Impregnation of normal maize starch granules with ionic hydrocolloids by alkaline dry heating

Abstract

Dry heating of starch-hydrocolloid mixtures under different pH conditions was investigated to improve the physicochemical properties of the native starches by impregnation with the hydrocolloids. Normal maize starch was dry-heated in the presence of 1% xanthan or sodium alginate at pH 5.5 or 10. Alkaline dry heating at pH 10 resulted in a lower pasting temperature and higher peak viscosity in the presence of xanthan. After alkaline dry heating, hydrocolloids were observed on the surface of starch granules and on the inner side of the starch granules by scanning electron microscopy and confocal microscopy, respectively. High swelling power and solubility were induced by alkaline dry heating in the presence of xanthan or sodium alginate. Changes in the textural properties of the stored starch gels, such as low hardness, springiness, cohesiveness, and chewiness of stored starch gels, were observed by incorporating xanthan and sodium alginate during dry heating. The presence of xanthan during alkaline dry heating decreased the storage modulus and loss modulus but increased loss tangent, indicating a less rigid, more viscous, less structured material. Impregnation of the starch granules with hydrocolloids was more pronounced with dry heating under basic conditions than acidic condition, resulting in changes in the physicochemical and rheological properties of normal maize starch.