• The Korean Journal of Food And Nutrition
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• v.10 no.2
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• pp.246-253
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• 1997

This study was conducted to investigate the effect of protein kinds and levels on lipid metabolism in hypercholesterolemia rats. Male Sprague Dawley rats were administrated 1% cholesterol and 0.25% sodium cholate to induce hypercholesterolemia and were fed on diet containing two levels(7, 20%) of casein and soy protein respectively. The rats were sacrified after 5 weeks of feeding periods. Total lipid content in serum was decreased in proportion to level of protein and soy protein was more effective than casein in lipid-lowering effect. Serum triglyceride content was significantly decreased in proportion to level of protein and did not show significance by protein kind. Serum phospholipid content was more significantly decreased in 20% protein groups than that of 7% protein groups. Total cholesterol content in serum was significantly decreased by protein and were decreased in proportion to level of soy protein. Free cholesterol content did not show significance by protein level. The degree of decrease predominated in soy protein groups. Serum HDL-cholesterol content and RL-cholesterol were increased in proportion to level of protein and effect of soy protein was not more significantly than that of casein. Atherogenic index was significantly decreased in proportion to level of protein and soy protein groups were more effective. Serum LDL-, VLDL-cholesterol contents were more significantly decreased in 20% protein groups than that of 7% protein groups. Serum $\beta$-lipoprotein and chylomicrone-cholesterol contents also showed significantly decrease by soy protein.

• Journal of the Korean Home Economics Association
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• v.28 no.4
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• pp.41-50
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• 1990

Soy protein was isolated from Korean soy bean 'Chang ryub' and chemically modified with succinic anhydride. Functionality of the soy protein isolate(SPI), succinylated SPI(SPPI), and PP590(commercial) at various pH were investigated. The mechanical and sensory properties of soy bean curds made from several mixing ratio of succinylated soy bean milk were observed. The solubility of SPI significantly increased with succinylation. The solubility of PP590 was lower than that of SSPI. The solubility of SPPI increased significantly in 0.03M CaCl2 solution. The emulsifying activity of SSPI increased. On the range of pH above pI the emulsifying activity of PP590 was higher than that of SPI. There was no difference in emulsion stability among the groups. The foam expansion capacity of SPPI increased at higher pH than pI but the foam stability decreased significantly above pH 9. Mechanical texture profile analysis revealed the modified soy bean curds had the lower hardniss, chewiness and cohesiveness with increased modification. The mechanical characteristics of modified soy bean curds revealed generalized Maxwell Model of 7-elements or 5-elements. In sensory evaluation, the hardness, the springiness and acceptability of modified soy bean curds were lower significantly than those of control soy bean curd.

• Korean Journal of Human Ecology
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• v.7 no.2
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• pp.149-159
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• 1998

This study was carried out to examine the role soy milk in the preparation of Yukwa, possibility of substitution of soy milk to isolated soy protein and the effect of drying condition of Yukwa dough on the quality of Yukwa for the purpose of standardization of Yukwa preparation process. Although isolated soy protein did not make any particular effect on the gelatinization characteristics of waxy rice flour, soy milk lowered peak viscosity to half of waxy rice flour. The optimum moisture content of dried Yukwa dough was about 25%, and it can be reached by drying at $60^{\circ}C$ under atmosphere pressure for $4{\sim}5$ hours. On the basis of the results of morphological observations, mechanical and sensory measurement of hardness, and sensory test of the internal structure, mouthfeel and overall acceptability, soy milk was more desirable than isolated soy protein for the quality improvement of yukwa.

• Journal of Applied Biological Chemistry
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• v.51 no.3
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• pp.88-94
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• 2008

Three different protein extraction methods-phenol extraction, trichloroacetic acid (TCA) precipitation, and desalting/TCA precipitation-were compared to determine the optimal reproducible high resolution 2-dimensional (2-D) electrophoresis for each chungkugjang, doenjang, and kochujang samples. The soluble proteins from Chungkugjang extracted by phenol were separated with high reproducibility and resolution, and gained 1.75- to 3-fold more protein spots on 2-D gel than those from the other methods. On the contrary, the extracted proteins from doenjang and kochujang treated by desalting/TCA precipitation method showed about 1.5- to 3.3-fold more protein spots on 2-D gel. Using the established methods, the changes in the protein profiles of the fermented soy foods were monitored during the fermentation period by 2-DE. One of the major proteins in soy, $\beta$-conglycinin $\alpha$-subuint, and some proteins with unknown functions were localized on 2-D gel as the protease-resistant proteins throughout the fermentation period of doenjang. Changes in the protein profile monitored by the established methods can provide basic information on unfolding the mechanisms of the generation of biofunctional activity in the fermented soy foods.

• Asian-Australasian Journal of Animal Sciences
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• v.18 no.3
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• pp.326-331
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• 2005

A rumen simulated continuous culture (RSCC) system was used to study the influence of supplementation of the three different types of protein sources such as urea, casein and soy protein on rumen microbial synthesis in terms of rumen microbial synchronization. The urea treatment showed the highest pH value. Ammonia nitrogen concentration was rapidly increased after feeding and not significantly different in the urea treatment (13.53 mg/100 ml). Protozoa numbers were not significantly different for soy protein and casein treatment compared to urea treatments during incubation. The average concentration of total VFA (mMol) was not detected with significant difference among treatments, but iso-butyrate production showed the highest for soy protein treatment among treatments (p<0.001). The lowest concentration in total iso-acids (iso-butyrate and iso-valerate) production was observed in urea treatment. The soy protein treatment showed no significantly change in acetate/propionate. The amounts of dry matter (DM) out flow showed no significant difference among treatments. Organic matter (OM) flow was the highest for urea treatments and the lowest for casein treatment (p<0.03). The nitrogen flow for casein treatment was not significantly different from other treatments. The efficiency of microbial protein synthesis in terms of microbial nitrogen (MN) synthesis (g MN/kg ADOM) digested in the rumen was highest for casein treatment (58.53 g MN/kg ADOM) compared to soy protein and urea (p<0.05). This result suggests that rumen ammonia releasing rate may influence on microbial protein synthesis in the rumen.

• Journal of Nutrition and Health
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• v.37 no.2
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• pp.100-107
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• 2004

This study was performed to evaluate the effect of dietary protein source and sulfur amino acid content on bone metabolism in ra. Thirty male rats (body weight 145$\pm$2g) were divided into three groups. The rats in the first group were fed on casein 20% diet as animal protein source and those in the second group were fed on soy 20% diet as plant protein source. Sulfur amino acid ratio of these group was 1.07:1. The rats in the third group were fed on soy 20% diet and the sulfur amino acid were supplemented with the amount contained as much in the soy 20% diet. All rats were fed on experimental diet and deionized water ad libitum for 9 weeks, The total body, spine, femur bone mineral density and bone mineral content were measured using Dual Energy X-ray Absorptiometry Calcium, phosphate, pyridinoline, creatinine in urine and calcium, phosphate, alkaline phosphatase, osteocalcin in serum were measured. During the experimental period, plant protein (soy protein) group had a lower urinary Ca excretion, urine pyridinoline ＆ crosslinks value and had a higher Ca efficiency in total bone and femur bone mineral density than animal protein (casein) group. There were no significant differences in serum calcium, phosphate, alkaline phosphatase and osteocalcin among the three groups of the rats. The findings from this study demonstrated that plant protein (soy protein) is beneficial of bone mineral density because it had a higher Ca efficiency in total bone and femur bone mineral density than animal protein (casein). However, the supplementation of sulfur amino acid on soy results were consistent with prior studies that dietary sulfur amino acid load had a negative effect on calcium balance. The rats fed sulfur amino acid supplementation diet increased urinary calcium excretion and decreased calcium efficiency for total and femur mineral density. Therefore, dietary protein source and sulfur amino acid content influence bone metabolism. (Korean J Nutrition 37(2): 100-107, 2004)

• Korean Journal of Food Science and Technology
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• v.21 no.1
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• pp.92-99
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• 1989

The soy milk prepared from soy protein concentrate was treated with pretense of various concentrations. Growth and acid production by Lactobacillus acidophilus or L. bulgaricus in soy milk containing partially hydrolyzed protein were investigated. Sensory evaluation of soy yogurt beverages prepared from pretense treated soy milk was also performed. The treatment of soy milk with pretense markedly enhanced acid production by lactic acid bacteria, particularly by L. acidophilus, whereas pH and number of viable cells were not .affected by pretense treatment. Protease treatment of 15 minutes greatly enhanced acid production by lactic acid bacteria, but further treatment up to three hours did not affect the acidity markedly. The sensory evaluation showed that overall acceptability of soy yogurt beverages was slightly improved when soy milk was treated with pretense of 0.1%. The amount of non-protein nitrogen was considerably increased by pretense treatment of 15 minutes and it reached the maximum value by treatment of two hours.

• Journal of Nutrition and Health
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• v.34 no.8
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• pp.833-842
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• 2001

The purpose of this study is to determine the effect of dietary proteins and fats on the hepatic histological changes, membrane stability, and drug-metabolizing enzyme activities during chemically induced rat hepatocarcinogenesis. Weanling Sprague-Dawley rats were fed the diet containing 20% casein or soy protein isolate and 15% perilla or corn oil for 10 weeks. Hepatocarcinogensis was initiated with diethylnitrosamine(DEN), and the rats were fed diets containing 0.02% 2-acetylaminofluorene(AAF) followed by 0.05% phenobarbital (PB). The scores of histological changes were decreased in treated rats fed soy protein diet compared to those find casein diet. Liver weights were significantly increased by AAF and PB treatment in rats fed casein diets in both oil groups. Glucose 6-phosphatase(G6Pase) activities, an index of membrane stability, were significantly reduced by AAF and PB treatment in rats find casein diets, and were lower in casein diet compared to soy protein diet groups. Especially, the activities were the highest in the rats fed soy protein-perilla oil diet. Lipid peroxide values also were increased by AAF and PB treatment in rats fed casein diet. Aniline hydroxylase activities were not influenced by protein and fat sources. Glutathione-dependent enzyme activities were increased by AAF and PB treatment. Linoleic and arachidonic acid content were increased in rats fed corn oil diet, and linolenic and eicosapentaenoic acid contents were increased in rats fed perilla oil diet. Our results suggest that soy protein isolate inhibit the abnormal histological changes in liver, possibly by maintaining the membrane stability during chemically induced rat hepatocarcinogenesis. Soy protein may be protective against the hepatocarcinogenesis induced by chemical carcinogen.

• Korean Journal of Food Science and Technology
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• v.26 no.5
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• pp.603-608
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• 1994

This study was undertaken to find out the effect of phytate on the protein digestibility of various soybean foods, including soy milk, bean curd, curd residue, cheongkukjang, soy sauce, and soy paste. The phytate content of soybean was 2.4%, which decreased to 0.2%, 0.7%, and 0.4% in soy milk, bean curd, and curd residue, respectively, and to 0.2% and 1.0% in soy sauce and soy paste, respectively. The phytate/protein ratio was not correlated with protein digestibility by pepsin whereas the ratio was highly correlated with pancreatin digestibility (p<0.01, r= -0.73). According to SDS-PAGE for the soluble protein fractions, soaked bean showed an alteration in soluble components and bean curd residue exihibited newer low molecular weight bands. Fermented soy products showed no protein band, likely due to degradation.

• Korean journal of food and cookery science
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• v.20 no.3
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• pp.256-264
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• 2004

The effects of irradiation on the functional and structural characteristics of soy protein isolates were studied. Soymilk was irradiated at 1, 5, and l0kGy, after which soy protein isolates were prepared. The functional properties of soy protein isolates were examined including solubility, emulsion capacity and stability, foam capacity and stability, structural properties as represented by SDS-PAGE pattern, and secondary and tertiary structures. The solubility and emulsion capacity were increased by radiation treatment at 1kGy however the values were adversely affected again as dosage was increased above 5kGy. As irradiation dosage increased, an increase of foaming capacity at 1kGy and a decreasing turnover afterwards were also noted in foaming capacity, although the differences were not statistically significant. The SDS-PAGE pattern showed fragmentation and aggregation of protein molecules as affected by irradiation in proportion to the dosage increase. The results of CD and fluorescence spectroscopy revealed increased aperiodic structure contents with the dosage increase. It was assumed that irradiation dosagefrom 5 to l0kGy could initiate minimal denaturation of protein in various foods compared to general heat treatment.