Comparative study on citric acid modified instant starches (alcoholic alkaline treated) isolated from white sorghum...

This study investigated the impact of citric acid modification combined with alcoholic-alkaline treatment on physicochemical, textural and rheological properties of sorghum and corn starches. Both starches were modified with citric acid (CA) using concentrations (20 and 40%) w/w and were named as SCA and CCA, respectively. SEM analysis revealed that CA modified CWS (cold water-soluble) starches had cracks and more sharp edges as compared to their native counterparts. In FTIR spectra a new peak at 1730.50 cm^-1 and 1733.12 cm^-1 confirmed formation of distarch esters for SCA40 and CCA40. Increase in swelling power of CWS starches was observed after citric acid modification. Textural analysis showed that SCA20 and SCA40 formed smooth and soft gels suggesting reduced retrogradation tendency of these starches. The broader linear viscoelastic region of CCA40 and SCA40 indicated high shear resistance and well dispersed behavior of CWS citrates. Moreover, it was observed that all CWS starches showed increase in storage modulus (G') and loss modulus (G″) values at higher frequencies indicating elastic behavior. CA modification conferred heat and shear stability to starches. This study provides the basic knowledge for the application of CA modified CWS starches in many instant, refrigerated and frozen food products.