| Oysters are the most abundant shellfish in China,which are rich in protein.But functional properties of native oyster protein are not good and can't meet demands of food industry,so it has not yet been widely used in food industry.Besides,oyster protein denatures easily during processing caused decline of functional properties of oyster protein,which limits application of oyster protein in food industry.In this study,high pressure homogenization and ultrasound were used to treat the oyster protein to get the modified oyster protein with good functional properties which can meet the demands of food industry.The research contents and results are shown below:High pressure homogenization(HPH)was used to treat oyster protein suspention(10mg/mL)at different pressure(0,20,40,60,80,100 MPa)for three cycles.Changes of particle size,zeta potential,structure and functional properties of oyster protein were investigated after HPH.The study found that the particle size of oyster protein decreased significantly from 200-500 to 0-200 nm after HPH;the absolute zeta potential increased significantly(P?0.05)from12.67 to 33.57 mV.There was no obvious change of primary structure while significant change of high-level structure of oyster protein after HPH.Secondary structure of oyster protein after HPH was changed.Contents of?-helix decreased significantly from 48.3%to 30.4%while contents of?-turn(9.8%-21.0%)and random coil(18.4%-25.4%)increased significantly(P?0.05).Both free sulfhydryl(0.85-1.11?mol/g)and surface hydrophobicity(106.56-183.17?g)of oyster protein increased significantly(P?0.05)after HPH,which indicated changes in tertiary and quaternary structures.Functional properties of oyster protein are improved significantly(P?0.05)after HPH.Solubility increased significantly from 20.2 to 57.8%.OHC(981.8%-1290.4%),FA(17.5%-35.0%)and FS(44.7%-66.6%),EAI(8.87-17.06 m~2/g)and ESI(14.65-41.68 min)all increased significantly;while WHC decreased significantly(341.5%-217.0%).These results showed that HPH treatment made particle size decreased,partial structure unfolded,inside hydrophobicity groups exposed,which caused improvement of functional properties of oyster protein after HPHUltrasound was used to process oyster protein suspention(10 mg/mL)at different conditions(200 W 15 min;200 W 30 min;400 W 15 min;400 W 30 min;600 W 15 min;600W 30 min).Changes of particle size,zeta potential,structure and functional properties were investigated after sonification.As research showed,particle size decreased obviously after ultrasonic treatment,while absolute zeta potential increased significantly(P?0.05)from 7.93to 23.00 mV.Ultrasound had no distinct effect on primary structure of oyster protein,but had obvious effect on high-level structure.For its secondary structure,contents of?-helix decreased significantly from 57.6%to 35.5%while contents of random coil increased simultaneously from 13.1%to 32.1%(P?0.05).Both free sulfhydryl(3.61-8.06?mol/g)and surface hydrophobicity(663.16-1174.74)increased significantly but intrinsic fluorescence intensity decreased at maximum emission peak distinctly after ultrasound.All of them indicated changes of tertiary and quaternary structures of oyster protein after ultrasound.Solubility of oyster protein increased significantly from 16.6%to 99.1%after sonification;OHC(636.3%-934.67%),FA(12.3%-23.7%)and FS(69.8%-86.7%)as well as EAI(5.84-21.07 m~2/g)and ESI(11.44-17.65 min)all increased significantly(P?0.05)while WHC decreased significantly from 37.0%to 14.4%(P?0.05).Above results showed that particle size decreased,partial structure unfolded and inside hydrophobicity groups exposed after ultrasonic treatment which resulted in improvement of functional properties of oyster protein after ultrasonic treatment. |
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