Study on Structural and Physicochemical Properties of Modified Corn Starch: Comparison of Ultrasound, Stirring, and Lactic Acid Treatments

Ultra-sonication has been growingly utilized in starch modification as a green and non-thermal technology. In this research, the effect of ultrasonic, stirring, and lactic acid treatments alone and with their combination (binary and ternary) on the properties and structure of corn starch is investigated. In the ternary treatment, degree of substitution of lactate on the polymeric chains of the starch is increased, inducing an esterified structure, which imparted to the modified starch a higher swelling power, water holding capacity, water absorption index, oil absorption rate, and amylose content along with lower viscosity and activation energy of gelatinization than native starch and the rest of the treatments. Also, the in vitro starch digestibility test with ternary treatment exhibits lowest rapidly digestible starch fraction, and highest slowly digestible starch and resistant starch fractions. The XRD patterns demonstrate a reduction in crystallinity percentage of the modified starch by the ternary treatment compared to native starch. The images of SEM indicate that ultra-sonication and acid hydrolysis result in the damage of granules' surface, while sample agitation by stirring causes no change. Esterification of corn starch is proved by FT-IR. Starch modification by the proposed ternary treatment can be utilized in production of low-calorie foods.