Physiochemical Quality and Sensory Characteristics of koji Made with Soybean, Rice, and Wheat for Commercial doenjang Production

The purpose of this study was to compare the physiochemical quality characteristics and sensory profiles of three types of koji: soybean, rice, and wheat koji. Koji is made by inoculating Aspergillus oryzae following the standard method of manufacturing. The physiochemical characteristic and sensory profiles were performed after fermenting samples of koji for a 72 h period. The physiochemical quality characteristics that were tested include pH, moisture content, color, acidity, TA, amino-type nitrogen content, reducing- and total-sugar content, and alcohol content; the enzymatic activities that were tested include amylase (α- and β-) and protease (neutral and acidic) activities. A descriptive sensory analysis was conducted on three types of koji with a highly trained sensory panel (n = 7) using the Spectrum(TM) Method. Differences in physiochemical and sensory profiles were observed on three koji samples (p < 0.05). Soybean koji had higher values in acid and TA, while rice koji had the highest values in reducing and total sugar, at 90.3 mg/g and 107.5 mg/g respectively. Wheat koji had the lowest values in protease activities. The flavor profile of soybean koji was characterized by bean sprout, cracker, and cheonggukjang aromatics; that of rice koji was characterized by overripe banana, solvent, syrup, and parboiled rice aromatics; and that of wheat koji was characterized by woody and roasted aromatics.