Physicochemical properties and structural characteristics of whole grain Oryza sativa L. with different treatments.

Physicochemical properties and structural characteristics of whole rice flours with different treatments (soaking, germination and extrusion cooking) were studied. Water solubility, water absorption, crystallinity, adsorption isotherms (BET and GAB models), and glass transition temperature of the samples were determined. Water solubility and water absorption were enhanced by extrusion cooking process (3.17-4.98 vs. 24.1-53.76 g/100 g and 2.77-3.05 vs. 4.46-7.04 ml/g, respectively), but crystallinity was decreased (30-33 vs. 4-16%). Adsorption isotherms showed that extruded samples exhibited higher equilibrium moisture content as compared with their corresponding non-extruded samples (5.0-19.2 vs. 4.0-16.1 g water/g solids). There were no changes in glass transition temperature values in the studied moisture range (3.8-16 g/100 g). These results allow the correct use of whole rice flours with different treatments in foods and also contributed to the knowledge of stabilization of the products.