Abstract
Mucuna beans, a high-yielding legume variety, contain L-3, 4-dihydroxyphenylalanine (L-DOPA), at a high concentration of 3-9% in dried seed meal. L-DOPA is a potentially toxic compound, needs to be removed from the beans prior to consumption of Mucuna beans as food. We investigated the preparation conditions and the fermentation process of miso for reducing L-DOPA concentrations in Mucuna beans to a safe level. Four types of miso prepared from Mucuna beans and soybeans at different conditions were considered: salty, with rice koji; medium-salty, with rice koji; sweet, with rice koji; and medium-salty, with barley koji. All Mucuna bean miso types were produced through a fermentation process similar to that for soybean miso, according to pH, acidity I and II, protein solubility, and colorimetric values. The amount of L-DOPA in Mucuna bean miso remained at 0.14-0.26 g/100 g in wet weight of miso at the beginning of the fermentation, and decreased to 0.01-0.15 g after one month; L-DOPA could not be detected at the end of the fermentation. The medium-salty-type Mucuna bean miso using rice koji had the highest sensory evaluation, antioxidant activities by DPPH and ORAC methods showed approximately 1.7-fold and 4.5-fold higher than those of soybean miso, respectively. These results suggest that Mucuna bean miso has functional antioxidant activity and is safe for consumption.
