Changes in mass transfer, thermal and physicochemical properties during nixtamalization of corn with and without agitation at different temperatures

摘要

White dent corn was nixtamalized in a Ca(OH)_2 [1.2% (w/v)] solution, at a 1:3 corn/water ratio, at 70, 80, 90 and 100 ℃ for 1 h, with and without mechanical agitation. After cooking the nixtamalized grains were steeped for 48 h. During cooking, kinetics of soluble and suspended solids and total sugar were determined, while that in the grain was determined the pericarp removed. During steeping, water and calcium absorption kinetics were determined in grains and apparent diffusion coefficients were calculated using Fick's second law. Changes in thermal properties were determined. Cooking temperature and agitation had significant effects on the chemical and physical properties of grains and nejayote. Soluble and suspended solids and total sugar in nejayote showed a linear trend over time for different temperatures, while pericarp removal during both cooking and steeping reached over 90%. Cooking temperature had a significant effect on water and calcium absorption in grains. Calcium and water diffusion were described adequately using Fick's model. Water and calcium diffusion coefficients values were 2.07-3.52 × 10~(-10)m~2 s~(-1) and of 0.332-1.43 × 10~(-10)m~2s~(-1), respectively. Gelatinization temperature and enthalpy were significantly influenced by the temperature and time of the cooking.