In this study, the effect of high energy milling using a Spex ball mixer mill on some functional properties of cassava starch (Manihot utilissima) and jicama starch (Pachyrrisus erosus) were investigated. The properties of individual granules were strongly influenced by the high moisture of ball milling (friction and heat) and physicochemical properties of their amorphous and crystalline zones. High energy milling resulted in a partial fragmentation of the starch granules, increasing the water absorption index (WAI) and the water solubility index (WSI). Increasing moisture content the viscosity was decreased, attributable to the fragmentation of starch granules produced by the milling and favored by the increase of moisture content. The crystallinity of cassava and jicama starches milled with high moisture contents and longer milling times was decreased. Thermal properties of both ball-milled starches were modified. The enthalpies were lower than native starch indicating that ball milling destroys the crystallinity and double helical order arrangements. Also, the resolution of the peaks was slightly decreased. Ball-milled jicama and cassava starches showed some functional characteristics of gelatinization that possibility their use in food systems as stabilizing, additives, moisture retainers and thickeners. (c) 2006 Elsevier Ltd. All rights reserved.