Effects Of Processing Technology On Extraction Rate And Characteristics Of Soybean Milk Protein

Soybean protein belongs to amphoteric substance,has low natural resource cost and excellent functional properties,which increases people’s interest in soybean protein as a nutrient and functional component in food machining.The aim of this paper is to enhance protein dissolution rate in soymilk and lessen residue in bean dregs,the paper researched the effects of diverse methods(（ultrasonic,microwave and steam flash explosion treatment）on extraction rate of soymilk and residue rate in soybean dregs,as well as functional features of soy protein.The text results of soymilk protein dissolution rate indicated that extraction rate of soymilk protein was increased observably after 0.2%（w/v）NaHCO₃machining,which was 75.86%.After ultrasonic treatment,when the ultrasonic conditions were 800 W and 40 min,the highest extraction rate of soybean milk protein was 82.79%.After microwave treatment,the microwave factors of highest protein dissolution rate in soymilk were 700 W and 90 s,extraction rate was 80.98%.After steam explosion treatment,when the steam explosion conditions were 0.3 MPa and 90 s,the maximum extraction rate of soymilk protein was 80.01%.The results of NMR revealed that water absorption capability of soybean cotyledons increased significantly after different processing methods.After ultrasonic treatment,the water absorption effect is the most significant.The relaxation time of steam flash explosion treatment shifted to the right obviously.T₂₂component is most significantly affected by different handling methods.The results of scanning electron microscope of soybean dregs showed that the cell structure of untreated soybean residue is compact,and the structure of treated soybean residue is gradually loose and porous.After ultrasonic treatment,soybean residue is most seriously damaged and almost completely broken.The experimental results of stability coefficient and sedimentation rate of soybean milk showed that the stability coefficient of soybean milk after NaHCO₃and ultrasonic treatment increased to 0.857 and 0.839 respectively,and the sedimentation rate decreased to 0.929 and 1.118respectively;The stability coefficient of soybean milk after microwave and steam flash explosion treatment decreased,which were 0.772 and 0.608 respectively;The sedimentation rate increased to2.776 and 1.605 respectively.The results of soybean milk color difference experiment showed that the a^*and b^*values of soybean milk after steam flash explosion treatment were the largest,which were 0.48 and 11.50 respectively,indicating that the color of soybean milk after steam flash explosion treatment was yellow and dark;After NaHCO₃,ultrasonic and microwave treatment,a^*and b^*reduced,and the color and lustre of soymilk was bright.The outcomes of structure of soymilk protein considered that particle diameter decreased after NaHCO₃and ultrasonic process at 800 W and 40 min,which were 150.56 nm and 123.50 nm respectively.After microwave and steam flash explosion treatment,the particle size of soybean milk protein increased,which were194.5 nm and 265.23 nm respectively.The turbidity of soybean milk protein after ultrasonic treatment was the lowest,0.258,lower than 0.522 in the control group.The turbidity of soybean milk protein after steam flash explosion of 0.3 MPa and 90 s was the highest,0.894,higher than0.114 in the control group.The protein solubility increased after NaHCO₃treatment and ultrasonic treatment at 800 W and 40 min,which were 86.79%and 88.43%respectively;The protein solubility decreased after microwave and steam flash explosion treatment,which were 84.32%and83.54%respectively.After NaHCO₃,ultrasonic,microwave and steam flash explosion treatment,α-Spiral,β-the content of corner and irregular curl increases significantly,β-the content of folded structure decreased,indicating that after NaHCO₃,ultrasonic,microwave and steam flash explosion treatment,β-the folded structure is partially transformed intoα-spiral,β-corner and irregular curl structure.The fluorescence intensity of soybean milk protein treated with NaHCO₃,ultrasound,microwave and steam flash explosion improved evidently.The hydrophobicity of soymilk protein abated after NaHCO₃and ultrasonic process,which were 646.35 and 554.80respectively;The surface hydrophobicity of soybean milk protein increased after microwave and steam flash explosion treatment,which were 817.80 and 1111.90 respectively.After NaHCO₃and ultrasonic treatment,the content of free sulfhydryl of soymilk protein ascended remarkably and the content of disulfide bond decreased strikingly.In contrast of NaHCO₃and ultrasonic treatment,the content of free sulfhydryl and disulfide bond were opposite.According to the experimental results of functional properties of soybean protein,the water grasping ability of soymilk protein debased by 0.5,3.3,8.4 and 8.1 g/g respectively after NaHCO₃,ultrasonic,microwave and steam flash explosion treatment.The oil holding capacity of soybean milk protein increased after NaHCO₃,ultrasonic,microwave and steam flash explosion,but the difference was not significant.The oil holding capacity of soybean milk protein treated by steam flash explosion was the highest,which was 3.68 g/g,which was 11.01%higher than the matched group.The foaming ability（32%）and foaming stability（75%）of soymilk protein after ultrasonic treatment were markedly higher than control group.The foaming ability of soybean milk protein treated with NaHCO₃,microwave and steam flash explosion was higher than that of the control group,22%,30%and 28%respectively.The foaming stability of soybean milk protein treated with NaHCO₃,microwave and steam flash explosion was 72.73%,75%,60%and 64.29%respectively.The emulsifying properties of soybean milk protein after NaHCO₃and ultrasonic treatment was31.32 m²/g and 30.89 m²/g respectively,which was slightly higher than that of the control group;The emulsifying activity of soybean milk protein after microwave treatment was 20.63 m²/g,and that after steam flash explosion treatment was 39.06 m²/g.The change trend of emulsifying stability is not exactly the same as that of emulsifying activity.The emulsifying stability of soymilk protein ascended obviously after ultrasonic process,which was 25.15 min.The emulsifying stability of soybean milk protein after NaHCO₃and microwave treatment was the opposite,22.18 min and 24 min respectively;The emulsifying stability of soybean milk protein after steam flash explosion treatment was 27.34 min.