico-chemical properties and release profiles were performed to characterize the developed zein-based films.The results of mechanical testing showed that the elongation at break of zein-based films containing PEG 400,AA and LY showed 13.5-34.5 and 2-3 times higher than the controlled zein film and zein-PEG 400 film respectively.And the addition of AA and PEG 400 had the synergistic effect to plastify zein-based films.he release tests indicated that the release profiles of LY and AA from zein-based films could be modulated by changing the concentrations of AA and LY,when at low concentration of AA,the release rate of LY and the total LY release decreased by 33.7% and 19.4% individually and he release rate of AA was 1.5 times higher than that without LY,and total AA release increased from 52.3% to 84.5%.The differences in LY and AA release profiles from zein-based films were attributed to the hydrophilic properties of AA and LY,the change in the hydrogen bonding of AA and LY with the zein matrix,and the inner microstructure of zein-based films.An antimicrobial activity of up to 58898 ± 635 U/cm2 of antimicrobial zone area and an antioxidant activity up to 159 ?mol Trolox/cm2 were found for the developed zein-based films.(3)Effects of emulsifiers on controlled release properties of zein-based films.To develop edible films with controlled release properties for multiple bioactive compounds,the morphology and release profiles of zein-based films were modified by blending zein with emulsifiers like sodium alginate(SA),Soy Lecithin(SL)and Pluronic F-68(F-68)in the presence of polyethylene glycol 400(PEG 400).The physico-chemical properties and release profiles of the zein-based films were performed to characterize the developed zein-based films.The zein-based films containing 10% of SL,10% of F-68 and SL/F-68 showed 1.87-,1.65-,and 7.5-fold lower initial release rates than the zein film without emulsifiers for the model antimicrobial agent lysozyme(LY)respectively.Meanwhile,the zein-based films containing 10% of SL and SL/F-68 showed 0.6-fold lower initial release rates than zein film without emulsifiers for the model antioxidant Ascorbic acid(AA)respectively.It was very evident that the simultaneous use of SL and F-68 in blending film could significantly improve the effects of sustained release of LY and AA,and heighten the antioxidant and antimicrobial activities of zein films.The blend films showed antilisterial activity to 22971 ± 1140 U/cm2 of antimicrobial zone and antioxidant activity up to 226 ?mol Trolox/cm2.(4)Preparation and characterization of zein/cellulose nano/microparticles.Using antisolvent and coprecipitation method,mixed nanoparticles of zein/cellulose containg different weight ratios were prepared by spraying the solution of zein/cellulose into 0.5 M of H2SO4 aqueous solution,and the nanoparticles were characterized by SEM,TGA,XRD and FT-IR.The results showed that when the weight ratio(g :g)of zein/cellulose is between 1.00 : 0.00 and 0.70 : 0.30,zein and cellulose have good compatibility,and the yield and redispersion of them is apparently higher than that of pure zein nanoparticles,which has good potential in applying for drug controlled release investigation.Meanwhile,the results of TG indicated that with the increase of cellulose addition,the content of PF-68 contained in prepared samples gradually decreased,which demonstraed that the weight ratio of zein and cellulose has proportions required by the hydrophobic and hydrophilic chains of PF-68.