Properties of Doenjang (Soybean Paste) Fermented with Multiple Starters

Abstract

Multiple starters consisting of two Bacillus amyloliquefaciens strains (MJ1-4 and EMD17),Pichiafarinosa SY80, and Rhizopus oryzae were used for Doenjang making. Bacillus strainswere selected based on their abilities to inhibit toxinogenic fungi and Bacillus cereus,fibrinolytic activity, and their ability to confer good flavor to Cheonggukjang. P. farinosaSY80 and R. oryzae, previously isolated from soy sauce, were selected because they were notinhibited by two bacilli. Doenjang was prepared by inoculation of multiple starters (A1Doenjang). Control Doenjang was prepared by inoculation of B. subtilis KACC 16750 (Nattostrain) and Aspergillus oryzae KCCM 60166 (A2 Doenjang). Another control (A3 Doenjang)was prepared by inoculation of microorganisms present in rice straw. Doenjang samples werefermented for 70 days at 20℃. pH of 3 samples decreased from the initial value of 6.4 to5.8~6.0 and titratable acidity (TA) increased from 0.6 to 1.1~1.3. The amount of amino-typenitrogen increased during fermentation. There were slight differences in moisture, crude-protein,and crude-fat contents after 70 days. Contamination of fungi was observed only in A3Doenjang and B. cereus was not detected from all 3 samples. A1 Doenjang showed thehighest fibrinolytic activity and A2 Doenjang the second. These results indicate that Doenjangmade with carefully selected starters was functionally improved and microbially more safe.