Drying Kinetics and Sorption Isotherms of the Nejayote

The nixtamalization is an alkaline cooking process in corn tortillas industry that uses large quantities of water (5:1 corn weight) and producing a byproduct called nejayote. In this work, drying kinetic of insoluble fraction from nejayote was obtained using a hot air cabinet dryer at 60, 75, and 90°C. The air rate and water content were 1.5 m/s and 0.028 kg of water/kg of dry air, respectively. Sorption isotherms were measured by the COST method with sulfuric acid solutions at 30, 45 and 60°C. Results showed a difference in drying kinetics/drying time between drying temperatures of 60 and 75°C, and practically no difference between 75 and 90°C. This was probably due to the development of a superficial crust on the product. The shape of sorption curves was as expected; no temperature effect was identified but it is a common behavior for products with high sugar content. Finally the sorption isotherm was predicted based on primary chemical compounds (carbohydrates, proteins, crude fiber, and calcium hydroxide).