Fractionation and characterization of soluble proteins from cider

Soluble protein characterization of cider was carried out by reversed-phase high performance liquid chromatography (RP-HPLC) and sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE). RP-HPLC protein separations by means of their hydrophobicity were performed on a C18 (250×4.6 mm i.d., 5 μm, 300 Å) column, using a mobile phase of acetonitrile-acidified water in gradient mode. The protein identifications were carried out by UV spectra analyses. The SDS–PAGE patterns showed several bands with molecular weights between 20 000 and 97 000 daltons. Several methodologies were tested to isolate and preconcentrate the cider proteins prior to their separation and detection. The best results were obtained using dialysis to remove low molecular mass contaminants followed by lyophilization to concentrate the proteins.