Aroma characteristics of fermented Korean soybean paste (Doenjang) produced by Bacillus amyloliquefaciens

Four strains of Bacillus amyloliquefaciens with high proteolytic, fibrinolytic, and angiotensin converting enzyme (ACE) inhibitory activities were used to make Bacillus-koji suitable for the production of functional doenjang. Volatile compounds in Bacillus-koji doenjang were analyzed by headspace-solid phase microextraction-GC-MS (HS-SPME-GC-MS) to compare the aroma profile with those of commercially produced doenjang made with traditional meju and with modified koji. Extraction temperatures for SPME were adjusted to 30 and 90°C. Commercial samples contained significantly more esters than Bacillus-koji doenjang and demonstrated a more complex volatile compound profile. Pentanoic acid, butanoic acid, or 2/3-methyl butanoic acid, known as off-flavor compounds in doenjang, were not detected in one of the Bacillus-koji doenjang when extracted at 30°C. From the sensory test results, the cheese character was less intense in Bacillus-koji doenjang than commercial samples, although not all sensory properties projected a significant difference.