Abstract: The extraction of alkali-soluble proteins from Juglans mandshurica Maxim kernel waste left over after oil extraction with supercritical carbon dioxide was optimized using one-factor-at-a-time and orthogonal array design methods. The effects of NaOH concentration, material-to-solvent ratio, temperature and extraction time on the extraction yield of protein. It was found that the highest extraction yield of protein, 88.05%, was obtained after 1.5 h of extraction with 0.02 mol/L NaOH solution at a material-to-solvent ratio of 1:30 and 50 ℃. The isoelectric point of the extract obtained under these conditions was measured to be 4.5. SDS-PAGE analysis showed that the molecular weight distribution of alkali-soluble proteins from Juglans mandshurica Maxim kernels was mainly 100, 60, 36 kD and 20 kD.

Key words: Juglans mandshurica Maxim, alkali-soluble protein, extraction, SDS-PAGE, molecular weight