| Active packaging is an innovative concept that incorporates antioxidants,antimicrobial agents and/or nutrients to demonstrate not only barrier properties,but also some food preservation functions.Incorporation of antioxidants into packaging materials is important,since oxidation is one of the major problems affecting food quality.Due to the health conceerns of consumers,current research in antioxidant packaging is focused on the use of natural antioxidant compounds or the use of extracts rich in antioxidants,rather than using synthetic materials.Apple peel,which is regarded as food industrial waste contains appreciable amount of polyphenols and antioxidants.But its industrial use is limited to extraction of pectin and fiber.The amount of bioactive compounds in peel is higher than juice.The main bioactive compounds present in apple peel are phenolic acids,flavonols,flavon-3-ols,anthocyanins and dihydrochalcones.Procyanidins(mainly constituted by(-)-epicatechin units),(+)-catechin,(-)-epicatechin,chlorogenic acid,phloridzin and quercetin conjugates are also found in apple peel.Therefore the objectives of the present studies were to extract and purify the polyphenols from apple peel food waste and utilize them for the development of chitosan-gelatin based active food packaging film enriched with apple peel polyphenols and study the bio-composite coatings effect on the quality parameters of strawberry fruit.Firstly,apple peel polyphenols were extracted by ultrasound-assisted extraction(UAE)and optimized conditions were determined as 32 min of extraction time,29? of extraction temperature and ethanol concentration of 56%with a yield of 35.08±0.26 mg gallic acid equivalent/g dry weights by response surface methodology.Six resins were used for the purification and D101 resin was shown the highest ratio of desorption for polyphenols and further applied for dynamic adsorption/desorption test.Furthermore,catechin,procyandin B,querecitin-3-galactoside and querecitin xyloside were identified in purified polyphenols by HPLC-MS/MS.Results demonstrate that apple peel is a valuable source of polyphenols and could be used for application in functional foods.Secondly,apple peel polyphenols(APP)were incorporated into chitosan(CS)to develop a novel functional film.The results revealed that addition of APP into CS significantly improved the physical properties of the film by increasing its thickness,density,solubility,opacity and swelling ratio whereas moisture content and water vapor permeability were decreased.Tensile strength and elongation at break of the CS-APP film with 1%APP was 16.48 MPa and 13.33%,respectively,significantly lower than those for CS control film.Thermal stability of the prepared films was decreased while antioxidant and antimicrobial activities of the CS-based APP film were significantly increased.CS-APP film with 0.50%APP concentration exhibited good mechanical and antimicrobial properties,indicating that it could be developed as bio-composite food packaging material for the food industry.Furthermore,Chitosan(CS)and Gelatin(G)based novel functional films containing apple peel nanoparticles(APNPs)were successfully produced using solvent displacement method or nanoprecipitation.Apple peel ethanolic extract(APEE)at different concentrations(5,10,15 and 20%w/w)were incorporated into the film forming solution.It was revealed by SEM that higher extract concentration provoked the formation of agglomerates of nanoparticles within the films.Fourier transform infrared spectroscopy and thermo gravimetric analysis suggested that the availability of hydroxyl groups within the polymer matrix was decreased due to the presence of apple peel related compounds.Tensile properties of the films were also influenced by the addition of APEE.Addition of APEE into CS/G significantly improved the physical properties of the film by increasing its thickness,solubility and swelling ratio whereas water vapor permeability was decreased.CS/G-APEE film with 10%APEE concentration exhibited good mechanical and,indicating that it could be developed as bio-nanocomposite food packaging material for the food industry.Moreover,chitosa(CS)based apple peel polyphenols(APP)composite coatings in improving the quality of strawberries stored at 20? and 35-40%RH was studied.To find the effects of CS-based APP composite coatings,strawberries were coated with CS,CS-APP1(0.25%APP),CS-APP2(0.50%),CS-APP3(0.75%),CS-APP4(1.0%)and stored,while the uncoated strawberries were taken as control during storing.After 6 days of storage,CS-APP2 composite coating was found very effective in decreasing the senescence and maintaining the nutritional contents of strawberries.Results of this study confirm that CS-APP composite coatings can be used to improve the quality of strawberries.Finally,to find the effects of CS/G-based APNPs composite coatings,strawberries were coated with CS/G,CS/G-APEE5(5%APEE),CS/G-APEE10(10%),CS/G-APEE15(15%)and CS/G-APEE20(20%)and stored,while the uncoated strawberries were taken as control during storing.The effectiveness of CS/G-APEE composite coatings was evaluated by measuring their weight loss,decay percentage,firmness,total phenols,titratable acidity,total soluble solids and sensory evaluation.After 6 days of storage,CS/G-APEE10 composite coating was found very effective in decreasing the senescence and maintaining the nutritional contents of strawberries.Results of this study confirm that CS/G-APEE composite coatings can be used to extend the shelf life of strawberries.Overall,findings of the present study enumerated that apple peel is a good source of polyphenols and can be successfully extracted and purified by macro-porous absorption resin.Also the purified apple peel polyphenols successfully utilized for the development of chitosan-gelatin based active food packaging film nith good antioxidant properties and better film properties.Further,edible coatings based on chitosan-gelatin polymers enriched with apple peel polyphenols showed good results for the improving of quality parameters of strawberry fruit. |
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