Research On Structural Characterization And Functional Properties Of Pleurotus Eryngii Protein

[Objective] In order to develop the deep processing products of Pleurotus eryngii protein,it is necessary to research the changes of structural characterization and functional properties of Pleurotus eryngii protein during processing.Therefore,this experiment mainly researched the effects of different treatments on the structural characterization and functional properties of Pleurotus eryngii protein to provide a theoretical basis for processing.[Method] The Pleurotus eryngii protein was selected as the research object.The physical and chemical properties of Pleurotus eryngii protein were studied by heat treatment,ultrasonic treatment and deamidation modification,including hydrophobicity,sulfhydryl content,secondary structure and holding properties,oil holding properties,foaming and foaming stability properties,emulsifying and emulsifying stability properties,digestibility properties and rheological properties.[Results]?1?The secondary structure of Pleurotus eryngii protein was changed to some extent by different heat treatment,ultrasonic treatment and deamidation modification.The untreated Pleurotus eryngii protein total thiols,free sulfhydryl and disulfide bond contents were 20.7 ?mol/g,11.0 ?mol/g and 48.0 ?mol/g.The content of ?-helix,?-sheet,?-turn and random curl were 12.88%,43.30%,21.74% and 22.08%,respectively.After heat treatment and ultrasonic treatment the fluorescence intensity of Pleurotus eryngii protein increased,the hydrophobicity increased,the sulfhydryl content decreased.The solubility and oil holding capacity of Pleurotus eryngii protein were relatively high and the absorption peak of infrared spectrum did not change,but the absorption intensity increased.At the same time,the functional properties test results showed that the SA,WA,OA,ESI,FC and FS of Pleurotus eryngii protein increased first and then decreased at the same temperature.The solubility,WA,OA,EAI and ESI,FC and FS increased with the temperature increasing.At the same ultrasonic frequency,the WA and OA of Pleurotus eryngii protein increased,SA,FC and FS,EAI and ESI increased first and then decreased with the prolongation of ultrasonic time.With ultrasonic frequency large increasing,the SA,WA,OA,FC,EAI showed an increasing trend,FS decreased first and then increased,ESI increased first and then decreased.?2?Rheological test results showed that the protein concentration,pH and Ca²⁺ concentration had a significant effective on the rheology of Pleurotus eryngii protein.With protein concentration increasing,the apparent viscosity of Pleurotus eryngii protein was higher,and the hysteresis was more obvious.With the temperature increasing,the apparent viscosity of the solution was lower under the same protein concentration.As the shearing force increaseing,the Pleurotus eryngii protein had higher apparent viscosity and the hysteresis area was more obvious.With the temperature increasing,the apparent viscosity decreased under the same p H condition.The shear stress of the solution increased with the shear force increasing.As increasing of Ca²⁺ concentration,the apparent viscosity of Pleurotus eryngii protein was higher.The shear stress of the solution increased with the shear force increasing.All experiments showed that the Pleurotus eryngii protein was pseudoplastic fluid.?3?In this experiment,using the response surface optimization design test,the optimum conditions of the acid deamidation of Pleurotus eryngii protein was hydrochloric acid concentration 0.175 mol/L,treatment temperature 57.5 °C,treatment time 121 min 5 s.On this condition,DAD value of the protein was 71.92%.The effect of acid deamidation on the functional properties of Pleurotus eryngii protein showed that the deamidation modification could improve the solubility,oil-holding,foaming and emulsifying of Pleurotus eryngii protein,but the improvement of water-holding was not obvious.The results of the digestive test showed that the heat treatment,ultrasonic treatment and acid deamidation treatment increased the digestibility of Pleurotus eryngii protein,improved the antioxidant activity and the intestinal absorption capacity.[Conclusion] Different heat treatment and ultrasonic treatment could change the secondary structure of Pleurotus eryngii protein.And the solubility?SA?,water holding capacity?WA?,oil holding capacity?OA?and foaming?FA?,foaming stability?FS?,emulsifying?EAI?and emulsion stability?ESI?of Pleurotus eryngii protein increased.Pleurotus eryngii protein concentration,p H and Ca²⁺ concentration had a significant effect on rheology properties.In addition,Pleurotus eryngii protein solution was pseudoplastic fluid.Heat treatment,ultrasonic treatment and deamidation increased the digestibility of Pleurotus eryngii protein and enhanced the antioxidant activity and intestinal absorption capacity of digestive juice.