Influence of Storage Conditions on L-DOPA Content and CotyledonTissue of Mucuna Beans (Mucuna Pruriens)

Abstract

We investigated the effects of storage on the hardness, L-DOPA content, and tissue structure in Mucuna beans (Mucuna pruriens). Hardening defect tended to occur as a result of storage at high temperature and high humidity (30°C/75% RH), at low temperature and low humidity (4°C/35% RH), and at room temperature (20°C/60% RH). Beans that were kept refrigerated (4°C/80% RH) showed the smallest change. The L-DOPA content of aged beans was hardly changed even when stored at high temperature and high humidity, but cooking reduced the amount to about one third. Analysis of the pectin fraction in alcohol insoluble solids revealed that the hardening of Mucuna did not involve the formation of crosslinks by pectin and divalent cations, suggesting that there was an interaction between Ca²⁺ and cell wall polysaccharides, such as hemicellulose and cellulose. Furthermore, differential scanning calorimetry and scanning electron microscopy suggested that the denaturation of proteins around starch granules disturbed swelling, resulting in insufficient gelatinization of the starch during heating.