Solutions of glucose, ribose, maltose, and sucrose were added to autoclaved (1 hr at 121 C in excess water) wheat starch and high-amylose corn starch. After storage of the starch gels for 20- to 320-min time intervals, enzyme-resistant starch (RS) yields were determined. Sugars had an influence on RS levels in starch gels, only when added in high concentrations (final starch-water-sugar ratio of 1:10:5, w/w). In wheat starch gels, the RS yields decreased from approximately 3.4% to approximately 2.8 % when sucrose or glucose was present, and they decreased to approximately 2.5 % in the presence of ribose or maltose. An increase in RS yield was observed with high-amylose corn starch. The experiments showed that the differences in gelatinization temperature, lipid content, and apparent amylose content of the two starches were not the main causes of the different impact of sugars on the RS yields. RS quality of the isolated RS fractions, determined by X-ray diffraction and differential scanning calorimetry, was not affected by the sugars studied (except for a higher melting enthalpy of isolated RS when it was formed in the presence of ribose). | |
