Effect of steeping time on the starch properties from ground whole corn

Abstract

Ground whole corn was steeped for various time intervals (8, 16, 24, 32 and 40 h) in SO 2 solution, at 52 °C. The isolated starch, obtained by corn wet-milling, was characterized determining starch yields and gelatinisation parameters such as onset ( T o), peak temperature ( T p), conclusion ( T c), enthalpy (Δ H) and peak height index (PHI). Damaged granules and the starch granule size were tested through microscopic techniques. The results obtained were compared with the control sample (whole corn kernels steeped during 40 h at same condition). Greater starch yields were obtained from ground corn than whole kernels, and they increased with longer steeping time, confirming the largest disrupting action of SO 2 in the protein matrix when using ground corn. Starch recovery levels varied from 95.7% to 98.4%, and they were also higher than ones from whole kernels (85.1%). Several differences were detected between the physical properties of the starch samples recoveries from corn ground at different steeping times and those of starch recovered from whole kernels. Great homogeneity in the size distribution of starch granules were reached by using steeping times from 16 to 32 h. Δ H values showed a slight increase with steeping time as well as PHI, in addition, a narrow range of gelatinisation temperature was obtained. Annealing, different size distribution, changes in the damaged granules and protein contents are responsible of the different starch properties.