Preparation And Bioactivity Of Astragalus Total Flavonoids And Its Application In Retain Apple Juice Freshness

Astragalus is mainly produced in north China,is the legume root of Mongolian Astragalus and membrane pod dry root,has been included in the list of medicinal homologous substances,application space will be broader,the Astragalus is widely used in the field of medicine,rarely used in the field of food,so the research of Astragalus plant resources has important practical significance.Flavonoids are important polyphenols and Astragalus flavonoids is one of the main active components of Astragalus.This paper optimizes the extraction process parameters of Astragalus total flavonoids,after purification treatment,studies the antioxidant resistance,composition,stability and application in apple juice preservation,providing basic data and technical support for the research and development of natural food additives and expanding its application scope.The following is the specific research content of this paper:1.The paper uses Mongolian Astragalus as the raw material and total flavonoids extraction amount as the evaluation index,using ultrasonic assisted solvent method of total flavonoids extraction,the optimal extraction process is extraction temperature70℃,ethanol volume fraction 80%,extraction time 100 min,solid-liquid ratio 1:25(g/m L),ultrasonic power 140 W,The maximum amount of total flavonoids extraction under this condition was 7.4 mg/g.2.The antioxidant activity of purified Astragalus total flavonoids and the antioxidant activity of Astragalus flavonoids in ethanol eluents with different volume fractions was studied.It was found that the scavenging rate of DPPH free radicals was similar to that of Vc when the mass concentration of purified Astragalus total flavonoids was 0.28 mg/m L,can reach 87%.When its mass concentration was 1.4 mg/m L,the scavenging rate of hydroxyl radicals reached 100%;the flavonoids in 50% ethanol eluent had the strongest ability to scavenge DPPH.Astragalus total flavonoids before purification also have a significant scavenging effect on DPPH free radicals and hydroxyl radicals,and have a certain reducing power,which can reach about 50% of Vc within the selected concentration range.3.The components of Astragalus total flavonoids were analyzed by HPLC,it was detected that the purified samples were mainly composed of four components: calycosin,calycosin glycoside,formoononetin and ononin,the relationships between its antioxidant capacity and its components were explored.Infra R spectroscopy showed that the samples coincided with flavonoids.Electron microscope scan results show that the total flavonoids before purification showed irregular sheet and massive structure,mass gathering and wrapped by membrane structure;the purified total flavonoids were no longer aggregated and wrappedby membrane structure,showing small irregular block and granular structure.4.In order to improve the application range of Astragalus total flavonoids in food,the paper analyzed the stability of total flavonoids,the results showed that it is soluble in polar solvents but not in nonpolar solvents and edible oil,and it is pale yellow in the different solvents,and the aqueous solution is weakly acidic.Temperature,p H,metal ions,food additives and redox agents have no significant effects on the stability of Astragalus total flavonoids,so it has good stability and can be used as natural food additives in food products.5.Based on the above test results,this paper studied the the preservation effect of Astragalus total flavonoids in apple juice,the results show that Astragalus total flavonoids can inhibit the activity of polyphenols oxidase in apple juice,delay the decline rate of total phenol and Vc content in apple juice,inhibit apple juice browning.