Hard-to-cook beans (Phaseolus vulgaris):: Involvement of phenolic compounds and pectates

Hard-to-cook (HTC) is a textural defect that affects legume seeds stored in adverse conditions. Phenolic acids were extracted from dehulled soft (control) and HTC beans. HPLC analyses of the phenolic fractions indicated the presence of caffeic, p-coumaric, sinapic, and ferulic acids. The highest content of phenolic acids was present as methanol-soluble esters in the control samples (approximately 45 times more than in HTC). Phenolic acids bound to the water-soluble pectin fraction were 2 times higher in HTC than in control beans, wheras the content of ferulic acid bound to the water-insoluble residue of the cell walls was 4 times higher in the control than in HTC samples. Through Fourier transform infrared spectroscopy accumulation of pectates and binding of phenolics to cell wall components were detected in HTC samples.