Changes in Microbiological and General Quality Characteristics of Gamma Irradiated Kanjang and Shoyu

감마선을 조사한 간장의 미생물 및 일반품질 특성

The effect of gamma-irradiation on the microbiological and general qualities of Kanjang (fermented soy sauce, Korean type) and Shoyu (fermented soy sauce, Japanese type) was studied. Samples were prepared, irradiated at 5, 10 and 20 kGy, and then stored at $25^{\circ}C$ for 18 weeks. The results showed that the Bacillus spp. was inactivated by 3 log cycles with the irradiation dose of 10 kGy and the number of Bacillus cells that survived from 10 to 20 kGy of gamma irradiation was decreased gradually during storage. Yeasts and Lactobacillus were nearly eliminated at 5 to 10 kGy of irradiation. The $D_{10}$ values of Bacillus, yeast and Lactobacillus in Shoyu were 2.67 kGy, 0.81 kGy and 1.30 kGy, in Kanjang were 2.75 kGy, 0.99 kGy and 1.47 kGy, respectively. The general quality of gamma irradiated Shoyu and Kanjang, such as total nitrogen, amino nitrogen, protease activity and pH were more stable than that of control during storage periods. Decolorization was observed just after irradiation, but the color was recovered during storage. The sensory evaluations showed that irradiated samples were more acceptable. Therefore, it was considered that gamma irradiation was effective for maintaining better quality of Shoyu and Kanjang during storage.

간장의 미생물 관점에서의 보존성 향상 및 살균을 목적으로 양조간장과 한식간장에 5, 10, 20 kGy의 선량으로 감마선을 조사하고 상온에 18주간 보존하면서 간장의 미생물 및 일반품질 변화를 조사하였다. 간장의 Bacillus는 10kGy의 감마선 조사에 의하여 5 log cycle 이상 제거되었으며 효모와 젖산균은 5 kGy의 선량에서도 완전 사멸에 가까운 살균효과를 보였다. 간장 보존 중의 일반품질 평가 요소인 총질소, 아미노산성질소, 중성단백분해효소 활성, pH등은 감마선 조사에 의하여 영향을 받지 않았고 보존기간 중에도 안정적인 품질 수준을 유지하였다. 간장의 갈색도는 감마선 조사 직후에 낮아졌으나 보존 2주 이후부터는 비조사구의 수준으로 환원되었다. 감마선을 조사한 간장은 관능적으로도 안정된 품질 수준을 유지하였다. 따라서 감마선 조사는 간장의 보존?유통 및 가공에서 위생화 및 미생물적, 이화학적, 관능적 품질을 유지하는데 유용한 방법이 될 수 있을 것으로 평가되었다.