Oxalic acid has a nematicidal activity against the root-knot nematode Meloidogyne incognita. High producer of oxalic acid was isolated, and then named as Aspergillus niger F22. Oxalic acid production was investigated under various temperatures from 20 – 33oC and rotational speeds in 5 L jar fermenters. Yield of oxalic acid increased with decreasing temperature. The highest yield was obtained at 23oC, showing the yield of oxalic acid of 8.7 g/L, whereas oxalic acid production was least at 33oC. At 20oC, the yield was lower than that of 23oC. At a rotational speed of 300 rpm, serious oxygen depletion was present from 48 - 72 h, resulting in low productivity of 26.2 mg /L·h. When a rotational speed was set at 600 rpm, dissolved oxygen tension was over 40% and oxalic acid production increased up to approximately 55%. Viscosity during the culture differed with temperatures. Viscosity increased with the increment of temperatures. When A. niger F22 was cultured at 23oC, viscosity was 810 cP, which was favorable for oxalic acid production.

Biological control has been tried for integrated pest management. It is often comparable, safe, and environment-friendly, making itself an alternative for chemical agents. Filamentous microorganisms, i.e., fungi and streptomystes, produce many kinds of useful metabolites, and some of them have been developed as a biocontrol agent. However, they still have a long way because of the concern of manufacturing cost. Therefore, process development was intensively studied to meet cost-effectiveness. Operating conditions of bioreactor, e.g., agitation and aeration, had an effect on biological and physiological responses such as mycelial morphology, oxygen and nutrient transfer. Understanding relationship between operating parameters and microbial responses in terms of growth, substrate and oxygen consumption, and production yield was critical for process development. This study dedicated to build strategies for mass production of biological control agent using aerobic filamentous microorganisms.

본 연구는 다양한 냉동과 해동처리에 따른 계육 가슴살에 natural microflora, 접종된 L. monocytogenes와 C. jejuni 수와 미세구조 변화 구명을 위하여 연구를 수행하였다. −20℃ 송풍식 냉동처리구의 총 호기성 세균과 C. jejuni 수는 4.06 log CFU/g과 4.09 log CFU/g으로 대조구와 비교하여 각각 약 0.7 log CFU/g과 1.0 log CFU/g의 감소를 보였다. 한편, 계육 가슴살 접종된 L. monocytogenes 수는냉동방법과 냉동온도에 따라 유의적인 차이를 보이지 않았다. 4℃와 25℃ 송풍식 해동처리구의 총 호기성 세균수는 3.70 log CFU/g과 4.02 log CFU/g으로 측정되어 대조구와 비교하여 각각 0.72 log CFU/g과 0.40 log CFU/g 감소한 반면 25℃ 유수식 해동처리구의 총 호기성 세균 수는 해동과정에서 균수가 급격히 증가하여 5.78 log CFU/g으로 관찰되었다. 해동 중 C. jejuni 수 변화는 해동방법보다 해동온도에 영향을 받는 것으로 나타났다. 냉동-해동반복 5회 후 총 호기성 세균과 효모 및 곰팡이 수는 감소하여 각각 4.15 log CFU/g과 2.30 log CFU/g을 보였다. 계육 가슴살에 접종된 L. monocytogenes 수는 냉동-해동 반복처리에 유의적인 영향이 없었지만 C. jejuni 수는 냉동-해동 반복 횟수가 증가함에 따라 감소하는 경향을 보였다. 냉동-해동 반복이 증가함에 따라 근섬유 조직을 재 손상시켰으며 특히 냉동-해동 반복 5회 후에는 계육 가슴살 시료의 조직세포 외부뿐만 아니라 내부에서도 공간이 발생하였으며 불균일하게 찢어진 세포가 관찰되었다.

  This paper presents the conceptual framework for estimating and predicting system’s susceptibility to failure as function of condition parameter value which is representing the current status of performance measure using on-line performance reliability.

The quality characteistics and kimchi processing ability of the kimchi cabbage cultivar ‘Cheonjincheongmayup’ (CC) were analyzed and compared with those of the ‘Chunkwang’ (CK) cultivar. The head weight of CC was lower than that of CK, and the head length of CC was larger than that of CK. CC had narrower and longer mid ribs than CK. Furthermore, the head formation index of CC was lower than that of CK. The firmness and soluble solid content were higher in CC than in CK. The salinity of Cheonjincheongmayup kimchi (CCK) was 2.89-3.02%, which was higher than 1.94-2.10% salinity measured in Chunkwang kimchi (CKK). The initial titratable acidity in CCK was higher than that of CKK, but increasd more slowly during storage. CCK was firmer than CKK; lactic acid bacteria in CCK was lower than in CKK initially, but increased more in CKK than in CCK after six weeks of storage. We found that CC was suitable for making Makkimchi because of its long and narrow mid ribs, saltiness, and slow fermentation. CC should be improved as less hot spicy and less hard texture to use a Makkimchi material.

본 연구는 초저온 액체 침지식 급속 냉동으로 동결된 돈육 등심에 적합한 급속 해동방법을 선정하고 과냉각 저장이 냉동-해동 돈육의 미생물학적, 이화학적 및 관능적 품질변화에 미치는 영향을 살펴보았다. 4와 10℃ 송풍식 해동과 4와 10℃유수식 해동은 냉동 돈육 시료가 해동이 완료되는 약 290-750분 소요되었지만 27.12 MHz 라디오파 해동은 약 20분으로 가장 신속하게 돈육을 해동시켜 저장실험에 필요한 냉동 돈육의 급속 해동방법으로 선정하였다. 한편 -1.5--5℃로 24시간 냉각 처리 후 돈육 횡단면의 미세구조 분석 결과, -1.5℃에서 냉각 처리된 시료의 표면과 중심부는 동결에 의한 조직 손상이 발생하지 않았음을 확인하여 -1.5℃를 과냉각 저장 온도로 선정하였다. 저장 중 대조구인 신선육과 비교하여 냉동-해동 처리된 돈육에서 발생한 드립감량은 유의적으로(p<0.05) 높은 경향을 보였지만 -1.5℃ 과냉각 저장이 돈육의 드립감량 증가를 억제하였다. 또한 4와 15℃ 저장과 비교하여 -1.5℃ 과냉각 저장은 대조구와 냉동-해동 처리구의 TVBN과 TBARS 함량 증가, Hunter a* 값 감소와 b* 값 증가를 억제하는 효과를 보였다. 15℃ 저장 4일 후 대조구와 냉동-해동 처리구의 총 호기성 세균수는 9 log CFU/g 이상으로 급격히 증가하였다. 반면 -1.5℃ 저장 10일 후 대조구와 냉동-해동 처리구의 총 호기성 세균수는 각각 5.62와 4.43 log CFU/g으로 관찰되었다. -1.5℃ 저장 10일 동안 대조구와 냉동-해동 처리구의 대장균군과 효모 및 곰팡이 수는 저장 초기 수준으로 유지하거나 다소 감소하였다. 관능평가 결과에 있어서 4와 15℃ 저장에 비해 -1.5℃ 저장한 대조구와 냉동-해동 처리구는 모든 관능평가 항목에서 저장 중 유의적으로 높은 값을 유지하였다(p<0.05). 따라서 라디오파 유전가열 해동은 냉동 돈육 등심의 해동 과정 중 상전이 구간을 빠르게 통과함으로써 급속해동이 가능하였으며 -1.5℃ 과냉각 저장이 냉동-해동 처리 된 돈육에 얼음결정 형성 없이 품질 유지 및 미생물 생장지연에 효과적인 것을 확인하였다.

This study was conducted to determine the potential use for salted Kimchi cabbage and kimchi paste by analyzing the quality characteristic of kimchi prepared with stored them. Salted Kimchi cabbages were packed with the 2% brine and kimchi paste were stored at 4℃ for 8 weeks, respectively. Kimchi prepared at 0 day and kimchi prepared with stored salted Kimchi cabbage and kimchi paste every week were stored at 4℃ for 8 weeks. The salinity and titratable acidity of salted Kimchi cabbage packed with the brine was lower than control. The results of salinity, pH and moisture contents of kimchi paste did not show any significant differences during storage, however, the titratable acidity was increased. In sensory evaluation, salted Kimchi cabbage packed with the brine showed higher score in overall preference than control. Kimchi paste showed 4.9~6.1 score in overall preference during storage. The titratable acidity of kimchi prepared with stored salted Kimchi cabbage and kimchi paste was lower than control. But, the results of sensory evaluation did not show significant difference among treatments. The study suggested that the use of 2% brine is an effective way for extending shelf-life of salted Kimchi cabbage and Kimchi prepared with stored salted Kimchi cabbage and kimchi paste every week is effective to delay the fermentation but no difference in sensory evaluation.