Modiifcation Of Cottonseed Protein Based On Physical Methods

Using cottonseed meal as raw material, alcohol and alkali as extraction agents, thisresearch systematically studied the extraction and the functional properties of cottonseedprotein. Three physical modified methods including heating, ultrasonic and microwave wereused to improve the solubility and other functional properties.Cottonseed proteins were prepared via ethanol and hot alkali extraction and therecovery rates were compared. With60%ethanol extraction,71.01%content of protein wasobtained; at the same time, the protein yield was46.73%and gossypol content was231.24mg/kg. The optimum conditions for alkali extraction were as following: pH11.5,temperature60℃, time2h, the ratio of water to stuff15:1; under this conditions theextraction rate of protein was69.85%, the content of protein was90.69%, and gossypolcontent was77.35mg/kg.The NSI of cottonseed protein concentrate (CPC) prepared with alcohol was25.84%.The result showed that the solubility of CPC was improved by three physicalmodification methods. The optimum conditions for water bath heating method were:heating temperature85℃, liquid to solid ratio o1:12, time8min, under these conditions theNSI was62.37%. The optimum conditions for ultrasound treatment were: ultrasonicfrequency28KHz, power150W solid-liquid ratio1:14, time15min, under these conditionsthe NSI was42.01%. The optimum conditions for microwave treatment were: power500W,the solid-liquid ratio1:14, time5min, under these conditions the NSI was41.28%. Theproperties of the modified products were compared respectively after three physicaltreatments. The results showed that water bath heating method had great influence on theCPC, including solubility, oil absorption, water holding capacity, emulsion and foaming,up to36.53%,54.08%,9.38%,23.05%,65.63%, but have little change in emulsion stability. Microwave radiation have significantly improved the solubility, water holding capacity, oilabsorption, emulsifying of the cotton protein isolate (CPI), up to5.0%,70.3%,6.5%,35.8%.After physical modification, surface hydrophobicity of the protein products hadincreased. The content of the free thiol was higher in the products prepared by water bathheating and microwave methods, and the ultrasonic product was rich in disulphide bond.The results of SDS-PAGE showed that physical methods had a little effect on the subunitstructures of modified protein. The FT-IR result of the CPC showed that the content ofα-helix decreased and the content of β-turn increased; accordingly, the content of randomcoil had changed a little after modification. To CPI, the content of α-helix and β-sheetdecreased while the content of β-turn and random coil increased.The modified cottonseed protein products were used to make meatball to replace somemeat, which could obviously reduce the meat cooking loss. When added5%CPC withheating modification, or3%CPI modified by microwave treatment, the obtained meatballsshowed better texture characters and higher sensory score.