Umami taste characteristics of water extract of Doenjang, a Korean soybean paste: Low-molecular acidic peptides may be a possible clue to the taste

► We determined the umami taste characteristics of doenjang, a Korean soybean paste. ► Low-MW acidic peptides (1000>MW⩾500) are responsible for higher umami taste characteristics. ► Taste-active fractions had a highest molar ration of Glu and Asp. We investigated the taste characteristics of doenjang water extract (DWE) for component compounds that contribute to its taste. A 1% DWE solution elicited the highest umami taste ratings in a taste profile test. A 3% solution of DWE was used as substitute for 9.4% of monosodium glutamate in a taste soup base, and it masked the bitter taste of hydrolysed animal protein when mixed in solution. DWE was fractionated, based on molecular weights, and fraction IV (F-IV; 1000>MW⩾500) had the highest peptide contents and elicited the strongest umami taste. The acidic peptide fraction of F-IV elicited the strongest umami taste. The major bound-type amino acids in DWE, F-IV and the acidic peptide fraction were Glu and Asp. These data show that the umami taste characteristics were a result of the low molecular weight acidic peptides naturally produced during the fermentation of soybeans.