Studies On The Structure And Functional Properties Of Ultrasonic Treated Water Soluble Protein From Moringa Oleifera Seeds

Moringa Oleifera seeds protein has excellent functional properties.Modification can further improve its functional properties and increase its development and utilization prospects.This paper was aim to study the structure and functional properties of ultrasonic treated water soluble protein from degrease Moringa Oleifera seeds(MOWP)and its corresponding mechanism.Meanwhile,effects of p H value on conformational and functional properties of ultrasonic pretreatment MOWP were researched;finally influences of inulin on the emulsion properties of ultrasonic treated MOWP.The main results are as follows:1.FTIR and Raman spectroscopy analysis showed that MOWP was mainly composed of β-sheets and β-turns,and the content of β-sheets and β-turns were significantly reduced after ultrasonic treatment.And the ultrasonic treatment with 60% power(390W)had the most significant effect with the secondary structure of MOWP.Scanning electron microscope(SEM)analysis demonstrated that MOWP was mainly loose and irregular small particles,and ultrasonic treatment made the protein st ructure more compact.SDS-PAGE showed that MOWP intermolecular aggregation resulted in the formation of large molecular weight subunits,but it did not significantly change the small molecular weight subunits.At the same time,the thermal stability index of MOWP was shifted to a high temperature and up to 81.70℃.2.In the acidic environment,the extent of intermolecular aggregation MOWP treated by ultrasound was enhanced,and the extremely acidic environment promoted the denaturation of MOWP and the formation of small-size polypeptide polymers.In alkaline environment,the irregular curl of MOWP was increased,and the degree of fluorophore exposure was increased.The fluorophore exposure site and the tertiary structure was changed by ultrasonic treatment.The particle size,charge and surface hydrophobicity of MOWP were significantly reduced by ultrasonic treatment with 40% and 60%power.At p H 3 the MOWP with ultrasonic treatment showed the highest solubility and foaming ability.The ultrasonic treatment with high power(80%and 100%,520 W and 650W)would significantly enhance the solubility and foaming ability of MOWP.At the alkaline solution environment,the MOWP emulsification index and emulsification stability was enhanced,and the emulsification index of MOWP treated by ultrasound with 60% power was298.16 ± 5.07 mg/m L when the p H was 11.3.With the increase of ultrasonic pretreatment power,MOWP digestibility was firstly decreased and then increased.Endogenous fluorescence spectrum analysis showed that ultrasonic treatment could change the binding mode and tertiary structure of the polypeptides in MOWP,and increase the molecular weight of the enzyme-cutting polypeptide chain.Ultrasonic treatment could improve the antioxidant activity of gastrointestinal digestive products of MOWP.4.The addition of inulin could significantly improve the emulsifying effect of MOWP and inhance the storage stability of emulsion.The emulsifying ability of MOWP pretreated with 60% power ultrasonic(MOWP-60)was better than that of MOWP,in which 1wt % and 3wt % inulin could significantly improve the emulsifying index and interfacial adsorption protein content of MOWP-60.SDS-PAGE showed that the emulsification was mainly performed by 20.0 k Da and 32.0 k Da subunits.MOWP-60 emulsion had the best stability effect by adding 3wt % inulin.