Changes in Microbial and Chemical Composition and Sensory Characteristics of Fermented Soybean Paste, Chungkukjang, by High Dose Gamma Irradiation $(10{\sim}120\;kGy)$

고선량$(10{\sim}120\;kGy)$ 감마선 조사 청국장의 미생물 변화와 화학적 성분과 관능적 특성 변화

  • Ahn, Bo-Sun (Graduate School of Biotechnology, Korea University) ;
  • Lee, Cherl-Ho (Graduate School of Biotechnology, Korea University)
  • 안보선 (고려대학교 생명공학원) ;
  • 이철호 (고려대학교 생명공학원)
  • Published : 2003.04.01

Abstract

Changes in the number of microorganisms, chemical composition, and sensory quality of chungkukjang by gamma-irradiation up to 120 kGy were investigated. The total viable cell counts in chungkukjang irradiated with 10 kGy decreased from $10^9\;CFU/g$ of the control to $10^5\;CFU/g$. Proximate chemical composition and pH of chungkukjang were not much affected by irradiation. Acidity of chungkukjang decreased by irradiation with over 20 kGy. Fatty acid contents of chungkukjang irradiated under 20 kGy were the same as those of the nonirradiated ones. Polyunsaturated fatty acids content, decreased at over 40 kGy. The color and odor of chungkukjang were not significantly affected by irradiation up to 20 kGy. Unpalatable odor (p<0.01), off-flavor (p<0.001), and fish-odor (p<0.001) increased, and brown intensity (p<0.05) and acceptability (p<0.001) decreased at over 20 kGy. Results indicate 20 kGy is sufficient to decrease the microbial count of chungkukjang and prevent decrease in the content of polyunsaturated fatty acids.

시중에서 판매중인 청국장에 Co-60의 감마선을 $0{\sim}120\;kGy$의 선량으로 조사한 후 미생물과 화학적 성분 변화, 특히 지방산 조성 변화를 비교하였다. 조사된 청국장의 미생물 수는 10kGy 조사시 비조사구에 비하여 $10^4$ 정도 감소되었고, $D_{10}$ 값은 3.17 kGy로 나타났다. 일반성분은 조사량이 증가하여도 변화가 없는 것으로 나타났으며 pH는 조사구와 비조사구간에 차이가 없었으나, 산도는 조사구가 비조사구에 비하여 감소하는 경향을 보였다. 청국장의 지방상 조성은 대두나 증자대두와 유사하게 12종이 확인되었다. 청국장의 주요 지방산 양은 대두나 증자대두에 비해 oleic acid와 palmitic acid는 적고, linoleic acid와 linolenic acid는 더 많은 것으로 나타났다. 감마선 조사 청국장의 지방산 조성은 조사선량 20 kGy 조사구는 비조사구와 크게 다르지 않았으나 40 kGy 이상의 고선량 조사에서 linoleic acid와 linolenic acid가 감소하였다. 감마선 조사 청국장을 관능검사한 결과 비조사구에 비하여 갈색도(p<0.05), 꼬린내(p<0.01), 생선비린내(p<0.001), 이취(p<0.001), 수용성(p<0.001) 항목이 유의적 차이를 보여 감마선 조사 선량이 커질수록 비조사구와 색이나 냄새에서 차이가 있는 것으로 나타났다. 안전성을 고려하여 1, 5, 10 kGy 조사구를 대상으로 실시한 맛 관능검사의 결과는 비조사구와 비슷한 수준이었다. 이상의 결과를 종합하여 볼 때 청국장의 멸균을 위해서는 40 kGy 이상의 조사량이 필요하나, $20{\sim}40\;kGy$ 정도의 조사 선량으로 미생물 수를 $10^2$이하로 충분히 낮출 수 있고 다가불포화지방산의 감소를 방지하면서 청국장 고유의 관능적 특성을 유지할 수 있을 것으로 판단되었다.

Keywords

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