Korean Journal of Food Science and Technology (한국식품과학회지)

Korean Society of Food Science and Technology (한국식품과학회)
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Changes in Microflora and Enzyme Activities of Cheonggukjang Prepared with Germinated Soybeans during Fermentation

발아대두 청국장의 발효 중 미생물과 효소활성도의 변화

  • Oh, Hoon-Il (Department of Food Science and Technology, Sejong University) ;
  • Eom, Sang-Mi (Department of Food Science and Technology, Sejong University)
  • 오훈일 (세종대학교 식품공학과) ;
  • 엄상미 (세종대학교 식품공학과)
  • Published : 2008.02.28
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Abstract

This study was carried out to investigate the changes in microflora, enzyme activity and sensory quality of four kinds of cheonggukjang during fermentation. Three different kinds of cheonggukjang were prepared with germinated soybeans using rice straw, Bacillus natto, B. natto plus Aspergillus oryzae, and the last one was prepared with non-germinated soybeans using rice straw. The pH values of cheonggukjang prepared with germinated or non-germinated soybeans increased up to 36 hr of fermentation and then decreased. The number of bacteria and molds increased significantly up to 24 hr of fermentation and then leveled off during fermentation. Acidic and neutral protease activities of all cheonggukjang continuously increased significantly during fermentation. ${\alpha}$- and ${\beta}$-Amylase activities of cheonggukjang decreased slightly during fermentation except cheonggukjang prepared with germinated soybeans using the mixed culture. The number of microflora, protease and ${\alpha}$-amylase activities were highest in cheonggukjang prepared with germinated soybeans using B. natto plus A. oryzae. The results of the sensory evaluation revealed that for overall acceptability, the cheonggukjang prepared with germinated soybeans using B. natto plus A. oryzae was similar to the cheonggukjang prepared with non-germinated soybeans using rice straw.

대두를 $25^{\circ}C$에서 48시간 발아시킨 콩을 원료로 볏짚, Bacillus natto, B. natto와 Aspergillus oryzae 혼합균을 접종하여 제조한 청국장과 비발아콩 볏짚으로 제조한 청국장의 발효 중 미생물 및 효소활성도 변화를 조사하고 관능평가를 실시하였다. 4종류의 청국장 모두 발효가 진행되면서 pH가 서서히 증가하여 최대 pH를 보인 이후 다시 감소하여 발효 72시간에는 비발아콩 볏짚 청국장>발아콩 볏짚 청국장>혼합균주를 이용한 발아콩 청국장>B.natto를 이용한 발아콩 청국장 순으로 높은 pH를 나타내었다. 청국장 발효 중 미생물의 변화는 세균의 경우 모든 청국장에서 발효가 진행됨에 따라 급격히 증가하여 발효 12시간에 $10^7-10^8$ CFU/g를 나타내었으나 그 이후에는 발효시간에 따라 큰 변화를 나타내지 않았다. 곰팡이 수는 B. natto를 접종한 발아콩 청국장을 제외하고는 발효 48-60시간에 $10^8$ CFU/g로 최대값을 나타낸 이후 감소하였으며, B. natto를 접종한 청국장은 발효시간에 따라 지속적으로 증가하여 발효 72시간에 $10^8$ CFU/g을 나타내었다. Protease활성은 발효가 진행됨에 따라 acidic과 neutral protease 활성 모두 증가하였으며 neutral protease의 활성도가 acidic protease에 비해 높았다. 이는 청국장 발효과정 중 neutral protease의 최적 활성 pH인 7.0 부근으로 청국장의 pH가 변화했기 때문인 것으로 사료된다. ${\alpha}$-Amylase 활성도의 경우 혼합균주를 이용한 발아콩 청국장을 제외하고는 발효가 진행됨에 따라 전반적으로 감소하는 경향을 보였으며, ${\beta}$-amylase 활성도는 혼합균주를 이용한 발아콩 청국장을 제외한 다른 3 종류의 청국장에서 발효 12시간에 최대활성을 나나타낸 이후 감소하였다. 관능검사 결과 냄새와 향기에 있어서 비발아콩 볏짚 청국장의 선호도가 높은 것으로 나타났으나 전체적인 기호도는 B. natto와 A. oryzae를 이용한 발아콩 청국장과 비발아콩 볏짚 청국장이 유사하게 높게 나타났다.

Keywords

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