Study On The Extraction And Application Of Finger Millet Bran Polyphenols

In order to further develop and utilize the Finger millet resources,improve the comprehensive utilization of Finger millet by-products in our country and the added value of Finger millet,this study used Finger millet bran as raw material to optimize the optimal extraction process for Finger millet bran polyphenols（FMBP）,and analyze the biological activity of FMBP.This study also explored the inhibitory effect and mechanism of FMBP on the formation of advanced glycation end products（AGEs）,as well as its application in active packaging films.（1）Using the Finger millet bran as raw material and the productivity of polyphenols as the evaluation index,through single factor test and response surface optimization analysis,the optimal process conditions were determined as follows:the solvent was 63%ethanol solution,the liquid-to-material ratio was 73:1（m L/g）,the extraction time was 46 min,and the extraction power and extraction temperature were fixed in this experiment,at 40k Hz,500W and 50℃,respectively.The productivity of FMBP under these conditions was（7.183±0.104）mg/g.The result was close to the optimized prediction value of 7.199 mg/g by response surface.So,the results of response surface were accurate and reliable.（2）The ethanolic extract of the Finger millet bran was characterized by ultraviolet and infrared spectra,and the ethanolic extract of the Finger millet bran was preliminarily determined to be polyphenols.The antioxidant activity of the FMBP was further evaluated by reducing ability,₂^-·scavenging ability,·OH scavenging ability and DPPH·scavenging ability.At the same time,the antibacterial activities against Escherichia coli,Staphylococcus aureus,and antifungal activity against Penicillium nettle,Aspergillus fumigatus of FMBP were also analyzed.The results showed that FMBP had good antioxidant activity and antibacterial activity,and the antioxidant activity had a certain dose-dependence.（3）Model systems of bovine serum albumin（BSA）-glucose（Glucose）and fish sausage were established,which constituted two different systems that could form advanced glycation end products（AGEs）.Using different concentrations of FMBP as inhibitors,the effects of fluorescent AGEs,glucose,lysine,and sulfhydryl group content in the in vitro simulation system and fish sausage model were studied,as well as the influence on the relative molecular weight of proteins in the simulation system.The results showed that the FMBP had an inhibitory effect on fluorescent AGEs in the two established reaction systems,and the inhibitory effect was enhanced with the increase of the concentration of FMBP.The contents of glucose,lysine and sulfhydryl group were positively correlated with the concentration of FMBP.The results of gel electrophoresis showed that FMBP inhibited the cross-linking of protein and glucose.（4）The chitosan/gelatin-based films were prepared by incorporation of FMBP with different concentrations and their physico-chemical,antioxidant and antimicrobial activities were investigated.The results indicated the thickness was gradually increased,whereas the water content,water absorption light and transmittance at 600nm was significantly decreased with the addition amount of FMBP.The water vapor permeability of films was significantly decreased after incorporation of 0.25 and 0.50%of FMBP,whereas it was significantly increased after incorporation of 0.75 and 1.00%of FMBP.Loading with FMBP significantly enhanced the antioxidant activity,antibacterial activity against Escherichia coli and antifungal activity against Penicillium nettle.The FTIR revealed that strong interactions between FMBP and chitosan/gelatin matrix when 0.25 and 0.50%of FMBP were added into the films.Scanning electron microscopy analysis revealed that that the FMBP could incorporate into the chitosan/gelatin matrix well at an appropriate concentration that resulted in smooth and uniform surface.In summary,the addition of FMBP at an appropriate concentration（≤0.50%）could improve the physico-chemical properties,biological activities of the chitosan/gelatin films.