Cereal Chem 49:616 - 628. | VIEW
Starch Hydrolysis Under High Temperatures and Pressures.
K. Lorenz and J. A. Johnson. Copyright 1972 by the American Association of Cereal Chemists, Inc.
Starch was hydrolyzed in a closed system using elevated temperatures and pressures and water at neutral pH. Gas-liquid chromatography revealed the following alcohols: methanol, ethanol, isopropanol, propanol, isobutanol, and butanol. Total alcohol by volume varied from 1.54% at a hydrolysis temperature of 120 C. to 2.77% at a hydrolysis temperature of 180 C. Carbonyl compounds formed were: methanal, ethanal, propanal, butanal, pentanal, and hexanal; 2-propanone, 2-butanone, 2-pentanone, and 2-hexanone; 2- methylbutanal, 2-methylpentanal; and diacetyl, 5-hydroxymethylfurfural, and furfural. Total carbonyl compounds---116 p.p.m. at a hydrolysis temperature of 120 C. and 230 p.p.m. at 135 C.---increased to 69,000 p.p.m. at 155 C., and to 94,000 p.p.m. at 180 C. At the hydrolysis temperature of 180 C., the p.p.m. value approximated 10% of the reaction mixture. Total acidity increased and pH decreased as hydrolysis temperatures increased. The free fatty acids found were straight- and branched-chain, having chain lengths between C1 and C6. Identified were formic, acetic, proprionic, butyric, isobutyric, valeric, isovaleric, caproic, and isocaproic acids. As the hydrolysis temperature increased, the C5 and C6 fatty acids decreased, but formic and acetic acids increased. Small amounts of glucose and glucose polymers were formed by starch hydrolysis at temperatures of 120 degree and 135 C. and pressures of 32 and 80 p.s.i.g., respectively. Extensive starch hydrolysis to sugars occurred at a temperature of 155 C. and a pressure of 140 p.s.i.g. At 180 C. and 165 p.s.i.g., maximum glucose was produced, and small amounts of mannose, xylose, and arabinose were detected. Total sugar ranged from 11.2 mg. per 100 ml. at 120 C. to 265 mg. per 100 ml at 180 C. Those values corresponded to 0.37 and 8.83% sugar production, respectively, based on starch. Glucose comprised from 3.1 to 41.5% of the total sugar.