Food Engineering Progress (산업식품공학)

Korean Society for Industrial Food Engineering (한국산업식품공학회)
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Improvement of Temperature Constancy of Direct Refrigerator for Supercooled Storage

직냉식 냉장고의 과냉각 저장을 위한 항온 특성 개선 연구

  • Kim, Jinse (Department of Agricultural Engineering, National Institute of Agricultural Sciences, RDA) ;
  • Nam, Soyoung (Department of Agricultural Engineering, National Institute of Agricultural Sciences, RDA) ;
  • Jung, Hyun Kyung (Department of Agricultural Engineering, National Institute of Agricultural Sciences, RDA) ;
  • Son, Jae Yong (Department of Agricultural Engineering, National Institute of Agricultural Sciences, RDA) ;
  • Choi, Dong Soo (Department of Agricultural Engineering, National Institute of Agricultural Sciences, RDA) ;
  • Kim, Yong Hoon (Department of Agricultural Engineering, National Institute of Agricultural Sciences, RDA) ;
  • Lee, Soo Jang (Department of Agricultural Engineering, National Institute of Agricultural Sciences, RDA) ;
  • Park, Chun Wan (Department of Agricultural Engineering, National Institute of Agricultural Sciences, RDA) ;
  • Kim, Ha Yoon (Department of Agro-food Resources, National Institute of Agricultural Sciences, RDA) ;
  • Park, Seok Ho (Protected Horticulture Research Institute, National Institute of Horticultural and Herbal Science, RDA)
  • 김진세 (농촌진흥청 국립농업과학원 농업공학부) ;
  • 남소영 (농촌진흥청 국립농업과학원 농업공학부) ;
  • 정현경 (농촌진흥청 국립농업과학원 농업공학부) ;
  • 손재용 (농촌진흥청 국립농업과학원 농업공학부) ;
  • 최동수 (농촌진흥청 국립농업과학원 농업공학부) ;
  • 김용훈 (농촌진흥청 국립농업과학원 농업공학부) ;
  • 이수장 (농촌진흥청 국립농업과학원 농업공학부) ;
  • 박천완 (농촌진흥청 국립농업과학원 농업공학부) ;
  • 김하윤 (농촌진흥청 국립농업과학원 농식품자원부) ;
  • 박석호 (농촌진흥청 시설원예연구소)
  • Received : 2019.10.02
  • Accepted : 2019.11.15
  • Published : 2019.11.30
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Abstract

Commercial direct refrigerators have good energy efficiency, but are difficult to use for supercooled storage due to their large temperature deviation. Placing insulators and conductors inside the refrigerator could reduce these temperature deviations to within 0.3 degrees, allowing for the supercooled storage. The supercooled storage of salted Chinese cabbages during ten weeks was progressed to compare the other low temperature storages. The nucleation temperatures of salted Chinese cabbage were around -2.5℃ and the freezing points were around -0.4℃, so -2℃ was selected for the supercooled storage. The growth rate of lactic acid bacteria and yeast at -2℃ storage was lower than that at 2℃ storage. The reducing sugar was maintained higher due to the growth rate of lactic acid bacteria. The supercooled storage had an effect of delaying the fermentation of the salted Chinese cabbage, which may have the effect of delaying the fermentation of kimchi. This enhancement method of the direct refrigerator was effective for the supercooled storage and would be promising for commercial use.

0℃로 설정 시 최저온도 -9℃ 최고온도 1℃로 온도편차가 10℃ 발생하는 직냉식 냉장고 내부에 단열재와 전도체를 배치하여 온도편차를 목표온도에서 ±0.3℃ 이내로 유지하는 조건을 이론적으로 계산하였고, 상용 판매되는 직냉식 냉장고에 적용하여 효과를 확인하였다. 항온 특성이 개선된 직냉식 냉장고에 -2℃의 과냉각 상태로 절임배추를 저장할 경우 2℃의 저온저장 대비 유산균과 효모의 증식이 완화되었고, 유산균의 먹이가 되는 환원당도 높게 유지되었다. -2℃ 과냉각으로 절임배추를 저장할 때 발효가 지연되는 효과가 나타났기 때문에, 김치를 저장할 경우에도 발효 지연의 효과가 있을 것으로 판단된다. 상용 직냉식 냉장고를 단열재와 전도체의 추가만으로 경제적으로 항온냉장고로 전환이 가능하기 때문에 산업적인 활용이 기대된다.

Keywords

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  1. Freeze-Thaw Study to Minimize the Changes of Lactic Acid Bacteria and Texture of Kimchi vol.24, pp.4, 2019, https://doi.org/10.13050/foodengprog.2020.24.4.235
  2. Supercooling as a potentially improved storage option for commercial kimchi vol.86, pp.3, 2019, https://doi.org/10.1111/1750-3841.15633