Effect of Ultrasound Treatment on Structural and Physical Properties of Native Maize Starch

Abstract

The focus of this work was to evaluate the differences between the thermal and mechanical effects generated by ultrasound waves on the properties of corn starch, which facilitate the subsequent enzymatic hydrolysis for the generation of porous starches. The results showed that both the thermal and mechanical effects have the capacity to disorganize/alter the structure of starch, impacting on its properties. Characteristics such as particle size, pasting and thermal properties (peak viscosity 1400-1800 cp. and gelatinization enthalpy 4.5-11 J/g) of starch and water absorption were the most affected, while crystallinity was practically unmodified (crystallinity % 23-25). The thermal effect induced by the ultrasound treatment caused most of the alterations in the properties of corn starch. It was associated with the partial gelatinization of the material due to an increase in the system´s temperature (up to 65° C). The effect of the mechanical phenomenon of the treatment by ultrasound waves contributed to a lesser extent compared to the thermal effect. The mechanical effect can extend over time, without the aggravating factor of causing starch gelatinization. The combination of both effects could synergistically modify the granular structure of starch. In conclusion, ultrasound waves as a pre-treatment to enzymatic hydrolysis can cause structural disorganization of starch granules and facilitate the subsequent enzymatic attack for the production of porous starches.