Detailed analysis of seed coat and cotyledon reveals molecular understanding of the hard-to-cook defect of common beans (Phaseolus vulgaris L.)

• Published in: Food chemistry Vol. 210; pp. 481 - 490
• Main Authors: Yi, Jianyong, Njoroge, Daniel M., Sila, Daniel N., Kinyanjui, Peter K., Christiaens, Stefanie, Bi, Jinfeng, Hendrickx, Marc E.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.11.2016
• Subjects: Calcium; Cations, Divalent - chemistry; Common beans; Cooking - methods; Cotyledon - chemistry; Extractability; Hardness; Humidity; Molar mass; Neutral sugar; Pectin; Pectins - chemistry; Phaseolus - chemistry; Polysaccharides - analysis; Polysaccharides - chemistry; Seeds - chemistry; Common beans; Pectin; Extractability; Calcium; Neutral sugar; Molar mass
• ISSN: 0308-8146; 1873-7072
• DOI: 10.1016/j.foodchem.2016.05.018

•Pectic polysaccharides play a significant role in development of the HTC defect.•Sugar composition in seed coats dramatically differed from that in cotyledons.•Degree of methoxylation of chelator extractable polysaccharides decreased in HTC beans.•Water extractability of non-starch polysaccharides decreased in HTC beans.•Increased Ca2+-pectic polysaccharide cross-linkage contributed to the HTC defects. The hard-to-cook (HTC) defect in legumes is characterized by the inability of cotyledons to soften during the cooking process. Changes in the non-starch polysaccharides of common bean seed coat and cotyledon were studied before and after development of the HTC defect induced by storage at 35°C and 75% humidity for 8months. Distinct differences in the yields of alcohol insoluble residues, degree of methoxylation (DM), sugar composition, and molar mass distribution of non-starch polysaccharides were found between the seeds coat and cotyledons. The non-starch polysaccharide profiles, both for seed coats and cotyledons, significantly differed when comparing HTC and easy-to-cook (ETC) beans. In conclusion, differences in the structure, composition and extractability of non-starch polysaccharides between the ETC and HTC beans confirmed the significant role of pectin polysaccharides in interaction with divalent ions in the HTC development, which consequently affect their cooking behaviors.