Comparison of methods used to characterize water imbibition in hard-to-cook beans

The traditional gravimetric and volumetric methods of measuring water imbibition were compared to a new method, water-holding capacity, to study water uptake in black bean cotyledons with and without the hard-to-cook defect. Water-holding capacity was found to be more reliable in measuring water taken up by the cotyledon since the former methods measure gross water uptake, including a layer of bulk water existing between the seedcoat and cotyledons of hard-to-cook beans. Total water uptake, as measure by the water absorption method was greatest for hard-to-cook beans. Using the water-holding capacity method, however, hard-to-cook beans were found to bind approximately 25% less water during soaking than control beans

Hard-to-cook defect in black beans — effect of pretreatment and storage condition on extractable phenols and peroxidase activity

Includes abstract in FrenchPretreatments were studied to assess their effectiveness in controlling the development of the hard-to-cook defect in black beans during storage in conditions that promote hardening. Of the methods tested only irradiation significantly reduced the rate of hardening. Total extractable phenols and in vitro peroxidase activity were measured over the storage period to find if changes in their relative amounts could be related to the rate of bean hardening. Determinations of extractable phenols over storage time showed that they decreased in some samples that showed hardening but this trend was not seen in all of the hardening bean samples nor was it seen exclusively in the hardening bean samples. However, it is apparent that, within each treatment, phenol degradation proceeded more rapidly under high temperature, high humidity conditions. It was concluded that the measurement of total extractable phenols may not have been sufficiently specific to detect changes in the phenol fraction important in either lignification or tannin anabolism. Peroxidase specific activity in beans stored in conditions promoting the hard-to-cook defect increased during the initial storage period but then decreased, either due to inactivation or binding. High levels of extractable peroxidase activity was not related to a greater degree or rate of hardening