황기(Astragalus membranaceus)를 첨가한 청국장의 품질 특성을 조사하였다. 수분함량은 발효가 진행됨에 따라 감소하였고 조단백은 약간 증가하였다. pH는 발효초기에 약간 감소한 후 증가하는 경향을 보였으며, 아미노태질소는 24시간까지는 황기 첨가구가 높았으나 이후에는 대조구가 높았다. 색도(명도, 적색도, 황색도)는 감소하였다. 발효온도 $40^{circ}C$에서 ACE 저해도는 대조구 48시간 86.0%, 황기첨가구 24시간 95.3%로 가장 높은 값을 나타내었으며 발효시간이 경과함에 따라 점점 감소하였다. $40^{circ}C$에서 48시간 발효 시 혈전 용해능은 대조구 100.7%, 황기 첨가구 74.4%로 나타났다. $40^{circ}C$에서 48시간 발효 시 청국장의 향기성분인 2,6-dimethyl pyrazine양은 대조구 19.0 ppm, 황기 첨가구는 3.3 ppm 이었으며, 관능검사는 황기첨가구의 전반적 기호도가 7.67(p<0.001) 으로 대조구에 비해 높았다.
This study investigated the effects of a Hwangki (Astragalus membranaceus) extract on the quality of Chungkukjang fermented by Bacillus subtilis KCCM 12148, at 30, 40, and $50^{circ}C$, for 4 days. Changes in moisture contents, protein levels, pH values, ammonia-type nitrogen levels, color, angiotensin-converting-enzyme (ACE) inhibition rates, and fibrinolytic activities, were all determined. For both control and test, the moisture contents decreased gradually with time and the protein levels increased slightly. The pH values fell at the beginning of fermentation and then rose. The content of ammonia-type nitrogen was higher in Hwangki with Chungkukjang than in control, until 24 hr after fermentation commenced. After that time, the content of ammonia-type nitrogen control was higher in the control than in the Hwangki with Chungkukjang sample. Color features, such as lightness, redness, and yellowness, all decreased during fermentation, in both control and test. The highest ACE inhibition rates during fermentation at $40^{circ}C$ were 90.9% in the control (48 hr after fermentation commenced) and 95.3% in Hwangki with Chungkukjang(24 hr). Fibrinolytic activities of Chungkukjang and Hwangki Chungkukjang were 100.7 and 74.4% respectively. The content of 2,6-dimethyl pyrazine in the control was higher than that in Hwangki with Chungkukjang. Sensory evaluationtests showed that the addition of Hwangki significantly improved the overall palatability of Chungkukjang.
