Effect of sucrose on the thermomechanical behavior of concentrated wheat and waxy corn starch-water preparations

The rheological behavior of concentrated starch preparations from two diffe rent origins (wheat and waxy corn) was studied in the presence of sucrose b y dynamic mechanical thermal analysis (DMTA). Moisture contents ranged from 30 to 60% (w/w wsb), and samples contained 0, 10, or 20 g of sucrose for 1 00 g of the starch-water mixture. The storage modulus (G') changes during h eating depended strongly on water content (in the moisture range studied), and the importance of these variations was dependent upon the starch type. Sucrose addition resulted in a shift to higher temperatures of the increase in G' during heating. Differential scanning calorimetry (DSC) and electron -spin resonance (ESR) analyses were performed in parallel in order to relat e the viscoelastic changes to water migrations and to structural disorganiz ation of starch. Sucrose was found to increase the gelatinization temperatu re and enthalpy of both starches, implying a stabilization of the granular structure during heating. The sugar-water interactions do not appear to be the only way by which sucrose delays starch gelatinization. The obtained re sults suggest that sugar-starch interactions in the amorphous and/or the cr ystalline regions of the starch granules should be envisaged.