AN IMPROVED PROCESS FOR ISOLATION OF CORN FIBER GUM

Sequential alkaline extraction and alkaline hydrogen peroxide (AHP) bl eaching have been used to prepare corn fiber gum in yields ranging fro m 21 to 40%, depending on the pH of the extraction medium. The pH was adjusted by using different ratios of NaOH and Ca(OH)(2). The whitest product was obtained after AHP bleaching of the extract obtained using the lowest pH value. In order for the product gum to give its charact eristic clear and low viscosity solutions, it was necessary to remove starch from the corn fiber substrate using alpha-amylase. The water-in soluble hemicellulose A fraction, a minor component, was removed by ne utralizing AHP-treated extracts before ethanol precipitation of the us eful hemicellulose B (corn fiber gum) fraction. At ambient temperature , AHP bleaching was near optimal after approximate to 2 hr under the p rocessing conditions used. High ratios of arabinose (39%) to xylose (5 0%) were present in the corn fiber gum extracted under various alkalin e conditions, and the H2O2 processing step did not significantly alter these ratios. The same low levels of galactose (7%) and glucuronic ac id (4%) were present regardless of the extraction conditions. Molecula r mass of the corn fiber gum preparations ranged from 2.78 x 10(5) for the material extracted with Ca(OH)2 to 3.94 x 10(5) for the material extracted with NaOH. Molecular mass was unaffected by the H2O2 present in the second processing step. As expected for a carbohydrate polymer with a rather low uronic acid content, solution viscosities were unaf fected by the presence of salt.