Microscopic evidence for pectin changes in hard-to-cook development of common beans during storage

In this study, pectin changes during Red haricot bean storage under high temperature and humidity conditions were investigated to understand the hard-to-cook (HTC) development from a microstructural point of view. First, ensure repeatability microscopy results, classification fresh stored beans (aged at 35 °C 83% relative humidity) into different hardening levels (the Non-aged, Aged Very-hard aged sample) was performed based on texture values cooked half-cotyledons. Cell wall strength cotyledons evaluated, showing that samples (HTC seeds) exhibit stronger cell walls with more/stronger pectic cross-linkages than Non-aged sample. After sequential extraction aiming removing fractions solubility, autofluorescence immunolabeling JIM7, LM9 2F4 epitopes in residual materials examined. Upon ageing, exhibited an increased Ca2+-pectin ferulic acid-pectin crosslinking, these complexes being accumulated primarily intercellular spaces. The results suggest contribution both pectin-cation-phytate hypothesis involvement phenolic-pectin crosslinks HTC cotyledon common beans.