| Collagen,a good film-forming protein material,is widely used in food industry.However,the protein film based on collagen has some problems including insufficient mechanical strength and low barrier performance.The objective of this paper was to enhance collagen film with polyacrylate sodium and metal ions,with a focus on the interaction between collagen and polyacrylate sodium and metal ions.Importantly,the changes of collagen film properties before and after reinforcement were analyzed in order to obtain better film performance in term to tensile strength,water resistance and thermal stability.First,based on the principle of electrostatic interaction of the electronegativity of polyacrylate sodium(PAAS)and the electropositive of turgid collagen fibers in the acidic condition,a collagen composite film with PAAS(0.1?1.0wt%)was prepared and the related properties were investigated.The results showed that the PAAS addition decreased the elongation,light transparency and water vapor permeability(the minimum reached to 1.30×10-12 g·cm-1·s-1·Pa-1)of the films while increased the thermal stability.More importantly,the hybrid composite films showed higher strength that was 1.49 times of pure films.No obvious change occurred in film thickness.A compact topographic surface was obtained from SEM analyses.Compared with pure collagen and the other composites,the 0.3wt%-PAAS-composited film showed a better comprehensive properties:tensile strength,37.60 MPa,elongation,14.20%;light transparency,48.70%;and water vapor permeability,1.30×10-12 g·cm-1·s-1· Pa-1 was.Besides,some conformational changes of composite film were confirmed by fourier-transform infrared(FT-IR)spectroscopy.The aforementioned profound effects of the PAAS addition based on the electrostatic interaction indicated that the PAAS addition appropriately can effectively improve collagen film performance.Following it,Ca2+,Fe3+ and Ag+ were used to improve the properties of Co-PAAS blend films.After a general pre-experiment,the concentration gradient of three metal ions was determined as 0.001 mol/g,0.002 mol/g,0.003 mol/g,0.004 mol/g,respectively.The results showed that the treatment of 0.003 mol/g Ca2+(33.46 MPa),0.002 miol/g Fe3+(33.88 MPa)and 0.001 mol/g Ag+(45.11 MPa)increased tensile strength and decreased elongation at break of the composite films.And the thermal stability of composite films improved:the 0.004 mol/g Ag+-composited film has the highest melting temperature(97.37 ?),followed by the 0.004 mol/g Fe3+-composited film(85.39 ?)and the 0.004 mol/gCa2+-composited film(85.92 ?).The results of water vapour permeability(WVP)and film solubility appeared similar,which both decreased with the increase of concentration of Ca2+ and Fe3+.A optimal value was obtained in the 0.001 mol/g Ag+composite film.Film thickness increased when Ca2+,Fe3+ and Ag+ were incorporated.Furthermore,it can also be seen from the scanning electron micrograph of the composite film that the film structure were compact and intense at the lower concentration Ag+composite film(0.001 mol/g),the moderate concentration(0.003 mol/g and below)of Ca2+composite film and Fe3+ composite film.In addition,the incorporation of Ca2+,Fe3+ and Ag+ caused the intermolecular interaction and molecular conformation changed in the Co-PAAS blend film matrix by Fourier transfrm infrared spectroscopy(FTIR).Also,metal ions disrupted the crystallization of collagen by XRD.This indicated that metal ions had a certain effect on the Co-PAAS composite films.Therefore,Ca2+(0.003 mol/g and below),Fe3+(0.003 mol/g and below)and Ag+(0.001 mol/g)at a moderate concentration could be used as a potential alternative to improve the properties of Co-PAAS composite films.In summary,the incorporation of a certain proportion of sodium polyacrylate,iron,calcium and other metal ions expectedly improved the comprehensive performances(mechanical properties,barrier properties,thermostability and so on)of collagen films,providing a great potential application in edible packaging especially for collagen film. |
PDF Full Text Request