• KOREAN JOURNAL OF CROP SCIENCE
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• v.51 no.spc1
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• pp.174-178
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• 2006

This study was conducted to compare the changes of isoflavone content grown at different planting dates and to determine a relationship between growing periods and isoflavone content, in soybean. A total fifty six soybean varieties, including summer type soybean, Chinese varieties and domestic soybean varieties, were used this experiment. Mean total isoflavone content of domestic soybean varieties was higher than summer type soybean varieties and Chinese varieties. And, the soybean isoflavone content was significantly increased in growth at late planting dates. Soybean isoflavone contents was increased with longer reproductive growth period. While, the relationship between seed weight and isoflavone content showed significantly negative correlation coefficient, -0.57 at Apr. 15, -0.51 at May 15, and -0.38 at Jun. 15, respectively planting dates.

• Journal of Crop Science and Biotechnology
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• v.11 no.1
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• pp.57-62
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• 2008

Isoflavone content in various parts of six soybean cultivars and soybean sprout during germination was analyzed by high performance liquid chromatography. The parts analyzed were seed coat, cotyledon, and axis for seeds and whole sprout, root, hypocotyl, and cotyledon for sprout. Two cultivars, Aga3 which is known to have the smallest seed size and the highest isoflavone content among the Korean soybean cultivars and Pungsannamulkong which is the most widely being used as soy-sprout, were selected for sampling from 1 to 10 days after germination. At the same weight, the order of isoflavone content increased from seed coat to cotyledon to axis. The highest total isoflavone(isoflavone$\times$dry weight) content was observed in the cotyledon and the lowest in the seed coat. The cotyledon of the Aga3 variety had the highest total isoflavone content and the lowest was measured in the Pungsannamulkong variety. The highest total isoflavone content, $10,788{\mu}g/g$, was observed in whole sprouts(cotyledon+hypocotyl+root) on day 7 for Aga3. After day 7, there was a decreasing trend in isoflavone content as the germination period increased. Total isoflavone content in the cotyledon of Aga3 significantly increased after seed germination, whereas the isoflavone content in the cotyledon of Pungsannamulkong decreased. However, total isoflavone content in the root of both varieties increased while isoflavone content in the hypocotyls decreased after seed germination.

• Journal of the Korean Society of Food Science and Nutrition
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• v.26 no.3
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• pp.371-375
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• 1997

The content of genistein and daidzein which were known to be major antioxidative compounds in soybeans were detected by $C_{18}$ reverse phase HPLC. Most of isoflavones in soybeans were detected in the methanol extract but much less amount of isoflavones in the water extract. Among the four different kind of soybeans, the isoflavone content was highest in brown soybean, followed by yellow, small black and black soybean, in the order. These isoflavones were known to be soluble in hot water, which means transfer of isoflavone content was highest in brown soybean, followed by yellow, small black and black soybean, in the order. These isoflavones were known to be soluble in hot water, which means transfer of isoflavones in soy curd into whey during soy curd processing. To identify the change of isoflavone content during processing of soybean curd, soybean curd were made from yellow, brown and black soybean and isoflavone content were determined in each soybean curd, curd residue and whey. Most of soflavones were remained in the whey, it means most of useful antioxidative compounds were wasted. Thus, it is necessary to develop new technology to collect these isoflavones lost during soybean curd processing.

• Korean Journal of Environmental Biology
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• v.21 no.3
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• pp.245-250
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• 2003

Composition of isoflavone in cotyledon and hypocotyl of soybean were detected using HPLC. Optimum conditions for extracting isoflavone from hypocotyl were studied as well. Contents of isoflavone in soybean cotyledon and hypocotyl were 482.5 mg 100 $g^{-1}$ and 3453.3 mg 100 100 $g^{-1}$, respectively. Hypocotyl contained 7~8 times move isoflavone than corresponding cotyledon of the soybean. Malonyl glycoside accounted for move than 70% of the total isoflavone, followed by glycoside, acetyl glycoside, and aglycone. Aqueous ethanol of 60~80% was the most suitable solvent for extracting isoflavone from the hypocotyl. Optimum temperature and time was $90^{\circ}C$, 1hr. Acetic acid, NaCl, and NaOH added to 80% ethanol suppressed extraction yield of the phytochemieal.

• Korean Journal of Community Nutrition
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• v.9 no.5
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• pp.606-614
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• 2004

This study was conducted to investigate the attitude to various soy foods and to estimate dietary isoflavone intake among Korean adolescents. The survey was carried out by self-administered questionnaire with 800 middle and high school students residing in urban and rural areas and 714 questionnaires were collected: resulting in 89% response rate. The dietary isoflavone intake was estimated by food frequency questionnaire developed for rapid assessment of isoflavone intake. Soybean paste, soybean curd, soy milk, bean sprouts and dambuk were recognized as nutritious and healthy food in order. Dambuk got the lowest score in taste and flavor. Bean sprouts, soybean curd and soybean paste were recognized as familiar food in order. Stuffed rice in fried soybean curd got the highest score and Miso soup got the lowest in preference. More than 50% of the subjects consumed soybean paste stew/soup and soybean curd over twice per week and 12.3% of the subjects consumed soybean over once a day. The estimated daily intake of isoflavones ranged from 0 to 227 mg, and the mean daily isoflavone intake of the subjects was 28.1 mg (16.3 mg genistein and 12.0 mg daidzein) whereas the median value of isoflavone intake was 19.7 mg. There was statistically significant relationship among Kyung Gi Do, Chung cheung Do and Seoul residents in their intake of isoflavone. The highest monthly income group consumed isoflavone more than the other groups. These results suggest that Korean adolescent perceived the soybean dishes as high quality foods but they didn't take much because of difficulty to cook or less chance to eat. Nutrition education program is needed to enhance consuming soy foods for prevention of chronic diseases related to dietary isoflavone intake. More detailed information on easy cook method of soy food is also needed.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.41 no.spc1
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• pp.25-45
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• 1996

Soyfoods have potential roles in the prevention and treatment of chronic diseases, most notably cancer, osteoporosis, and heart disease. There is evidence that carcinogenesis are supressed by isolated soybean derived products in vivo such as a protease inhibitor, phytic acid, saponins and isoflavones. It is believed that supplementation of human diets with soybean products markedly reduces human cancer mortality rates. Especially, recent papers recognize the potential benefit of soybean isoflavone components for reducing the risk of various cancers. Isoflavones exhibit a multitude of medicinal effects that influence cell growth and regulation, which may have potential value in the prevention and treatment of cancer. In addition to potential biological effects, soybean isoflavones have the important physiological functions such as the induction of Bradyrizobium japonicum nod genes and the responses of soybean tissues to infection by Phytophthora megasperma as well as biochemical activities such as antifungal and antibacterial actions. Genistin, daidzin, glycitin and their aglycone (genistein, daidzein, glycitein) are the principal isoflavones found in soybean. Malonyl and acetyl forms have also been detected but they are thermally unstable and are usually transformed during the processing in glucoside form. Most soy products, with the exception of soy sauce, alcohol-extracted soy protein concentrate, and soy protein isolate, have total isoflavone concentrations similar to those in the whole soybean. Soybean-containing diets inhibit mammary tumorigenesis in animal models of breast cancer, therefore, it is possible that dietary isoflavones are an important factor accounting for the lower incidence and mortality from breast cancer. Of the total soybean seed isoflavones, $80\~90\%$ were located in cotyledons, with the remainder in the hypocotyls. The hypocotyls had a higher concentrations of isoflavones on a weight basis compared with cotyledons. Isoflavone contents were influenced by genetics, crop years, and growth locations. The effect of crop year had a greater impact on the isoflavone contents than that of location. The climate condition might be the attribution factor to variation in isoflavone contents. Also, while the isoflavone content of cotyledons exhibited large variations in response to high temperature during seed development, hypocotyls showed high concentration in isoflavone content. So, it is concluded that one of the factors affecting isoflavone content in soybean seeds is temperature during seed development. High temperature, especially in maturity stage, causes lower isoflavone content in soybean seed. It is also suggested that there may exist a different mechanism to maintain isoflavone contents between cotyledon and seed hypocotyls. In a conclusion, soy foods may be able to have a significant beneficial impact on public health.

• Food Science and Biotechnology
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• v.16 no.3
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• pp.426-433
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• 2007

We analyzed the isoflavone content of domestic soybeans during steaming, boiling, fermentation, germinating cultivation, fermentation, and soybean curd production. The isoflavone content of the beans was reduced by steaming and boiling, and overall reductions ranging from 16.0 to 65.0% of initial isoflavone values were detected. After 4 days of germinating cultivation, the total isoflavones of Eunhakong increased from 1,341 to $2,017\;{\mu}g/g$ and the total isoflavones of Guinunikong increased from 1,284 to $1,535\;{\mu}g/g$. The isoflavone content of the vinegar beans produced from Hwangkeumkong and Black No.1 increased from 1,877 to $1,956\;{\mu}g/g$, and from 885 to $1,956\;{\mu}g/g$ after 8 days of immersion in 4% acetic acid, respectively. During soybean curd production, significant amounts of isoflavones were lost in the whey (30-31 %) and soybean curd residue (15-20%). Only 37.4% of the isoflavones present in the original soybeans remained in the soybean curd with the hot extraction method, and 50.7% of them with the cold extraction method. Soybean curd prepared with whole soybean method, however, retained 80.7% of the initial isoflavones.

• Journal of Applied Biological Chemistry
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• v.52 no.4
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• pp.163-169
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• 2009

A total of 155 microbial strains were isolated from the Korean traditional soybean paste based on their morphological features on the growth of agar plate. Among the isolated strains, a total of 28 strains were capable of hydrolyzing isoflavone glycoside to isoflavone aglycone efficiently in the soybean paste. Finally, two strains, K123-1 and SI, were selected because of their resistance to 15% NaCl and ability to convert isoflavone glycoside to isoflavone aglycone efficiently during the fermentation of soybean paste. The isolated strains K123-1 and SI were identified to be Pichia guilliermondii and Candida fermentati, respectively, using the partial 26S rDNA sequence analysis and phylogenic analysis. Pichia guilliermondii K123-1 and Candida fermentati SI converted daidzin to daidzein up to 96% and 95%, respectively, and genistin to genistein up to 92% when soybean pastes were fermented at $30^{\circ}C$ for 20 days with a single isolated strain. Pichia guilliermondii K123-1 and Candida fermentati SI were able to grow in the presence of 15% NaCl on both liquid medium and agar plate. We think that Pichia guilliermondii K123-1 and Candida fermentati SI might be one of good candidates for making functional soybean paste because they are isolated from the Korean traditional soybean paste and have a good ability to convert isoflavone glycosides to isoflavone aglycones and a high salt tolerance.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.51 no.1
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• pp.48-52
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• 2006

Naturally occurring soybean isoflavones are known to be influenced by various genetic and environmental conditions. Growth, yield, and isoflavone content were determined in four different cultivars of soybean grown under drained paddy and upland fields. Most of growth characteristics and yield components of four different soybean cultivars harvested in drained paddy field were greater than those in upland field, regardless of cultivar. By means of high performance liquid chromatography, total daidzein and genistein contents of soybean in drained paddy field were increased up to 40 and 35%, respectively, compared with those in drained paddy field. Besides isoflavone contents, the growth and yield of soybean were significantly affected by cultivar and field conditions, indicating the necessity of genetic program for soybean cultivars appropriate to drained paddy field conditions. In conclusion, converting paddy field into upland may effectively improve soybean cropping system, especially in terms of isoflavone increment under paddy field conditions.

• Nutrition Research and Practice
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• v.1 no.3
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• pp.206-211
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• 2007

This study estimated the isoflavone intake level in Koreans using Food Frequency Questionnaire and analyzed related variables. The results showed that the average daily intake of isoflavone in adults was shown as 23.1 mg. The isoflavone intake level at 50 percentile was 16.9 mg ($0{\sim}90\;mg$), and 10% of adults took almost 50 mg of isoflavone a day and 10% took about 5 mg a day. The major food sources for isoflavone in Koreans were in the order of soybean, soybean paste, soy milk, soybean curd (tofu), and bean sprouts; the intake was different depending on age, educational background, occupation, economic standard, and family type. The result showed higher isoflavone intake levels in the group over 30 years old and the highest isoflavone intake in subjects working in farming/fishery, followed by housemakers. According to the differences by families the families with elderly members showed 50% higher isoflavone intake than young families with friends or siblings. Depending on related ecological variables, therefore, various nutrition education programs should be developed for a variety of intakes of soybean foods, along with easy and simple cooking methods as parts of continuous research.