Armazenamento de cultivares de feijão e seus efeitos na qualidade tecnológica dos grãos e nas propriedades do amido.

Abstract

Bean grains develops the hardening defect during storage, which is a result of chemical and enzymatic changes in the grain. This phenomenon is also known as hard-to-cook defect (HTC). The development of bean cultivars which presents lesser susceptibility to the hardening defect can be an alternative to reduce the decrease in technological quality of stored bean grains. Some studies have showed that changes in starch fraction are one of the factors responsible for HTC development. However, it is not well elucidated in literature. Concerning these aspects, this study aims to evaluate effects of storage period on technological properties of grains and on physicochemical, thermal and pasting properties of starch isolated from stored bean grains. It were used common beans from carioca group, cultivars BRS Estilo, BRS Horizonte, Pérola, BRS Pontal and BRS Requinte, and common beans from black group, cultivars BRS Campeiro, BRS Esplendor, BRS Grafite, BRS Supremo and BRS Valente, all produced in Capivara Farm of Embrapa Arroz e Feijão, countryside of Santo Antônio de Goiás, State of Goiás. After harvested and cleaned, four repetitions of 1 kg of grains were stored in cotton bags and maintained at 25±1ºC during 12 months. The first study evaluated technological properties of grains and the second one evaluated the properties of starch isolated from the beans. The cultivars BRS Horizonte, Pérola and BRS Pontal, from carioca group, and the cultivar BRS Valente, from black beans group, showed the lower increase in cooking time after 12 months storage. The grains of the cultivar BRS Requinte (carioca bean) presented lower susceptibility to darkening. The starch properties varied between the cultivars. The swelling power, the gelatinization enthalpy, the final and holding viscosities, the peak viscosity, the breakdown viscosity and the setback viscosity increased in stored beans as compared to non-stored beans, with some exceptions. The properties of starch isolated from beans does not presents correlation with increasing cooking time and/or decreasing hydration coefficient.