Characterization And Application Of Dissociation-Association Behavior Of Soy Lipophilic Protein

For the past few years,with the increasing awareness and attention of the relationship between food and health,the demands on novel functional food is increasing.Meanwhile,the encapsulation of hydrophobic bioactive substances with plant protein via self-assembly nanoparticles has attracted much attention.Soy lipophilic protein(SLP),is a soy protein component with obvious obvious hydrophobic and hydrophilic boundaries and rich in phospholipids,with the potential function of carrying hydrophosic active substances.Up to now,studies on SLP have been less reported and the construction of SLP nanoparticles and their complex formation have not been reported.On this basis,in this paper,taking SLP as object,the extraction,structure,and composition were studied.The dissociation-association behavior of SLP subunits was investigated during the construction process of SLP nanoparticles by acid induced and heat induced.The mechanism of interaction between Nano-SLP and curcumin(Cur)and the tructure and functional properties of nanoparticle complex were further studied.The main conclusions of this paper are as follows:(1)The highest yield of SLP was 11.8%gained by single-factor experiment and response surface.The best extraction parameters were as follows,extraction temperature 47?,extraction time 62 min,p H 8.5,and Tris-HCl concentration 0.05 M.The composition analysis showed that SLP was rich in branched chain amino acids(16.44 g/100 g)and containing 27 fatty acids.Compared with SPI,11S globulins,and 7S globulins,SLP possessed the maximum emulsification activity index(159.27 m~2/g),while the solubility was minimum(45%).In addition,in vitro antioxidant assay results showed that,SLP had well free radical scavenging effects and iron reduction force.(2)The dissociation and association behavior of SLP based on acid-induced treatment was characterized by the combination of multispectral and thermal analysis technology.The analysis results showing that,during the acid-induced treatment,the structure of SLP undergoes unfolding,subunit dissociation and re-aggregation,and the conformation was stabilized after induced by acid for about 8?10 hours,which made the surface of SLP to be distributed more tyrosine and tryptophan and a loose three-dimensional conformation,which eventually lead to the destruction of the hydrogen bonding of the secondary structure,resulting in a decrease in the content ofa-helix and an increase in the?-sheet content.The SLP particles induced by the offset treatment at p H 4 showed a relatively narrow normal distribution and the largest hydrodynamic radius.(3)Results showed that,the range of 80?90?was the boundary of SLP in the heating proceing.When the temperature is lower than 80?,the conformation of SLP could be basically maintain without significant changing.Significant changes occur in the secondary conformation of the SLP at a temperature higher than 90?.The SLP molecules gradually stretched,and depolymerized to form free subunits at 90?,along with an increase in?-sheet and random structure content and a decreasing content ofa-helix and?-turn content.The electrophoretic analysis shows that the dissociate subunits are reassembled into intermediate aggregates by hydrophobic interactions and disulfide,resulting in increased molecular aggregation and increased conformation stability.SLP are self-assembled to form a single-distribution stable nanoparticle system with a particle size of about 110 nm treated at 90?for 20 min.(4)Nano-SLP-Cur complex was constructed based on protein self-assembly nanotechnology by ultrasound treatment,which effectively improved the solubility and thermal stability of Cur.,as well as,the in vitro digestibility of SLP.The analysis of fluorescence dynamics shows that the type of fluorescence quenching of Nano-SLP interaction with Cur is static fluorescence quenching.Cur binds to the Nano-SLP surface in a non-stereotyped form by hydrogen bonds and van der Waal force,which significantly altering the Nano-SLP-Cur conformation,resulting in a significant reduction ina-helix andb-sheet content of the Nano-SLP-Cur,while theb-turn and random coil are significantly increased.In summary,as a new soy protein component,SLP has higher nutritional value and application potential.Regular shapes and uniform sizes of self-assembly Nano-SLP particles could be constructed via acid-induced combined with thermal treatment.The solubility and stability of Cur could be significantly improved by Nano-SLP-Cur particles,which could be used as a bioactive substance transportation carrier in food formulations.