Cotyledon thermal behavior and pectic solubility as related to cooking quality in common beans |
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Authors: | Irma Bernal-Lugo Carmen Parra Margarita Portilla Cecilia B. Peña-Valdivia Ernesto Moreno |
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Affiliation: | (1) Departamento de Bioquímica, Instituto de Biología; Universidad Nacional Autónoma de México, 04510 México D. F.;(2) Departamento de Fisicoquímica, Facultad de Química, Instituto de Biología; Universidad Nacional Autónoma de México, 04510 México D.F.;(3) Departamento de Botánica, Instituto de Biología; Universidad Nacional Autónoma de México, 04510 México D.F.;(4) Programa de Botanica, Instituto de Recursos Naturales, Colegio de Posgraduados, 56230 Chapingo, Mexico |
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Abstract: | The characteristic of proteins, starch and pectic substances in cotyledons of two bean cultivars varying in cooking time were determined to investigate their possible contribution to bean cooking quality. Both cultivars showed the same enthalpies of starch gelatinization but different protein denaturation enthalpies. The proportion of hot water soluble pectins was higher in Michigan, the cultivar with the lower cooking time, than in Ojo de Cabra, the cultivar with the higher cooking time. These results were not due to differences in pectin methylation or in the ratio of monovalent to divalent cations in the tissue, suggesting that in fresh beans the β-elimination reaction is not the sole or predominant route of thermal pectin degradation. Overall, this study indicates that varietal differences in bean cooking quality may be reflections of the rate of pectin loss during soaking/heating and that the thermal properties of starch and protein fractions seem to have a minor contribution. Researchers involved in this study propose that in fresh beans, the thermal pectin loss results from a two step mechanism: pectin enzymic breakdown during the bean soaking followed by thermal solubilization rather than β-elimination during the bean heating. |
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Keywords: | Bean thermal analysis Common beans Cooking quality Pectin Phaseolus vulgaris L |
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