Effect of steeping time and calcium hydroxide concentration on the water absorption and pasting profile of corn grits

• Steeping time and calcium hydroxide content had significant effects on water absorption and pH of corn grits.
• Large starch granules showed cavities which facilitate water diffusion into the granule.
• Water diffusion significantly influences the pasting properties of steeped corn grits.
• Viscosity correlated with water absorption and increased with steeping time and calcium hydroxide content.
• Water diffusion in corn grits was influenced by contact area, which facilitates diffusion.

Water diffusion in corn is important in both dry and wet milling because it is one of the factors that determine the functionality and quality of any final product for which this cereal is intended. The diffusion of water into the starch granule will be affected by the type of solvent used, the temperature, and the size and shape of the starch granule. Therefore, the aim of this investigation was to assess the effect of steeping corn grits at room temperature in a solution with and without the addition of calcium hydroxide on the hydration and pasting properties. We evaluated the moisture gain, pH change, viscosity profile, and the microstructure of the endosperm relative to the steeping time of corn grits with and without calcium hydroxide. Corn grits steeped in water without calcium hydroxide showed lower water absorption (35 g/100 g) than those steeped with 1 g Ca(OH)2/100 g (38 g/100 g) and 2 g Ca(OH)2/100 g (40 g/100 g). Electron micrographs show that the starch granule size in corn grits increases due to water absorption. Viscosity increases with steeping time and the calcium hydroxide concentration shows a correlation (r = 0.7) with water absorption. We calculated effective diffusion coefficient of corn grits with and without calcium hydroxide concentration, solving Fick’s equation for a sphere. Water diffusion into the starch granule is an important step that significantly influences the pasting properties of the corn grits.