Study On The Properties Of Polyphenol Chitosan Composite Membrane Of Apple Young Fruit And Its Preservation Effect On Fish Meat

In recent years,biodegradable and biobased packaging materials have been obtained a widespread interest due to the limited natural resources,food safety and environmental problems caused by the use of petrochemical-based plastics.Some carbohydrate polymers,like starches,cellulose derivatives and chitosan that are biodegradable and edible substances,have been utilized as packaging materials targeting to extend food shelf-life.Moreover,considerable researches have also focused on the addition of natural antimicrobial agents extracted from agricultural commodities and food product wastes into edible packaging materials.Polyphenols,secondary metabolites produced by plants,exhibit a wide range of physiological properties,such as anti-allergenic,anti-artherogenic,anti-inflammatory,anti-microbial,antioxidant,anti-thrombotic,cardioprotective and vasodilatory effects.At present,China has become the biggest apple producing and trading country.It is very necessary to remove excessive fruitlets from apple trees,and approximately 1 million tons of young apples are thinned in the field every year in China.Thinned-young apple is rich in polyphenols,and the application of thinned-young apple polyphenols(YAP)in bio based packaging materials can effectively improve the utilization rate of apple fruit,which not only enhances the biological function ofbio based packaging materials,but also increases the economic benefits and reduces environmental pollution.Grass carp is one of the most common freshwater fishes,which can be produced about 4.2 million tons a year in China.However,the development of process and preservation of freshwater fish in China is relatively backward.Hence,the aim of this work was to prepare and characterize the chitosan film incorporated with YAP and analyze the effect of YAP on the physical,mechanical and bioactive properties of the film to determine if the YAP-chitosan film has a potential as an active packaging material The application of YAP-chitosan film on the grass carp was also studied to provide a theoretical basis for development of YAP-chitosan film.The main methodologies and results are described as follows:1.HPLC was used to detect polyphenol.The content of total polyphenols in YAP was 89.67%,in which chlorogenic acid accounted the most for 30.49%,followed by epicatechin(25.13%)and phlbridzin(16.92%).There was a small amount of procyanidins B2,quercetin-3-galactoside,quercetin-3-rhamnoside,caffeic acid,quercetin and rutin.The antioxidant activity of polyphenols in YAP was determined,and it has strong antioxidant activity,which means it is a natural antioxidant.2.The physical properties,mechanical properties,antioxidation and antibacterial properties of chitosan films with 0.25%,0.50%,0.75%and 1.0%YAP were studied.The results showed that the addition of YAP significantly(p<0.05)improved film thickness,density,degree of swelling,solubility and transparency.However,the water content,water vapor permeability and mechanical properties significantly decreased(p<0.05).Polyphenols were well-distributed into the chitosan matrix.The DPPH·scavenging activity significantly(p<0.05)increased with the addition of YAP.YAP-chitosan films had the concentration-dependentantimicrobial activities against bacteria and moulds,but no activity against yeasts.According to the inhibition and growth zone diameters,the orders of the antimicrobial activities of YAP-chitosan film against bacteria and moulds were E.coli<S.aureus<L.monocytogenes and C.fructicola<B.dothidea<A.Tenuissima,respectively.3.FTIR spectroscopy,X ray analysis,NMR analysis and thermal analysis were performed to investigate the intermolecular interaction between chitosan and YAP.FTIR spectroscopy and NMR results conformed to the results of FTUR that the two compounds might interact through non-covalent forces.X ray analysis showed YAP induced a conversion of chitosan films from crystalline to an amorphous structure.The addition of YAP had negative influence on thermal stability of chitosan films.4.The effects of YAP-chitosan films on the quality of grass carp during storage were investigated.YAP-chitosan films can maintain the quality and extend the shelf life of freshwater fish.5.Texture,surface structure,color,protein content,amino acid content of grass carp were determined.The results showed YAP-chitosan films can significantly delay the decline of grass carp texture characteristics and prevent the degradation of protein and delay the deterioration of grass carp.In conclusion,YAP-chitosan film has strong antioxidant activity and antibacterial properties,which means it can be used as packaging materials,extending the shelf life of food,improving safety and function of food.It has a wide application prospect in food industry.