Physicochemical and Structural Properties of Two Bean Varieties which Differ in Cooking Time and the HTC Characteristic

Abstract

Physicochemical and structural properties as well as proneness to hardening were assessed in normal (Mayocoba) and slow (Flor de Mayo) cooking varieties of beans. Storage and chemical procedures were used for determination of the hardening of both samples. Normal and slow cooking varieties had cooking times of 58 and 90 min, respectively. During storage under high temperature and humidity the normal variety exhibited a four-fold increase in cooking time while that of the slow cooker increased nine-fold. Chemical hardening caused an increase in cooking time of 3.4- and 5.7-fold for normal and slow beans, respectively. The former had lower percentage and thinner seed coat, and higher water absorption in the whole seed and seed coat, but not in the cotyledons, as compared to the latter. Chemical analysis demonstrated a much lower tannin content in fresh and hardened seed coats and cotyledons of the normal cooker, but more phytic acid content in cotyledons than in the slow. In fresh and hardened states the normal cooking variety had lower gelatinization and protein denaturation temperatures and enthalpies than the slow. SEM revealed important structural differences between both varieties and conditions. These characteristics may be used as identifying features linked to hardening proneness.