Study of various treatments to isolate low levels of cider proteins to be analyzed by capillary sieving electrophoresis

Abstract Four different sample treatments (ethanol precipitation, dialysis, ultrafiltration, and gel filtration) to isolate cider proteins were tested in this work. Purified cider proteins were analyzed by capillary sieving electrophoresis (CSE) using linear polyacrylamide as a sieving medium under optimized conditions; with this technique, separation, and molecular weight determination of proteins are possible. The electropherograms obtained in the protein analysis with each treatment were compared to choose the one that led to the best results. This was found to be ultrafiltration; many peaks were obtained in the electrophoretic profile and their spectra corresponded to a protein. Bradford analysis confirmed this choice. These results were compared with those obtained by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS‐PAGE), the molecular weights of the protein bands agreeing with the molecular weights of the electrophoretic peaks obtained with ultrafiltration.