Dual modification of normal corn starch by cross-linking and annealing: investigation of physicochemical, thermal, pasting, and morphological properties

Starch is a widely used carbohydrate polymer whose functional properties can be easily modified through chemical or physical modification. Modification can expand the use of starch in various industries such as food, pharmaceutical and textile industries. In this paper, the modification of normal corn starch through cross-linking with Sodium trimeta-phosphate/sodium tripolyphosphate at concentrations of 6 and 12% with or without pretreatment with annealing (Ann) at two distinct times (12 or 24 h) was investigated. The results showed that modification treatments increased the phosphorus content up to 233.01 ppm. Clarity and swelling power of the modified starches were about 68.4-77.1% and 29.3-42.7% less than native starches, respectively. Dual modified starches showed some changes in morphology determined by scanning electron microscopy. DSC results exhibited that the cross-linking and Ann processes caused a significant increase in the gelatinization onset temperature, while enthalpy (up to 20.2%) and temperature range of gelatinization (up to 29.8%) decreased in all cases. Regarding RVA data, dual modifications provided lower breakdown and setback viscosities compared to the cross-linking alone. Our study showed that cross-linking treatment and Ann pretreatment increases the thermal stability of corn starch and provides the possibility of its application in food products such as frozen and canned foods.