A laboratory study was made to develop a method of extending storage-life of kimchi in a mechanically compressed form.
In the first part, sensory characteristics of kimchi undergoing fermentation at 5℃ from raw state to the inediable were described and a 9-point hedonic scale was developed by a sensory evaluation team consisting of 6 trained panel mambers. Employing the 9-point hedonic scale as a sensory analysis tool, the pattern of quality changes of kimchi during fermentation at 5˚, 10˚, 20˚ and 30℃ was determined in terms of changes in total lactic acid bacterial counts, titratable acidity, $p^H$, reducing sugar contents and sensory scores.
In the second part, the kimchi of the highest sensory score was mechanically compressed to separate the liquor from the kimchi and the possibility for storage-life extension was investigated under each separate category; the mechanically compressed kimchi treated with 0.1% K-sorbate, 0.05% Na-benzoate and 0.05% dehydroacetic acid(DHA) and packaged into a nylon 6 flexible pouches was stored at 20℃ and their fermentation pattern was compared with un-compressed or compressed, but untreated with the preservatives in order to determine the possible benefit of the mechanical compression combined with preservative treatments in extending storage-life of kimchi. The separated kimchi liquor was heat treated to determine the minimum heat treatment necessary for arriving at commercial sterility. The compressed kimchi and liquor were then to be recombined immediately before serving.
On the other hand, 10% glycerol was mixed with each preservative as its carrying vehicle and the mixture treated with the compressed kimchi in order to further extend storage-life.
The results obtained from this study are as following:
1. The organoleptic characteristics of kimchi throughout entire fermentation spectrum could be classified into five different phase: (a) The raw phase; (b) incipient ripening phase; (c) well-ripened phase; (d) over-ripening phase and (e) inedible phase. A 9-point hedonic scale sensory evaluation scheme was developed for judging kimchi quality with the boarderline of acceptability(5 points) being assigned to the raw as well as to the kimchi of a strong acid taste having no sweety flavor tone in the overripening phase.
2. The length of edible period was inversely related to the temperature at which kimchi was fermented. Thus at 5℃ the edible period lasted approximately 50 days with 17 days of the well-ripened phase(from the 10th to 26th day); at 10℃, 25days with 6 days of the well-ripened phase (from the 5th to 10th day);at 20℃, 8 days with 5 days of the well-ripened phase(from the 2nd to 6th day); and at 30℃, only 3days with 24 hours of the well-ripened phase (from the 24th to 48th hour). The total acidity content of kimchi corresponding to the well-ripened phase was highest when fermented at 30℃ (approximately 1% at 30℃, 0.6% at 20℃, 0.7% at 10℃ and 0.6% at 5℃).
3. The optimum compression conditions for yielding a compressed form of kimchi still acceptable as fresh kimchi organoleptically were determined to be 1 ton/㎠ for 10 minutes. Compression of the well-ripened kimchi under the conditions yielded approximately an equal weight of compressed kimchi and liquor, indicating a volume reduction by one-half. Over 90% of total microflora present in the kimchi prior to compression were found in the liquor portion.
4. Mechanical compression alone did not prove to be effective for extending storage-life when tested at 10˚ and 20℃. Treating the compressed kimchi with 0.1% K-sorbate, 0.05% Na-benzoate and 0.05% DHA was not effective also.
5. The compressed kimchi treated with 10% glycerol containing the same preservatives, however, proved to be effective. In all three cases, approximately a 2-fold storage-life extension could be realized at 20℃ as compared to the compressed kimchi samples.
1. 김치 발효 양상을 막 버무린때 부터 양념 맛과 김치 맛이 없는 때 까지의 lag period 급격히 미생물이 $10^8$ 이상 성장하며 산도가 0.5% 이하가 되는 맛이 드는 시기 조화된 시코롬한 김치 맛과 화려하고 환하며 산도가 0.6 -0.7% 정도 되는 맛있는 단계, pH가 조금씩 저하하고 당이 급격히 감소되며산도가 높아져 신맛이 나는 과숙되는 단계, 초같이 시며 산과 pH 가 일정한평형을 유지하는 과숙된 단계, 김치 조직 연화와 산막 효모 발생 그리고 색이 퇴색되어 먹을 수 없는 못 먹는 단계로 6구분 하였다.
2. 김치 발효 속도는 맛있는 때가 30 ℃에서 28시간, 20 ℃에서 48시간, 10 ℃에서 4.5일, 5 ℃에서 14일 후로 또는 저장기간은 30 ℃에서 30일간, 20 ℃에서 8일간, 10 ℃에서 25일간, 5 ℃에서 50일 전후로 온도에 따라 각기 달랐다.
3. phase change 에 따른 종합적 관능 검사를 하고 이에 따라 김치 발효 현상은 9-point hedonic scale로 표시하여 객관화를 시도 하였다.
4. 2차 가공을 목적으로 압축 김치를 만들어 저장성을 본 결과는 압축 김치가 yeast 와 mold 의 공격으로 보통 김치 보다 맛과 함께 저열 하였다.
5. 적숙기의 김치에 방부제의 사용은 potassium sorbate가 처음에 산생성을 억제시킨 외에 전부 발효 억제보다는 계속적인 산생성을 촉진 시켜으며, dehydro acetic acid 등은 쏘는 맛까지 있었다.
6. 압축김치에 10% glycerol을 첨가 하였을 때 저장기간이 높았으나 미약한발효가 계속 되었으며, glycerol과 방부제의 병용은 방부제의 antimycotic 효과와 함께 공지에 방치한 상태에서도 상당히 보존성이 있어 맛으로 보아 보통김치보다 저장기간을 2배 이상 연장 시킬수 있었다.
7. 맛의 변화를 적게 하고 유산균 성장을 억제시키는 김치국물의 살균조건은 60 ℃에서 20여이상 30분 이하가 적당 하였다.
