| In order to solve the increasingly serious environmental problems caused by non degradable plastic packaging materials,environmentally friendly packaging films based on biological macromolecules have become a hot topic in food packaging.Adding plant derived active ingredients such as polyphenols,flavonoids,and natural pigments to biological matrix films to prepare multifunctional packaging materials is an important development direction for functional degradable membranes.Rosa King Glory is one of the main edible rose varieties in China,which contains a large amount of polyphenols.However,there is currently limited research and application on it.In this paper,sodium alginate and gelatin were used as film forming substrates,and rose polyphenol extractions were added to prepare films with antioxidant function,which were further applied to the encapsulation of sunflower seed oil and lard,in order to provide new ideas for the new packaging of edible oils and the application of plant polyphenols.The main research findings of the paper are as follows:(1)Firstly,polyphenols were extracted from Rosa King Glory,and the composition of rose polyphenols extractions(RPE)were analyzed by LC-MS to evaluate its temperature and p H stability.Six common antioxidants were used as reference materials to evaluate their antioxidant ability through free radical scavenging ability,iron ion reduction ability,and metal ion chelation ability.The results showed that after extraction,purification,and freeze-drying,the total phenolic content in RPE was 85.43%.The mass spectrometry results indicated that there were mainly 8polyphenols in RPE,including cyanidin-3,5-diglucoside,ellagic acid,catechin,quercetin,myricetin,kaempferol,bis hexahydroxydiphenyl glucoside,and gallic catechin.RPE is relatively stable at p H ≤ 4 and temperature ≤ 20℃.RPE had a strong ability to scavenge ABTS and DPPH radicals.For example,at the concentration of 0.1 mg/m L,the scavenging rates of RPE on 0.14mmol/L DPPH radicals and 7 mmol/L ABTS radicals were 89.53% and 100%,respectively.At the same concentration,its antioxidant capacity was superior to vitamin C,gallic acid,α-Tocopherol,butylhydroxyanisole,butylhydroxyanisole,and tea polyphenols;its metal ion chelating ability is superior to α-Tocopherol,butylhydroxyanisole,butyl hydroxyanisole,and tea polyphenols,but not as good as EDTA.(2)Secondly,gelatin and sodium alginate were used as the film forming matrix,and RPE(0.1～0.4 mg/m L)was added to prepare the antioxidant film.The mechanical properties,physical properties and oxidation resistance of the film were analyzed.The results showed that compared with the single gelatin film/sodium alginate film,the mechanical properties and barrier properties of gelatin sodium alginate composite film were enhanced,and the comprehensive performance of the film was the best when sodium alginate: gelatin=7:3.When RPE was added to the film forming solution,the uneven distribution of RPE over 0.2 mg/m L in the film led to a decline in the mechanical properties of the film,but the color of RPE could enhance the light barrier of the film,and the gelatin-sodium alginate-RPE active film showed good antioxidant activity.When the RPE concentration is 0.4 mg/m L,the membrane has a scavenging rate of85.92% and 100% for DPPH and ABTS free radicals,respectively.The release rates of RPE in water,50% ethanol,and 95% ethanol were first fast and then slow,and after 240 hours,the release of RPE in water was 69.63% higher than that in 95% ethanol solution.(3)Finally,gelatin-sodium alginate-RPE functional film was applied to edible oil packaging.At 20℃,polyethylene plastic packaging was used as a blank control,and its packaging effects on lard and sunflower seed oil were investigated in two forms: direct-contact packaging and headspace packaging,to evaluate its protective effect on oil.The results showed that the shelf life of sunflower oil was extended by 109.71 days and 77.18 days respectively by direct contact and headspace packaging films,and the shelf life of lard was extended by 71.29 days and 28.02 days respectively.During 4-week storage period,both packaging methods can enhance the oxidative stability of lard and sunflower seed oil,reducing the acid value,peroxide value,thiobarbituric acid value,conjugated diene and conjugated triene values of the two oils.Moreover,direct contact packaging has a stronger effect.Therefore,gelatin-sodium alginateRPE film can delay the oxidation of oil. |
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