Preparation And Functional Properties Of Buckwheat Protein Product

Buckwheat protein product(BWP) was prepared from buckwheat flour by method including alkaline extraction and isoelectric precipatation. Further studies were conducted to investigate the functional properties of BWP. BWP was indicated a potential source of functional dietary protein for possible application as ingredient in food industry.Buckwheat flour was suspended in certain buffer to form a mixture which was adjusted to optimum condition:pH8.00,tempreture50℃,span30min,s/lratio1:15,the protein extraction rate from buckwheat protein was 69.29%. The resulting slurry was separated into the supernatant and residue by a contimuous centrifuge(4000rpm for 5min).The pH of the supernatant was adjusted to pI3.80 by the addition of 10% HCl to precipate the protein isoelectically. Another continuous centrifuge (2000rpm for 5min) recovered most of the isoelectric precipitates formed,which accounts 73.80% of the total protein in the supernatant. After a washing with distilled water asjusted to pH3.80 by the addition of 10%HCl,the isoelectic precipitates were dissolved with distilled water and neutralized by the addition of 10%NaOH. Spray Drying and Vacuum Freezing & Drying were adopted to dehydrate the resulting solution whose protein concentration was about 10%.The comprehensive recovery of BWP was 63%.The chemical composition of BWP was as follows(%,w/w):water6.54,ash4.67,crud protein69.02,lipids15.24,starch2.76. The protein concentration of BWP was increased 5-6 fold compared with that of buckwheat flour ,while SDS-PAGE electrophoresis proved that the protein composition (subunit) of BWP not very different from that of buckwheat flour.The protein solubility(PS) of BWP was much greater than that of SPI. The isoelectric point(pI) of BWP was found around pH3.80,where the PS of BWP was minimum,max values of BWP was attained at pH levels far from pI. Heat or cold treatment did not cause much loss of solubility. Addition of NaCl or sucrose decreased the PS of BWP. BWP had a similar emulsifying property profile in comparison to SPI. Both emulsion capacity (EC) values and emulsion stability (ES) values of BWP were lower than those of egg white protein. The critical micellar concentrations(CMC) of BWP was disgovered at 0.8%(Pr.%, w/v), At all conditions, the BWP protein dispersion(0.5%, w/v) formed a rather thin foam, while egg white protein suspensions created a thick and sustained foam.