Preparation And Modification Of Tartary Buckwheat Bran Protein And Its Application In Nano-emulsion

Tartary buckwheat is an important resource of medicines and foods.Tartary buckwheat bran is the by-product of tartary buckwheat processing.Its development and utilization are rarely reported,which results in a great waste.In view of this,this project intends to isolate tartary buckwheat bran protein(TBBP),investigate the functional properties of TBBP,and systematically study the interaction mechanism between TBBP and flavonoids.On this basis,TBBP-rutin complexes were constructed.Moreover,the nano-emulsion containing ?-carotene was constructed with the TBBP-rutin covalent complex as emulsifiers,the properties of nano-emulsion were investigated.The main results are as follows:Tartary buckwheat bran accounted for 15.33% of the total weight of tartary buckwheat,which was rich in protein,oil and cellulose.Tartary buckwheat bran had great development value for its high protein content(36.51%)and reasonable amino acid composition.TBBP was mainly composed of soluble proteins(albumin and globulin),which accounted for 44.32% of the total protein.TBBP was rich in the essential amino acids and the limiting amino acid in grains(lysine).The p H isoelectric point of TBBP was 4.5,and the solubility of TBBP showed a typical U-shaped curve with p H.The solubility,water holding capacity,oil holding capacity and foaming of TBBP were lower than SPI,while its emulsifying capacity was higher than SPI.The interaction between 21 kinds of flavonoids with TBBP were studied by fluorescence spectrometry.It was found that rutin,as the representative of flavonoid glycosides,had the strongest binding ability to TBBP.The thermodynamic analysis showed that the binding was a spontaneous process driven by hydrogen bond and van der Waals force.In this process,the hydrophobic microenvironment of TBBP tryptophan increased,while the microenvironment of tyrosine remained unchanged.Compared with TBBP,the solubility and antioxidant capacity of covalent and noncovalent complexes of TBBP-rutin were improved.The ?-carotene nano-emulsion stabilized by TBBP,TBBP-rutin covalent and noncovalent complexes were prepared,and their droplet sizes,Zata potentials,polydispersity coefficients(PDI)were also determined,the retention and stability of ?-carotene of these nano-emulsions were compared.The results showed that TBBP-rutin covalent complex has the strongest emulsifying ability,which was attributed to its higher interfacial protein and rutin content.The initial droplet size of nano-emulsion developed by TBBP-rutin covalent composite was 243.4 nm,Zata potential was-32.7 m V,PDI was0.275,and the droplet size and Zata potential had no significant change within 28 days,which could be regarded as completely stable nano-emulsion.The loading rate of ?-carotene reached 92% in this nano-emulsion,and it had good stability under light at 30 ?,and in darkness at 25 ? or 37 ?.However,fading was found when stored at 55 ? for 4weeks.The short high temperature had less effect on the droplet size of this nanoemulsion,nevertheless,it was sensitive to salt ions.