Jong-Hwan Seong

Culture Condition for Listeria monocytogenes 1421 Biofilm Formation and the Effect of Kimchi on Biofilm

Listeria monocytogenes, a fatal food-borne pathogenic bacteria, can form a biofilm on many different supports. The biofilm gives L. monocytogenes more viability and resistance to disinfectants and sterilization procedures. L. monocytogenes formed biofilms on various culture vessels tested in this experiment and showed the maximum amount of biofilm when it was cultured for 4 days at 30℃ in BHI broth. In this study, biofilm formation was stimulated or inhibited by addition of different Kimchi samples. That was not in accordance with the effect of Kimchi on the growth of L. monocytogenes.

Quality Characteristics of Tofu with Added Astringent Persimmon Powder

Quality characteristics of tofu as affected by addition time (before or after coagulant) and the amount (0, 3, 6, and 9%) of astringent persimmon fruit (Diospyros kaki T. cv. Cheongdobansi) powder added were investigated. Yield and sensory acceptability were higher in tofu prepared by adding persimmon before than after adding the coagulant. The yield of tofu with added persimmon was higher than that of the control. The L value of the tofu decreased as the amount of added persimmon increased. Hardness, chewiness, and crispness of tofu made with 6% persimmon were higher than those of the others. DPPH radical scavenging activity tended to increase as persimmon concentration increased but no significant difference was observed between the 3% and 6% added persimmon treatments. A sensory evaluation showed no significant differences in aroma, beany, astringency, and texture. However, the 9% sample had the significantly lowest score for overall acceptability. Thus, astringent persimmon powder (3-6%, before coagulant addition) can be utilized as an additive during tofu processing.

Characteristics of Chungkookjang that Enhance the Flavor and GABA Content in a Mixed Culture of Bacillus subtilis MC31 and Lactobacillus sakei 383

Chungkookjang has several functional properties, such as fibrinolytic activity, anticancer effects, and antioxidant effects. However, children do not like Chungkookjang because of its foul odor. A mixed culture of Bacillus subtilis MC31 and Lactobacillus sakei 383 was used to improve the production of GABA in Chungkookjang and its flavor. Most of the foul odor of Chungkookjang was removed. The slime content and viscosity of Chungkookjang fermented in the mixed culture were similar to those of commercial Chungkookjang when B. subtilis MC31 and Lactobacillus sakei 383 were inoculated in a 1:1 ratio. The maximum GABA content was obtained when Chungkookjang was fermented with B. subtilis MC31 and L. sakei 383, which was fermented at 37℃ for 72 hr. During the period of fermentation, the viable cell number of B. subtilis MC31 reached a peak (log 9.13 CFU/g) at six days, and L. sakei 383 reached a peak (log 6.78 CFU/g) at two days. The moisture, crude ash, crude protein, crude fat, and crude fiber contents were 61.71%, 2.05%, 17.54%, 8.36%, and 1.95%, respectively. The amino-type nitrogen content of Chungkookjang fermented by B. subtilis MC31 and L. sakei 383 was less than Chungkookjang fermented by B. subtilis MC31 alone. The ammonia-type nitrogen and reducing sugar content of the Chungkookjang fermented by B. subtilis MC31 and L. sakei 383 were higher than that of steamed soybean. The glutamic acid and GABA content detected with an amino acid analyzer were 1.40 ㎎/g and 0.47 ㎎/g, respectively. These results suggest that fermentation with B. subtilis MC31 and L. sakei 383 in a 1:1 ratio removes more of the foul odor and increases the GABA content compared with single fermentation.Chungkookjang has several functional properties, such as fibrinolytic activity, anticancer effects, and antioxidant effects. However, children do not like Chungkookjang because of its foul odor. A mixed culture of Bacillus subtilis MC31 and Lactobacillus sakei 383 was used to improve the production of GABA in Chungkookjang and its flavor. Most of the foul odor of Chungkookjang was removed. The slime content and viscosity of Chungkookjang fermented in the mixed culture were similar to those of commercial Chungkookjang when B. subtilis MC31 and Lactobacillus sakei 383 were inoculated in a 1:1 ratio. The maximum GABA content was obtained when Chungkookjang was fermented with B. subtilis MC31 and L. sakei 383, which was fermented at 37°C for 72 hr. During the period of fermentation, the viable cell number of B. subtilis MC31 reached a peak (log 9.13 CFU/g) at six days, and L. sakei 383 reached a peak (log 6.78 CFU/g) at two days. The moisture, crude ash, crude protein, crude fat, and crude fiber contents were 61.71%, 2.05%, 17.54%, 8.36%, and 1.95%, respectively. The amino-type nitrogen content of Chungkookjang fermented by B. subtilis MC31 and L. sakei 383 was less than Chungkookjang fermented by B. subtilis MC31 alone. The ammonia-type nitrogen and reducing sugar content of the Chungkookjang fermented by B. subtilis MC31 and L. sakei 383 were higher than that of steamed soybean. The glutamic acid and GABA content detected with an amino acid analyzer were 1.40 mg/g and 0.47 mg/g, respectively. These results suggest that fermentation with B. subtilis MC31 and L. sakei 383 in a 1:1 ratio removes more of the foul odor and increases the GABA content compared with single fermentation.

Screening and Identification of Soy Curd-Producing Lactic Acid Bacteria

본 연구의 목적은 두유 curd를 형성하는 미생물을 분리하는 것이다. 두유 curd를 형성하는 미생물은 채소를 젖산균으로 발효시킨 전통적인 한국의 음식, 김치로부터 분리하였다. 분리 균주 196개 중 10개의 균주(strain No. 2-2-2, 2-15-2, 2-18-1, 2-19-2, 3-4-1, 3-4-2, 3-8-1, 3-8-3, 3-17-1, 4-39-5)가 단단한 두유 curd를 형성하였고 분자생물학적 생화학적 분석법에 의해 동정되었다. 분리균주로부터 추출한 genomic DNA는 16S rDNA 지역의 PCR 증폭을 위한 주형으로 사용하였다. GenBank 데이터로 16S rDNA 염기서열을 비교한 결과, 분리 균주들은 Leuconostoc mesenteroides group과 Lactobacillus sakei group으로 동정되었다. 두유 curd를 형성하는 균주들의 계통 발생학적 위치와 분류군은 neighbor-joining 방법을 이용하여 확인하였다. 또한, L. mesenteroides group은 생화학적 특성에 의해 L. mesenteroides subsp. dextranicum으로 동정되었다. 하지만 L. sakei group은 생화학적 특성 비교시 다양성을 보여 Lactobacillus sp.로 명명하였다. 【The purpose of this study was to isolate soy curd forming bacterial strains. Soy curd forming bacteria were isolated from Kimchi, a traditional Korean vegetable food that is fermented using lactic acid bacteria. Among 196 bacterial strains, ten isolates (strain No. 2-2-2, 2-15-2, 2-18-1, 2-19-2, 3-4-1, 3-4-2, 3-8-1, 3-8-3, 3-17-1, 4-39-5) formed firm soy curd. The isolated bacterial strains were identified by molecular biological and biochemical analyses. The genomic DNAs extracted from the isolated bacterial strains were used as a template for PCR amplification of 16S rDNA region. By comparing the results of the 16s rDNA sequences with GenBank data, the isolated strains were identified as Leuconostoc mesenteroides group and Lactobacillus sakei group. The phylogenetic position of soy curd forming strains and their related taxa were investigated using neighbor-joining method. L. mesenteroides group was further identified as L. mesenteroides subsp. dextranicum based on biochemical properties. L. sakei group was named Lactobacillus sp., because it showed a variety of biochemical properties.】

Effects of Soluble Collagen Peptides Extract Derived from Mugil cephalus Scale on the Blood Glucose and Lipid Metabolism in Diabetic Rats

This study was conducted to examine the effects of soluble collagen peptides extract supplementation on the improvement of blood glucose, lipid components and enzyme activities in the sera of streptozotocin (STZ, 55 mg/kg BW, IP injection)-induced diabetic rats fed on experimental diets for 5 weeks. The concentrations of blood glucose, total cholesterol, atherosclerotic index, LDL, LDL-cholesterol, free cholesterol, cholesteryl ester ratio, triglycerides (TG) and phospholipids (PL) in serum were remarkably higher in the diabetic group (group SW) and STZ (IP)+collagen peptides extract supplementation group (group SFW) than those in the control group (group CG, basal diet + water). However the concentrations of blood glucose, total cholesterol, atherosclerotic index, LDL, LDL-cholesterol, free cholesterol, cholesteryl ester ratio, TG and PL in serum were lower in the SFW group than in the SW group, whereas the ratio of HDL-cholesterol concentration to total cholesterol and HDL-cholesterol concentration in the SFW group were higher than in the SW group. The activities of alkaline phosphatase (ALP) and aminotransferase (AST, ALT) in serum were lower in the SFW group than in the diabetic SW group. The results shown above suggest that soluble collagen peptides extract supplementation effectively improves blood glucose, lipid compositions and enzyme activities in the sera of STZ induced diabetic rats.

Anti-oxidative Activity of the Extracts from Houttuynia cordata Thunb. Fermented by Lactic Acid Bacteria

This study was performed to evaluate the possibility of application of lactic acid bacteria fermentation to increase the anti-oxidative activity of extracts from Houttuynia cordata Thunb. Houttuynia cordata Thunb. was fermented by two species of lactic acid bacteria, Leuconostoc mesenteroides 4395 and Lactobacillus sakei 383. The anti-oxidative activities of Houttuynia cordata Thunb. extracts were analyzed both before and after fermentation. Anti-oxidative activity was determined by in vitro assays to measure 1,1-di-phenyl-2-picrylhydrazyl (DPPH) scavenging and super oxide dismutase (SOD)-like activities, and by determining total flavonoid and total phenolic compound contents. The extracts of fermented Houttuynia cordata Thunb. had higher anti-oxidative activity than the unfermented control. The DPPH scavenging activity of the extracts after fermentation by Leuconostoc mesenteroides 4395 at 30℃ for 5 days was 71.67±0.52%, and after Lactobacillus sakei 383 fermentation at 35℃ for 5 days was 70.11±0.67%; these activities were both about 20% higher than the control. Increases of about 10 mg GAE/g of total phe-nolic compounds were found in both fermented extracts and both contained about 6 mg quercetin equivalents/g of total flavonoids, compared with 35.90±0.61 mg/g and 21.69±1.52 mg/g in the con-trol, respectively. These results also suggested that fermentation time and temperature were important factors in determining the anti-oxidative effect of extracts from fermented Houttuynia cordata Thunb. These findings should be valuable for the development of medicines or functional foods with anti-oxidative activity.

Isolation and Identification of Antioxidant Compounds of Various Solvents Extracted from Eriobotrya japonica Leaves

To investigate potential medicinal or functional uses of Eriobotrya japonica, this study focused on the isolation and identification of antioxidant compounds from Eriobotrya japonica leaves. Various solvents were extracted from the leaves, and their scavenging effect on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals was measured, in addition to their superoxide dismutase-like activity, polyphenol compounds, and flavonoid content. Ethyl acetate extract exhibited the strongest scavenging effect in a 0.2 mM solution of DPPH (63.24±2.20%, 81.83±2.10%, and 93.15±2.31% in 0.3, 0.7, and 1.0 mg/ml sample concentrations, respectively). The antioxidant effect of the ethyl acetate extract and methanol extract were generally stronger than that of n-hexane extract. The extracts were further purified by repeated silica gel column chromatography. The antioxidant compounds were identified as phytol, β-sitosterol, and (-)-loliolide using GC/MS.

Influences of Silkworm Sericin on the Improvement Actions of Lipid Metabolism in Dyslipidemic Rats

The principal objective of this study was to investigate the effects of silkworm sericin extract supplementation on the improvement of lipid compositions, blood glucose levels and enzyme activities in the serum of dyslipidemic rats. The rats were fed the experimental diet for 5 weeks. Concentrations of total cholesterol, atherosclerotic index, LDL-cholesterol, triglyceride (TG), phospholipid (PL), free cholesterol, cholesteryl ester ratio and blood glucose in serum were higher in the dyslipidemic group (group HCW) and cholesterol-plus-silkworm sericin extract intake group (group HCS) than those in the control group (group BW, basal diet-plus-water). However, the concentrations of total cholesterol, atherosclerotic index, LDL-cholesterol, TG, PL, free cholesterol, cholesteryl ester ratio and blood glucose level in serum were lower in group HCS than those in group HCW. On the other hand, the HDL-cholesterol level and the ratio of HDL-cholesterol to total cholesterol in group HCS were higher than in group HCW. The activities of alkaline phosphatase (ALP) and aminotransferase (AST & ALT) in serum were lower in group HCS than in the dyslipidemic group HCW. From the above results, it was suggested that silkworm sericin extract intake was effective in the prevention and improvement of lipid components, blood glucose level and enzyme activities in the sera of dyslipidemic rats.

Quality comparison of dried slices processed from whole persimmons treated with different deastringency methods

The effects of different deastringency treatments (untreated, carbon dioxide, warm water, or ethanol), before drying on the quality characteristics of dried fruit slices prepared from whole “Cheongdobansi” persimmons were evaluated. L* (lightness) and a* (redness) values of dried slices from warm water- and ethanol-treated groups were higher, respectively, compared to that of dried slices from other groups. Hardness was lower in dried slices from ethanol-treated fruits. Moisture, water activity, soluble solids, titratable acidity, and sensory properties (color, aroma, texture, sweetness, and overall acceptability) of the dried slices from astringency-removed fruits were higher when compared to those of the dried slices from non-treated persimmons. In particular, the dried slices from ethanol-treated fruits showed the highest values for these parameters. Moreover, soluble tannin and DPPH radical scavenging activity decreased by deastringency treatment. Results suggest that ethanol deastringency treatment before drying could be a useful method to improve most quality characteristics, except antioxidative activity, of dried persimmon slices.

Effects of Feral Haw (Crataegus pinnatifida B UNGE ) Seed Extracts on the Antioxidant Activities

Haw(Crataegus pinnatifida Bunge) belongs to the rose family and has beneficial health effects such as anti-obesity and gastroprotective activities. This study compared the antioxidative activities of various solvent extracts from haw. After removing seeds, pulpy was extracted with 70% methanol, 70% ethanol, chloroform :methanol(CM, 2:1, v/v), n-butanol, and ethyl acetate(EA). Total phenol contents were 71.46, 70.41, 47.63, 47.49 and 45.95 ㎎/g in the 70% methanol, 70% ethanol, CM, n-butanol and EA extracts, respectively. Total flavonoid contents of CM and n-butanol extracts were higher compared to other extracts at 1.63 ㎎/g and 1.59 ㎎/g, respectively, whereas EA extract had the lowest flavonoid content at 1.12 ㎎/g. Corresponding to total phenol contents, among NO2 radical scavenging activity, antioxidant activity by β-carotene bleaching assay, and superoxide dismutase(SOD)-like ability, 70% methanol and 70% ethanol extracts showed higher antioxidative activities than the other extracts. However, the lowest activities were n-butanol extract in NO2 radical scavenging activity as well as EA extract in antioxidant activity by β-carotene bleaching assay and SOD-like ability. These results suggest that haw extracts are available as a new natural antioxidant, and its activities are attributed to antioxidant substances such as phenolic compounds and flavonoids.