Water sorption characteristics were investigated using both the GAB and Smith models for commercial starch products to determine their involvement in the extent of gelatinization. The GAB monolayer water content, W(m), correlated well with the Smith parameter w(b), whereas the R(2) coefficient of W(m) with the Smith parameter w' exhibited a weaker correlation. The relationship between W(m) and the multilayer water content, MC, could be expressed with R(2) coefficients greater than 0.840 and the ratio of W(m) to MC was constant at 1:2-1:3, irrespective of variations in ingredients and sorption processes. Thus, the coverage of particular water binding sites is considered to be simple, despite the various components of commercial starch products. In addition, both W(m) and MC may be involved in the extent of gelatinization: swelling capacity and viscosity were intimately involved in the early stage of gelatinization. (C) 2010 Elsevier Ltd. All rights reserved.