| Food packaging films based on natural biological macromolecules have the advantages of safety,no pollution and degradation.Previous studies have found that anthocyanins have good sensitivity in pH color rendering,which can be used to make food packaging with indicator function.In this study,solvent extraction method was used to obtain anthocyanin-rich extracts from 14 kinds of fruits and vegetables.Starch,locust bean gum,chitosan,carrageenan and polyvinyl alcohol(PVA)were used as matrix to prepare polysaccharide-PVA-anthocyanins blending films by plate casting method.The effects of different sources of anthocyanins and different types of polysaccharides on the structural physical and functional propertier of the films were studied.The main results were as follows:(1)The effects of anthocyanins from different plant sources on film structure,physical properties and functional properties were studied.There were no significant differences in thickness and water vapor transmittance(WVP)among all films(p>0.05).FT-IR spectra showed that the anthocyanins mixed compatibility with the matrix.XRD spectra showed that the addition of most kinds of anthocyanins had little effect on the crystallinity of the blending films.Scanning electron microscopy(SEM)showed that some kinds of anthocyanins improved the phase separation of the substrate slightly.The pH-sensitive of films varied greatly due to the different content and composition of anthocyanins.In the normal temperature spoilage experiment of pork,the color of the starch-PVA-anthocyanin film added with the anthocyanins of Lycium barbarum(SP-LRA),purple cabbage(SP-PCA)and purple potato(SP-PSA)changed obviously,which could be used to indicate the freshness of pork.The starch-PVA-anthocyanin film added with black eggplant peel(SP-BEPA),SP-LRA and SP-PCA could be used to indicate the freshness of shrimp.Therefore,the four anthocyanins(Lycium barbarum,purple cabbage,purple potato and eggplant peel anthocyanins)can be screened for further research.(2)The effects of different types of polysaccharides on the structure,physical and functional properties of polysaccharide-PVA-anthocyanin blending films were further studied.There was no significant difference in thickness and WVP between the films based on three substrates(p>0.05).Chitosan film had the highest water content,and locust bean gum film had the highest solubility.When the same amount of anthocyanins was added to the matrix with different ionic characteristics,the films showed a great difference in appearance,which affected the light barrier performance of the films.In terms of mechanical properties,chitosan and locust bean gum films had higher elongation at break,but lower tensile strength in the three kinds of polysaccharides-PVA-anthocyanins blending films.Carrageenan-PVA-anthocyanin blending film had the highest TS value and the lowest EAB value,indicating that the film was strong but brittle.FT-IR,XRD and SEM images showed that the polysaccharide matrix,PVA and anthocyanins were well mixed,and no phase separation appeared.In the experiments of pH sensitivity and volatilization of ammonia,carrageenan-PVA-anthocyanin blending films showed the best sensitivity,while locust bean gum-PVA-anthocyanin blending films exhibited a better color development.In addition,locust bean gum-PVA-black eggplant peel anthocyanin blending film(LGP-BEPA film),locust bean gum-PVA-purple sweet potato(LGP-PSA film)and carrageenan-PVA-black eggplant anthocyanin film(CGP-BEPA Film)can be used to monitor shrimp freshness. |
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