Abstract
The taste of broad bean is associated with the seed components including sugars and free amino acids, but details changes in these components and their association with taste remain unknown. This study investigated changes in sugar and free animo acid concentrations during the development of broad bean seeds and the effects of these changes on the taste of these beans. The two cultivars (‘Amaekubo’ and ‘Uchikoshi Issun’) were grown by the conventional cultural method, and seeds were sampled at 5-day intervals from 35 days after flowering (DAF) for chemical analysis. Concentrations of fructose, glucose, sucrose and maltose peaked during 35–45 DAF with a yearly variation, while those of raffinose peaked at 50 DAF irrespective of year. Concentrations of stachyose and verbascose tended to increase until 55 DAF. The concentration of sucrose exceeded the level that would be expected to affect the taste of the seeds, whereas that of other sugars was far below that level, suggesting that sucrose is the most critical sugar affecting taste. Most of the free amino acids analyzed showed their peak concentrations around 45–50 DAF, and only glutamic acid and alanine showed concentrations that would be expected to affect the taste. Sensory tests demonstrated that seeds harvested around 45 DAF had the best taste. These findings indicate that the appropriate time for harvesting broad beans as a vegetable is around 45 DAF.
