Relationship of Loss of Membrane Functionality and Hard‐to‐Cook Defect in Aged Beans

Abstract

ABSTRACT Microsomal membranes were prepared from fresh beans ( Phaseolus vulgaris ) and from samples kept 9 mo at various temperatures and humitidies. Increasing storage severity produced progressively hard‐to‐cook (HTC) beans as well as higher solids loss and lower water‐holding capacity during soaking. Membrane phase transition temperature (PTT), calcuated from spin label electron paramagnetic resonance data, also increased and showed a highly significant (r = 0.997) correlation with cooked hardness. Fatty acid analysis of membrane lipids demonstrated higher PTT values were due to a significant increase in proportion of saturated fatty acids. These data reflect membrane deterioration during aging that could explain solids loss and water‐holding capacity changes. Changes in the membrane may be the primary event in initiation of the HTC defect.