Study On Improving Gelation Of Peanut Protein By Ultrasonic And Enzyme Cross-linking

China has abundant peanut resources,and most of them are currently used for oil production.The peanut protein in the cake obtained by the traditional oil production method is severely denatured and difficult to be extracted and utilized,resulting in a great waste of peanut protein resources.The natural peanut protein has poor gelability,which limits its application in the food industry.By modifying the natural peanut protein to a certain extent,its gel properties can be improved.In this project,the peanut oil and protein were simultaneously extracted by the aqueous solution method.First,the influence of environmental factors（pH,ionic strength,and surfactant）on the gelatinity of peanut protein was studied.Second,the peanut protein was subjected to high field under different pH conditions.Strong ultrasonic treatment to analyze the effect of pH and ultrasonic treatment on the structure and gelability of peanut protein;then use ultrasonic wave to synthesize modified glutaminase to modify peanut protein to study the effect of composite modification on peanut protein structure and gelability,And apply the modified peanut protein to sausage processing.The research results are as follows:pH has a significant effect on the gelatin and structural properties of peanut protein.Peanut protein gel has the largest gel strength,water holding capacity and storage modulus（G′）at pH3;in the neutral and alkaline range,peanut protein gel has the highest strength,water holding capacity and G′value at pH8.Hydrophobic interactions play the most important role in the formation of peanut protein gels,followed by disulfide bonds.Peanut protein has the highest surface hydrophobicity and free thiol content at pH3,and the endogenous fluorescence spectrum has a clear red shift;while in the neutral and alkaline ranges,the surface of peanut protein（after heating）at pH8 is the most hydrophobic and free The sulfhydryl content is high.As the content of Tween 20 increases,the gel hardness of peanut protein decreases and the surface hydrophobicity decreases.Compared with peanut protein,the endogenous fluorescence spectrum of each sample containing Tween has a blue shift.The addition of Ca Cl₂ contributes to the formation of the gel,and as the ion concentration increases,the gel hardness gradually increases,and the water retention also increases;within a certain concentration range,the addition of Na Cl can also make peanut protein gel The hardness and water holding capacity are increased.Ultrasonic treatment at different pH values has a significant effect on the structure and gel properties of peanut protein.Peanut protein was sonicated at pH 8（15%protein concentration）,and peanut protein subunits were significantly degraded by SDS-PAGE experiments,and gel filtration chromatography showed that peanut protein molecules had re-aggregation behavior;at pH 3 Sonication of peanut protein solutions at the same concentration did not reveal degradation of the subunits,but peanut protein molecules depolymerized and the molecular weight decreased.With ultrasonic treatment at different pH,the surface hydrophobicity and exposed free sulfhydryl content of peanut protein both increased first and then decreased with the increase of ultrasonic power,and reached the highest when the ultrasonic power was 200W.Ultrasonic treatment under both acid and alkali conditions reduced the fluorescence intensity of peanut protein and increased the UV absorption intensity.By measuring the secondary structure,it can be seen that after ultrasonic treatment at pH3,the content ofα-helix and random curl of peanut protein showed an increasing trend,and the content ofβ-fold andβ-turn angle showed a downward trend;after ultrasonic treatment at pH8 The content ofα-helix andβ-sheet of peanut protein showed a downward trend,the content of irregular curl showed an increasing trend,and the content ofβ-turn did not change significantly.At pH 3,the gelatin properties of peanut protein were reduced by ultrasonic treatment,while at pH 8,the gel properties were improved by ultrasonic treatment.The dynamic rheological test results show that the G’value of the sonicated gel at pH 3 is lower than that of the unsonicated sample,while at pH 8,the sonicated sample has the largest G’value at 200W.It can be seen from the scanning electron micrograph:under the condition of pH3,the greater the ultrasonic power,the looser the microstructure of the gel,while under the condition of pH8,the greater the ultrasonic power,the microstructure of the gel changes from regular pores to no regular lamellar structure.Ultrasonic treatment has no obvious effect on the change of free amino content of peanut protein,and the cross-linking of ultrasound and TG enzyme significantly reduces the free amino content of peanut protein,and the minimum free amino content of ultrasonic power is 200W,indicating that the enzyme crossover The highest degree of joint reaction.Compound modified peanut protein samples have new subunit bands with larger molecular weight at the top of the electropherogram.Ultrasound and TG enzyme cross-linking increased the surface hydrophobicity and free thiol content of peanut protein first,and then showed a downward trend.Compared with the ultrasonic treatment alone,the surface of the composite modified sample decreased in hydrophobicity and the content of free thiol groups increased.From the analysis of circular dichroism,it can be seen that with the increase of ultrasonic power,the content ofα-helix andβ-turn structure gradually decreases,and the content ofβ-sheet and random curl structure increases.Ultrasound and TG enzyme cross-linking can improve the gel hardness and water holding capacity of peanut protein gel,and when the ultrasonic power is 200W,the compound modified peanut protein gel has the highest gel hardness and water holding capacity.From the microstructure,it can be seen that the unmodified peanut protein gel has a large and irregular pore network structure,while the peanut protein gel cross-linked by ultrasound and TG enzyme has smaller pores and is more evenly distributed.It can be seen from the sausage texture characteristic index that the sausage gel made by soy protein has the highest hardness,followed by the compound modified peanut protein and unmodified peanut protein,and the sausage made by modified peanut protein has better elasticity than soybean protein and unsettled.Sausage made from modified peanut protein.