김치로부터 분리한 유산균의 특성규명 및 이를 적용한 속성 묵은지 제조

Abstract

Four homo fermentative lactic acid bacteria (LAB) were isolated from Kimchi. Based on morphological and biochemical properties and 16s rRNA gene sequence determination, they were identified as Lactobacillus plantarum AF1, Lactobacillus sakei WJ1, Lactobacillus sakei SC1, and Lactobacillus sakei YY1. Before applying the strains as a starter for kimchi, general characteristics of LAB were investigated. The growth of the LAB was measured; Lb. plantarum AF1 reached stationary phase at 36 h and Lb. sakei WJ1, Lb. sakei SC1 and Lb. sakei YY1 reached stationary phase at 24 h. The effect of initial pH (pH 4, 5, 6, 6.5, 7, 10) and NaCl concentration (0, 1, 3, 5, 7%) of the growth medium on the growth was also observed. They can grow well at 3∼5% of NaCl concentration and pH 5∼pH 7. Lb. plantarum AF1 and Lb. sakei WJ1 was identified as D/L -lactic acid producing strains, respectively. Both Lb. sakei SC1 and Lb. sakei YY1 were identified as L(+) - lactic acid producer. Lb. plantarum AF1 showed about 69% of cholesterol assimilation ability in 24h and 62% in 48h at 30℃. Whereas, Lb. plantarum AF1 showed much higher cholesterol assimilation ability at 37℃; about 82% in 24 h and 97% in 48h. Lb. sakei WJ1 showed 52% of cholesterol reduction in 24 h and 56% in 48 h at 30℃. It showed 43% in 24h and 48% in 48 h at 37℃ and it showed the lowest cholesterol assimilation ability among the four LAB. Lb. sakei SC1 and YY1 strains showed up to 57% of cholesterol reduction in 24 h and 59% in 48h at 30℃. However, their cholesterol assimilaton was lower at 37℃ as 50∼55% in 24 h and 44∼52% in 48 h. Antibacterial activity was found to be active for four LAB against Bacillus subtilis ATCC 6633 and its activity was stable at pH 4.0 and unstable over pH 5.0. These four LAB were used as a starter for kimchi(AF1, WJ1, SC1, and YY1 kimchi). Kimchi was fermented at 15℃ and stored for 240 days at -1℃. The pH of kimchi decreased up to pH 4.0 drastically in fermentation time and showed little change during the storage time. The acidity of kimchi went up rapidly along the low pH. and all 4 strain starter kimchi had lower acidity than general acidity of Mukeunji at the end of the storage. The dominance rate of the used starter in AF1 and WJ1 kimchi was over 90% in 210 days and over 80% in 240 days of storage at -1℃. The dominance rate of the used starter in SC1 and YY1 kimchi kept over 90% in 120 days of storage. But, its dominance rate started to fall down from 180 days and ended with 43∼60%. In spite of their lower dominance rate, SC1 and YY1 kimchi showed more positive evaluation on sensory evaluation than the others. Especially, SC1 kimchi showed soft sweetness and it masked strong sour taste of kimchi. Also, the smell of SC1 kimchi was similar to Mukeunji over 60 days of storage. The color of SC1 kimchi was dark red based yellowish and the texture was crisp enough as Mukeunji. The prepared kimchi with 3% salinity was taken 5 more fermented days to reach pH 4.0 than the starter kimchi. The starter dominance rate of the kimchi was over 90% 120 days of storage but, it started to fall down from 180 days and ended with 43∼51%. SC1 kimchi had more positive assessment on sensory evaluation and showed the similar flavor and taste of Mukeunji when its 60 days of storage. Moreover, the texture of the kimchi was more crispy. However, control kimchi was very sour and showed bad smell when it stored longer time(more than 4 months). Moreover, the control kimchi showed softenity of texture upon long-term storage. The above results, it is considered that Lb. sakei SC1 is the most suitable as a starter for Mukeunji.