Physicochemical and functional properties of protein isolate obtained from cottonseed meal

[Display omitted] •The preparation methods of cottonseed meal influenced the properties of CPIs.•α-Helix, β-turn structures of CPI transform into β-sheet ones due to denaturation.•CPIs had two X-ray diffraction peaks and one endothermic peak.•Proteins of SCM exhibited less denatured and desirable functional properties. To investigate the effect of preparation methods of cottonseed meals on protein properties, the physicochemical and functional properties of proteins isolated from hot-pressed solvent extraction cottonseed meal (HCM), cold-pressed solvent extraction cottonseed meal (CCM) and subcritical fluid extraction cottonseed meal (SCM) were investigated. Cottonseed proteins had two major bands (at about 45 and 50kD), two X-ray diffraction peaks (8.5° and 19.5°) and one endothermic peak (94.31°C–97.72°C). Proteins of HCM showed relatively more β-sheet (38.3%–40.5%), and less β-turn (22.2%–25.8%) and α-helix (15.8%–19.5%), indicating the presence of highly denatured protein molecules. Proteins of CCM and SCM exhibited high water/oil absorption capacity, emulsifying abilities, surface hydrophobicity and fluorescence intensity, suggesting that the proteins have potential as functional ingredients in the food industry.