Direct link between specific structural levels of starch and hydration properties

Enhanced water retention capacity (WRC) of physically modified flours is often attributed to a particle size reduction, neglecting potential influences of altered amylose/amylopectin ratio and crystallinity of starch. Therefore, this study aims to investigate the impact of altered amylose/amylopectin ratio and crystallinity on WRC by modifying wheat flour using a cryogenic (CG) and an ultra-centrifugal grinder (UCG). With increased grinding time in CG and rotation speed in UCG, WRC rose linearly. Neither for CG nor for UCG modified flours a linear dependency of amylose/amylopectin ratio on WRC was detected. Additionally, no linear relation between crystallinity and WRC of UCG modified flours was determined (R² = 0.03). For both modifying methods, however, linear dependency of WRC and starch modification degree was found. Through this systemic approach it was proven that WRC of modified flours can exclusively be attributed to alterations of surface properties.