Extraction Of Flavonoids From Buckwheat Bran And Preparation And Application Of Chitosan Composite Membrane

Buckwheat(Fagopyrum esculentum moench)is an annual herbaceous plant,which is commonly divided into common buckwheat(sweet buckwheat)and tartary buckwheat(tartary buckwheat).The byproduct of buckwheat flour during processing,buckwheat bran,is often used as feed or directly discarded due to its poor taste and difficulty in digestion and absorption by the human body,resulting in waste and environmental pollution.However,it contains various active ingredients such as flavonoids and dietary fiber,which are highly valuable for development.This study used buckwheat bran as raw material to optimize the extraction of buckwheat bran flavonoids(BBF),and studied its structure Determination and analysis of stability and antioxidant activity;chitosan(CS)was used as the filmforming substrate and different concentrations of BBF were added to prepare buckwheat bran flavonoid chitosan(BBF-CS)composite films.The physicochemical,functional,and structural properties of the films were studied and applied to edible oil storage.The main research is as follows:(1)This study used buckwheat bran as the raw material and used ultrasound assisted extraction of BBF for process optimization.The structure of flavonoids was characterized by color reaction,Fourier transform infrared spectroscopy(FT-IR),and scanning electron microscopy(SEM).The results showed that the optimal extraction process for BBF was as follows:the ratio of material to liquid was 1:50,the volume fraction of ethanol was 50%,the ultrasound temperature was 70℃,and the ultrasound time was 80 min.Under this process,the content of flavonoids extracted and purified was 36.25%.Combining color reaction,FT-IR,and SEM analysis,it was found that the extract reacted with certain metal ions to form a specific colored complex.There were multiple characteristic absorption peaks in the infrared spectrum.SEM showed that the extract was powdery and granular,with multiple layers of microstructure.The results showed that the extract was a flavonoid compound.(2)The stability and antioxidant activity of BBF were measured and analyzed.The experimental results show that BBF is not suitable for storage in an acidic or alkaline environment,and flavonoids are most stable at pH 5 to 7;There was no significant change in flavonoids content at room temperature,and flavonoids were the most stable at 4℃;BBF should be stored away from light and avoid contact with Ca2+,Fe3+,and Cu2+.The results of antioxidant activity measurement in vitro showed that BBF had a high scavenging capacity for superoxide anion,DPPH,and ABTS+free radicals,with a maximum scavenging rate of 89.41%,98.7%,and 98.84%,respectively,and a reduction power absorbance value of 3.95 for iron ions;The scavenging ability of BBF on superoxide anion,DPPH,and ABTS+free radicals was significant,with the maximum scavenging rates of 53.81%,92.1%,and 87.7%,respectively.The absorbance value of BBF for iron ions reached 3.54.The results show that BBF has strong antioxidant properties in vitro and has great potential for development as a natural antioxidant.(3)Using CS as the film forming substrate,adding different concentrations of BBF to prepare composite films,and measuring their physical and chemical properties(such as thickness,transparency,color,moisture content,solubility,tensile strength,and elongation at break);And determine the antioxidant activity of the composite membrane;The composite films were characterized by FT-IR,Xray diffraction,particle size,Zeta potential,and SEM;The value of composite film in edible oil storage and preservation was analyzed by acid value and peroxide value.The results show that compared with CS films,BBF-CS composite films have higher thickness,opacity,and yellowness values,while L*values,total color difference,water content,solubility,tensile strength,and elongation at break are lower;The antioxidant activity of the composite membrane was significantly increased in DPPH free radical scavenging ability,ABTS+ free radical scavenging ability,superoxide anion free radical scavenging ability,and total reduction ability(P<0.05);The BBF-CS composite film shows a characteristic absorption peak,and the film shows scattered white spots,with a rough and uneven surface;The acid value and peroxide value of the composite film are lower than those of the shell CS film during storage.It provides a reference for the preparation and application of BBF-CS with bioactive substances added.