Beans (Phaseolus vulgaris L.) hardening phenomenon: cell wall polysaccharides / Fenômeno de endurecimento de feijões (Phaseolus vulgaris L): polissacarídeos da parede celular

AUTOR(ES)
DATA DE PUBLICAÇÃO

1998

RESUMO

Common beans is one of the most important source of nutrients for the world population, mainly in developing countries. Nevertheless, they have severaI undesirable characteristics, such as antinutrients components and facility to acquire textural defects when stored under inadequate conditions. High temperature and humidity of storage cause the development of hard-to-cook phenomenon, characterized by extended cooking time for cotyledon softening and responsible for economic and nutritional losses. In order to study this phenomenon, soluble cell wall material (SCWM) and insoluble cell wall material (ICWM) were isolated from cotyledons of beans stored at 4°C, room temperature (RT) and 37°C/75% relative humidity (RH) and analysed about their sugar composition. ICWM was fractionated with aqueous solutions of chelating agents and hidroxide solutions gradient. Each fractions were analysed about their sugar composition. Control beans cotyledon contained 12.3% of ICWM, composed mainly for polysaccharides solubilized by NaOH 4.0N (29.4%), composed in its majority of arabinose (55.0%), xylose (10.3%), uronic acid (18.9%) and polysaccharides solubilized by NaOH 0.5N (16.8%) and NaOH 1.0N (17.2%), composed in most part of glucose (92.1% and 90.7% respectively). About 9.0% of cell wall of control beans is composed by SCWM, that contain arabinose (38.6%), uronic acids (23.4%), galactose (12.7%) and xylose (11.2%). The cell wall composition showed alterations with aging in beans stored at RT and 37°C. Cotyledon ICWM of beans stored at RT and 37°C showed a increase in arabinose (44.8% and 31.7%), uronic acid (54.3% and 42.9%) and xylose contents (38.6% and 27.2%), originating of pectins and decrease of glucose contents (64.0% and 48.6%), probably originating by hemicellulose. SCWM showed reduction mainly in arabinose contents (40.2% and 15.9%). Besides, beans stored at RT and 37°C, showed increase in cooking time (2.3 and 8 times higher than control) and decrease in germinability (17% and 100%). It could be a indication of cross-linking formation and pectins insolubilization during aging, contributing with bean hardening. Beans stored at 4°C showed alterations in germinability and fractionation profile, but didnt show considerably alterations in cotyledon ICWM and SCWM sugar composition.

ASSUNTO(S)

bioquímica de alimentos polissacarídeos polysaccharides cromatografia a gás textura phaseolus vulgaris l. gas chromatography texture phaseolus vulgaris l. food biochemistry

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