Waxy maize, corn and cassava starch: Thermal degradation kinetics

The use of starches in food and materials areas requires processing at elevated temperatures. The study of thermal degradation kinetics of starches and their relationship with amylose content, crystallinity, viscosity and thermal properties can help to design the processing conditions. The crystallinity and ordering of corn, cassava and waxy maize starches determined by means of X-ray diffraction (XRD) and Fourier Transform infrared spectroscopy (FTIR), respectively. Correlation between crystallinity, viscosity and amylose content was found. The kinetic parameters (activation energy (E_a), order and pre-exponential factor (A)) were determined through three models: Coats-Redfern, Broido and van Klevelen, using the best linear fit method. The overall order of thermal degradation process of all the starches was found to be of first order. The Ea increases following the order: corn < cassava < waxy maize. The higher A and E_a values found for waxy maize starch indicate that structural differences influence the thermal degradation process. (author)