Preparation And Characterization Of Ultrasound-modified Chickpea Protein Isolate-ginseng Saponin Stabilized Antarctic Krill Oil Nanoemulsions

Antarctic krill oil（AKO）has attracted more and more attention due to its nutritional and functional potential.It has many functional properties,such as the treatment of dyslipidemia,chronic inflammation and cardiovascular diseases.The purpose of this project was to improve the solubility and oxidation stability of AKO by using the CPI-GS complexes modified by ultrasound.Besides,the in vitro digestion of emulsions stabilized by CPI-GS complexes was study,so as to expand the application of AKO in food industry.The main research contents listed as follows:Firstly,the effects of different ultrasound time（5,10,15,10,25 min）on the properties of CPI and CPI-GS complexes were investigated.After ultrasound pretreatment,the particle size and zeta potential of CPI decreased.The structure of protein molecule partially expanded and more non-polar groups were exposed,causng the surface hydrophobicity increased.Fluorescence spectrum analysis confirmed that ultrasound enhanced the interaction between CPI and GS.Circular dichroism spectra demonstrated that the addition of GS increased theα-helix content by 11.20%and reduced theβ-sheet,β-turn and random coil content by 3.70%,1.30%and 6.00%,respectively.After 15 min of ultrasound,the content of saponin at the interface increased significantly from 31.75%to 44.10%,while the content of protein at the interface decreased slightly.The antioxidant activity of U15-GS was the highest that DPPH radical scavenging activity was 2885.30μmol TE/L,ABTS radical scavenging activity was297.33μmol TE/L,total reducing activity was 51.42μmol TE/L,Fe²⁺chelating activity was82.09μmol TE/L,respectively.Secondly,the effects of ultrasound treatment of 15 min protein（U15）and different concentrations of（0.25%～4.00%）ginsenoside（GS）complexes on the properties of Antarctic krill oil nanoemulsions were investigated.In addition,the concentration of GS was optimized through the particle size,zeta potential,and physical stability of emulsions stabilized by CPI-GS complexes.The results showed that the optimal concentration of GS was 0.5%.Under these conditions,the particle size and the zeta potential of the U15-0.5%GS complex stabilized emulsions was 221.36±5.49 nm and-28.96±3.36 m V,which showed smaller particle size and more uniform particle size distribution than the U15 stabilized emulsion.Furthermore,the effects of different ultrasonic time（5～25 min）on the emulsion properties of CPI-GS complex were discussed.After ultrasonic treatment,the emulsion properties of CPI-GS complex changed significantly.Compared with the U0-GS complex,the TSI values of the emulsion formed by the U15-GS complex decreased from 7.76 to 2.54,indicating that the physical stability of the emulsion was improved after ultrasound pretreatment.In addition,the emulsions formed by U15-GS complex at p H 4 or 500 mmol/L concentration was not stratified,and the particle size of the emulsion did not change significantly.After 24 d accelerated storage test,compared with the emulsion formed by U0-GS complex,the PV values of the emulsion formed by the U15-GS complex decreased from 232.01 to 130.30 mg/L,the TBARS values decreased from 16.20 to 7.39 mg/L,and the retention rate of astaxanthin increased from 19.40%to 51.79%.It showed that reasonable ultrasound time could improve the environmental stability and oxidation stability of the emulsions formed by the CPI-GS complex.Finally,in vitro digestion model was adopted to investigate the digestion characteristics of AKO nanoemulsions formed by CPI-GS complexes that under different ultrasonic conditions.The ultrasonic treatment time had no significant effect on the particle size and potential of the emulsion after oral digestion.Emulsions formed by CPI-GS complex with ultrasonic time of 15 min or 20 min showed higher stability in simulated gastric（SGF）and simulated intestinal（SIF）than other emulsions.In SGF,The free fatty acid release rate and astaxanthin bioavailability of the emulsions formed by U15-GS complex were the highest（76.80%and 51.16%）.