ENZYME-RESISTANT STARCH .6. INFLUENCE OF SUGARS ON RESISTANT STARCH FORMATION

Solutions of glucose, ribose, maltose, and sucrose were added to autoc laved (1 hr at 121-degrees-C in excess water) wheat starch and high-am ylose corn starch. After storage of the starch gels for 20- to 350-min intervals, enzyme-resistant starch (RS) yields were determined. Sugar s 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 wh eat starch gels, the RS yields decreased from approximately 3.4% to ap proximately 2.8% when sucrose or glucose was present; they decreased t o approximately 2.5% in the presence of ribose or maltose. An increase in RS yield was observed with high-amylose corn starch. The experimen ts showed that the differences in gelatinization temperature, lipid co ntent, and apparent amylose content of the two starches were not the m ain causes of the different impact of sugars on the RS yields. RS qual ity of the isolated RS fractions, determined by X-ray diffraction and differential scanning calorimetry, was not affected by the sugars stud ied (except for a higher melting enthalpy of isolated RS when it was f ormed in the presence of ribose).