Yong-Suk Kim

Development of a RAPD-PCR method for identification of Bacillus species isolated from Cheonggukjang.

A RAPD-PCR (Randomly Amplified Polymorphic DNA-PCR) method was developed for rapid identification of Bacillus species, especially B. subtilis, B. licheniformis, and B. amyloliquefaciens, the most frequently isolated organisms from fermented soy foods such as Cheonggukjang, a Korean traditional food. A RAPD-PCR using a 10-mer (S-30) produced species specific bands reproducibly. All B. subtilis strains tested produced common bands of 0.5 and 0.88 kb in size. All B. amyloliquefaciens strains generated 1.1 and 1.5 kb bands together with 0.5 kb fragment whereas B. licheniformis strains produced 1.25, 1.70, and 1.9 kb bands with an occasional 0.5 kb band. Using the RAPD-PCR protocol, six bacilli strains isolated from Cheonggukjang were identified to the species level, which was difficult by 16S rRNA gene and recA gene sequencing for some isolates. The 0.5 kb fragment, the major band for B. subtilis strains, was an internal part of a ytcP gene encoding a hypothetical ABC-type transporter. A B. subtilis species specific primer pair was designed based on ytcP sequences and PCR using the primer pair produced a 0.46 kb fragment only from B. subtilis strains.

Quality Characteristics of Doenjang (Soybean Paste) Prepared with Germinated Regular Soybean and Black Soybean

Department of Functional Crops, NICS, RDAAbstract Three types of doenjang were prepared with regular soybean, germinated regular soybean, and a mixture ofgerminated regular and black soybean. After 90 days of fermentation, pH, moisture, and salt contents of doenjang were6.01±0.01-6.72±0.01, 53.78±0.22-57.99±0.11, and 14.17±0.06-15.03±0.21%, respectively, showing slight differencesaccording to soybean germination. Amylase and protease activity of doenjang changed similarly during fermentation in allsamples. Amino-type nitrogen and free amino acid content of germinated black soybean doenjang after 90 days offermentation were 1256.21±1.86 and 994.46 mg%, respectively, which were higher than those of other samples. A sensoryevaluation of germinated regular soybean doenjang showed the highest scores for color, taste, and overall acceptability.These results suggest that high sensory quality doenjang can be prepared using germinated regular soybean and a mixtureof germinated regular soybean and black soybean.Keywords: doenjang, soybean, black soybean, germination, enzyme activity

Effects of Germination Time of Soybeans on Quality Characteristics of Cheonggukjang Fermented with an Isolated Bacterial Strain

Sunchang CountyAbstract To investigate the effects of soybean germination time on the quality of cheonggukjang, the physicochemicalcharacteristics and enzyme activities of cheonggukjang during fermentation were compared. B. subtilis SCD 115035 strainisolated from traditional cheonggukjang was selected for making cheonggukjang. Germinated (12-h) soybean-cheonggukjang produced the highest amount of viscous substance (13.22%) after 48 h of fermentation, and the contentswere inversely proportional to the germination time of the soybeans. The acidic- and neutral-protease activities ofungerminated soybean-cheonggukjang were higher than those of germinated soybean-cheonggukjang. The amino nitrogencontent of ungerminated soybean-cheonggukjang was the highest (436.93 mg%) at 48 h of fermentation, and its contentwas similar to that of 12-h germinated soybean-cheonggukjang. However, the total isoflavone content of 36-h germinatedsoybean-cheonggukjang was the highest after 72 h of fermentation, and its content was higher than those of cheonggukjangmade from soybeans germinated for 0, 12, and 24 h.Keywords: cheonggukjang, soybean, germination, enzyme activity, isoflavone

Degradation characteristics of proteins in cheonggukjang (fermented unsalted soybean paste) prepared with various soybean cultivars

In order to select the most ideal soybean cultivars for producing cheonggukjang, the protein degradation characteristics of cheonggukjangs prepared with 30 different soybean cultivars were compared. Cheonggukjang prepared with ‘Nampung’ (18.00±0.28%) and ‘Sohwang’ (17.91±0.63%) soybeans showed the highest contents of viscous substances. Acidic-protease activity was highest (590.24±2.92 μg/mL) in cheonggukjang prepared with small ‘Pungsannalmul’ soybeans. Neutral-protease activity was highest (528.13±3.11 and 527.36±0.44 μg/mL, respectively) in cheonggukjang prepared with ‘Singi’ and ‘Nampung’ soybeans. Cheonggukjang prepared with ‘Wonkwang’ and ‘Sohwang’ soybeans had amino-type nitrogen contents of 780.50±2.92 and 729.95±1.07 mg%, respectively. Glutamic acid, which is a major component of viscous substances, was also detected. Although total free amino acid levels in cheonggukjang prepared with ‘Daewon’ and ‘Wonkwang’ soybeans measured 2,551.21 and 2,340.02 mg%, respectively, cheonggukjang prepared with black soybeans exhibited low levels of total free amino acids. Therefore, based on protein degradation characteristics, large ‘Daewon’ soybeans and small ‘Wonkwang’ soybeans were the most suitable for producing cheonggukjang.

Biological activities of cheonggukjang prepared with several soybean cultivars

To select proper soybean cultivars for producing functional cheonggukjang, a comparison was made of the physiological activities of different cheonggukjang prepared with 30 different soybean cultivars. The isoflavone content was highest in the cheonggukjang made from ‘Daepung’ soybeans at 208.75 mg%. In general, the contents of glycone types (and derivatives) of isoflavone, specifically daidzin, glycitin, genistin, and malonylgenistin, were higher than that of aglycone types. The polyphenol contents ranged from 30.62 to 80.32 mg%. The DPPH radical scavenging activity and superoxide dismutase (SOD)-like activity of the cheonggukjang made from yellow soybeans had a higher activity than those of black soybeans. Although there are no consistent tendencies in the functional activity of cheonggukjang according to soybean color and size, the antioxidative activity is highest in the cheonggukjang made of yellow soybeans. Additionally, the fibrinolytic and inhibitory activities against angiotensin I-converting enzyme are highest in the cheonggukjang made of black soybeans. From these results, it can be concluded that the DPPH free radical scavenging activity and SOD-like activity in cheonggukjang depends on the phenolic compound content in soybean.

Biological activities of fermented soybean paste (Doenjang) prepared using germinated soybeans and germinated black soybeans during fermentation

To produce doenjang with enhanced biological activities, doenjang was prepared by fermenting regular soybeans (RS), germinated soybeans (GS), and germinated black soybeans (GBS) for 90 days. The isoflavone contents in GS and GBS-doenjang were slightly higher than in RS-doenjang in the early stage of fermentation. The DPPH radical scavenging activity of GBS-doenjang was highest at 70.00% after 30 days of fermentation. The angiotensin-converting enzyme (ACE) inhibiting effects increased as the fermentation period progressed, and were significantly (p<0.05) higher in GBS-doenjang (58.69%) than in other preparations after 75 days of fermentation. The greatest fibrinolytic activities were 127.59 and 100.00% in nontreated GBS-doenjang and GBS-doenjang treated for 30 min at 55°C, respectively. There were significant (p<0.05) correlations between the total isoflavone content and the antioxidant activity (0.779) and between the isoflavone content and the ACE activity-inhibiting effects (0.669). GBS-doenjang exhibited greater antioxidant activities, ACE-inhibition, and fibrinolytic activities than RS and GS-doenjang.

Analytical Method of Silicon Dioxide in Health Functional Food Products using ICP-OES

건강기능식품에서 이산화규소 분석 방법을 확립하기 위하여 산(불산과 붕산)분해를 이용한 ICP-OES 방법을 수행하였다. 이 방법의 검출한계와 정량한계는 각각 0.07 mg/L, 0.20 mg/L 이었다. 검량선은 0.2~20.0 mg/L의 농도범위에서 우수한 직선성(

An analysis method for determining residual hexane in health functional food products using static headspace gas chromatography

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Effect of various additives on reduction of unpleasant odor and inhibition of Bacillus cereus growth in cheonggukjang

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Antioxidant Activities of Ethanol Extracts from Different Parts of the Black Raspberry (Rubus occidentalis) Obtained Using Ultra-sonication

A method for analyzing the contents of residual hexane in health functional food products was developed. The dissolving solvents in the health functional food products and the internal standard selected were N,N-dimethylacetamide and heptane, respectively. The analysis conditions for headspace-gas chromatography/flame ionization detection (HS-GC/FID) and headspace-gas chromatography/mass spectrometry (HS-GC/MS) were determined as 18 mL of headspace volume, 100°C of headspace oven temperature, and 30 min of equilibration time; a Durabond (DB)-624 column was selected for this analysis. To validate this method, which applies N,N-dimethylacetamide as a dissolving solvent, the limit of detection and limit of quantification (LOQ) values based on the HS-GC/FID and HS-GC/MS analyses results were found to be 0.10, 0.29 and 0.16, 0.47 mg/L, respectively. The recoveries and coefficient of variation (CV) obtained by HS-GC/MS were 96.39–119.86% and 0.04–1.25%, respectively, better than those obtained by HS-GC/FID. By applying the HS-GC/MS method, it was possible to analyze the content of the residual hexane in 60 different types of health functional food products.