Extraction Technology And Functional Characteristics Of Protein And Flavonoids In Germinated Foxtail Millet

Foxtail millet?setaria italica L.Beauv?is one of the main crops in China,and its nutritional composition is relatively complete.Germination can transform the nutrients in the seeds,and the active substances beneficial to the human body will increase,while the protein quality and functional properties can be effectively improved,and the anti-nutritional factors are reduced.In this experiment,the foxtail millet was used as raw material and germinated,and its index was determined to optimize the extraction process of germinated foxtail millet flavonoids and its protein.The changes in the functional properties of foxtail millet proteins in each germination period were analyzed.The purified granulated flavonoids were subjected to infrared and electron microscopy scanning,and the antioxidant capacity of germinated foxtail millet flavonoids before and after purification was determined.The results are as follows:1.The germination treatment of foxtail millet could visually express the morphological changes of samples in each period.This time,the foxtail millets germinated for 12 h,24 h,36 h,48 h,and 72 h was tested as samples.As the soaking time increased,the water absorption rate of the foxtail millet increased sharply and then tended to be flat,and then began to rise.The bud length of foxtail millet grew faster in 24⁶0 h,and grew slowly after 60 h.The content of ash and fat showed a decreasing trend with the increase of germination time.With the increase of germination time,the content of protein,flavonoids,total amino acid and essential amino acids in foxtail millet samples showed an upward trend.After 72 h of germination,the EAA/TAA value was 38.25%,and the EAA/NEAA value was61.94%,which was close to the ideal mode of FAO/WHO.2.Ultrasound-assisted extraction of protein and flavonoids from germinated 72 h foxtail millet was carried out.The single-factor and response surface tests were carried out to determine the optimum extraction conditions for the protein:material to liquid ratio 1:9?g/mL?,ultrasonic power 480 W,and ultrasonic time 30 min.The protein extraction rate of the germinated foxtail millet was 49.16%,which was very close to the predicted value.The optimal extraction conditions are obtained as follows:ethanol content,70%;material to liquid ratio,1:25?g/mL?;ultrasonic power,370 W;and ultrasonic time,28min.Under the optimized conditions,the content of flavonoid was 9.92 mg/g,which was very close to the predicted value.3.The relative content of?-fold structure of germinated 72h foxtail millet protein was significantly higher than that of germinated 48h sample,and the content was the highest,which was 43.08%.The relative content of irregular coil structure showed a downward trend with the increase of germinated time.The relative content of?-helical structure of ungerminated foxtail millet protein was the highest,which was 31.55%.The relative content of?-helical structure showed a upward trend during24⁴8 h germination,and decreased significantly after 48 h.The content of?-turn structure increased with the increase of germination time in 0⁴8h,and decreased after 48h.4.Germination could increase the solubility of foxtail millet protein.The solubility of foxtail millet protein decreased in the range of pH 2⁴,but it showed an increasing trend in the range of pH 4¹0.After 72 hours of germination,The water holding capacity of foxtail millet protein was 1.38 times that of ungerminated samples,and the oil holding capacity was 0.77 times.With the increase of germination time,the foaming ability of foxtail millet protein was improved,but its foaming stability shows a downward trend overall.When the pH was 10,the germinated 48 h foxtail millet protein showed the best foaming ability,which was 56.13%,but its foaming stability was the worst,which was 22.19%.When the pH was 4,the ungerminated foxtail millet had the lowest foaming capacity,which was 20.04%,but its foaming stability was the best,which was 69.97%.With the increase of germination time and pH,the emulsification activity of foxtail millet protein also increased.When the pH was 10,the emulsification activity of germinated 72 h foxtail millet protein was the highest,which was 76.05%,and the emulsion stability was relatively better.5.FTIR spectral scanning of the purified flavonoids of germinated foxtail millet was conducted.From the obtained spectrum,it could be seen that when the wave number was 3300.20,2926.01,2854.65,1379.79,1651.07,1556.59 cm^-1 and 1070cm^-11420 cm^-1,the absorption peak with a characteristic functional group of a flavonoid appeared.Microscopic analysis of the electron micrographs of the crude extracts of granulated flavonoids and purified substances showed that the number of flaky and granular granules increased significantly after purification by polyamide resin.The VC was used as a control to explore the scavenging ability to hydroxyl and DPPH radical before and after purification of flavonoids.The experimental results showed that when the mass concentration was 0.7 mg/mL,the scavenging ability of germinated millenium flavonoids to hydroxyl radicals was better,which was 78.35%,and the scavenging ability to DPPH free radicals was the second,which was 72.89%.