• Korean Journal of Food Science and Technology
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• v.36 no.1
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• pp.38-43
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• 2004

Effects of heat treatment on functional properties of soy protein were examined. Soy protein isolate (SPI) was prepared from Korean soybean varieties, Manli and Taekwang, subjected to heat treatment at $60^{\circ}C$ for 30, 60, 90, and 120 min. pH-solubility results of SPI showed typical U-shape profiles with minimum solubility at pH 4-5 of isoelectric points of soy proteins, longer heat treatments showing slightly higher solubility. Water absorption, emulsifying activity, emulsion stability, and emulsion capacity of SPI increased, while oil absorption decreased, with heating time in Manli variety. Manli and Taekwang showed the highest emulsion capacities after 90-and 60-min heat treatments, respectively. Foam expansion of all SPIs increased with heating time up to 90 min. Texture profile analysis showed heat treatment up to 90 min significantly increased hardness, adhesiveness, springiness, gumminess, and chewiness, whereas significantly decreased cohesiveness of SPI gels (p<0.05).

• Korean Journal of Food Science and Technology
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• v.16 no.2
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• pp.211-217
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• 1984

To study affinity of proteolytic enzymes to soy proteins, the physicochemical and functional properties of enzymatically modified protein products, kinetic parameters and degree of hydrolysis were measured using trypsin, alcalase (serine type protease) and pronase. Bacterial alcalase and pronase showed much greater affinity to soy protein than animal intestinal trypsin. This effect was very significant when unheated soy isolate was used as a substrate. Specific activities of these enzymes decreased with the increment of substrate concentration (over 2.0%, w/v) when heat denatured soy protein was used as a substrate. However, the decrease in specific activity was negligible at substrate concentrations lower than 2.0%. Polyacrylamide gel electrophoretic results showed that the pattern of 2S protein band changed distinctly in alcalase hydrolysis as compared with those of trypsin and pronase. Protein solubilities of alcalase and pronase hydrolyzates increased by 25-30%, at their pI (pH 5.0) over the control. Virtually no change was observed in solubility by trypsin hydrolysis. Heat coagulability and calcium-tolerance of the protein increased by enzymatic hydrolysis. No clear tendency, however, was observed for emulsion properties, foam expansion and the amount of free -SH groups. The enzyme treatment considerably decreased foam stability.

• Korean Journal of Food Science and Technology
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• v.29 no.6
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• pp.1236-1240
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• 1997

The crude extract of Morus alba Linne bark which showed strong antimicrobial activity on Listeria monocytogenes was fractionated by some solvents and applied column chromatography for purification of active component. By silica gel column chromatography, active fraction (F-5') was purely isolated and confirmed their strong bactericidal effect on Listeria monocytogenes tested at level of 100 and 300 ppm in tryptic soy broth. The cell wall observed by SEM was abnormal after treatment of F-5'.

• Korean Journal of Food Science and Technology
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• v.36 no.4
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• pp.568-573
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• 2004

Effects of dry heating and pH on pasting, thermal, and textural properties of corn starch containing soy protein isolate (SPI) were investigated. Samples were prepared by drying corn starch dispersions containing 3% SPI at $40^{\circ}C$ (unheated sample) or additionally heating dried mixtures at $130^{\circ}C$ (heated sample). Pasting properties of starch samples and textural properties of starch gels were measured using Rapid Visco-Analyzer (RVA) and Texture Analyzer (TA), respectively. Effects of SPI addition and dry heating on retrogradation and microstructure of gel samples were investigated using DSC and SEM, respectively. Pasting viscosity of dry-heated samples was significantly higher than that of unheated samples, and at pH 8 compared to pH 6. Dry-heat treatment decreased fracture stress and strain of starch gels containing SPI. No significant effects of dry-heat treatment and pH were observed on retrogradation of starch gels. Addition of SPI retarded starch retrogradation and modified starch gel properties with increased nutritional value. Dry-heat treatment with SPI could be possible method for starch modification.

• Korean journal of food and cookery science
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• v.9 no.4
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• pp.261-265
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• 1993

For the purpose of supplying the information to improve the acceptability of soy paste as the condi-ment, the changes of peptide were determined. The results were as follows; Average peptide length were decreased. It was 102 at 0 day, 15 at 10 day and 4.1 at 180 day. Peptide fraction were the same as in 60 day and 180 day. Low molecular weight peptide were not changed greatly during fermention. Peptide identified in 180 day fermentation were Ala-Ser, Gly-Glu, Glu-Ser, Asp-Glu, Asp- Tyr, Asp-Ala-Ser, Ala-Ser-Glu, Glu-Ser-Ala, and Ala-Lys-Met. In the characteristics of bitter peptide in 180 day fermentation, soy paste itself didn't show bitter taste', solvent extration fraction I'showed bitter taste. After gel chromatography, fraction I, fraction II and fraction III were obtained and fraction II were bitter peptide of low molecular weight. After gel chromatography', solvent extration fraction 2'(water extration) were divided into fraction IV, V, VI,VII and VIII. Fraction IV, V and VI showed bitter taste. Amino acids composition of the fractions showing bitter taste were like that; fr. 1: Glu- (Asp, Pro, Val, lie or Leu)-Met fr. II Pro-(Glu, Val, Phe)-lle or Leu fr. IV: Glu-(Asp, Ala, Tyr, Leu of lie)-Phe fr. V: Ala-(Met, Glu, Pro)-lle or Leu fr. VI: Asp-(Phe, Ser, fly)-Val.

• Korean Journal of Food Science and Technology
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• v.39 no.4
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• pp.438-446
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• 2007

The fermented soybean product, cheonggukjang, is favored by many people, partly due to its bio-functional ingredients. Since the fermentation process of cheonggukjang is mediated by enzymes, including proteases, produced by microbes, analysis of the proteome profile changes in cheonggukjang during fermentation would provide us with valuable information for fermentation optimization, as well as a better understanding of the formation mechanisms of the bio-functional substances. The soluble proteins from cheonggukjang were prepared by a phenol/chloroform extraction method, in order to remove interfering molecules for high resolution 2-D gel analysis. Proteomic analysis of the cheonggukjang different fermentation periods suggested that most of the soluble soy proteins were degraded into smaller forms within 20hr, and many microbial proteins, such as mucilage proteins, dominated the soluble protein fraction. The proteomic profile of cheonggukjang was very different from natto, in terms of the 2-D gel protein profile. Among the separated protein spots on the 2-D gels, 50 proteins from each gel were analyzed by MALDI-TOF MS and PMF for protein identification. Due to database limitations with regard to soy proteins and microbial proteins, identification of the changed proteins during fermentation was restricted to 9 proteins for cheonggukjang and 15 for natto. From de novo sequencing of the proteins by a tandem MS/MS, as well as by database searches using BLASTP, a limited number of proteins were identified with low reliability. However, the 2-D gel analysis of proteins, including protein preparation methods, remains a valuable tool to analyze complex mixtures of proteins entirely. Also, for intensive mass spectrometric analysis, it is also advisable to focus on a few of the interestingly changed proteins in cheonggukjang.

• Microbiology and Biotechnology Letters
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• v.31 no.3
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• pp.284-291
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• 2003

Bacillus amyloliquefaciens K-42, which produces strongly a fibrinolytic enzyme, Was isolated from Ganjang, a traditional Korean soy sauce. The fibrinolytic enzyme was purified to homogeneity by ammonium sulfate fractionation, ion-exchange chromatography on DEAE-Sephadex A-50, gel chromatography on Sephadex G-100, and gel chromatography on Sephadex G-75 of the culture filtrate of Bacillus amyloliquefaciens K42. The purified enzyme showed the specific activity of 59.4 units per milligram, which was increased by 17.1 fold over the culture broth. And the molecular weight of purified fibrinolytic enzyme was confirmed to be about 45,000 Dalton by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The enzyme activity was relatively stable at pH 4.0-10.0 and the optimum pH was 8.0. The activity of the purified enzyme was increased by $Mg^{2+}$ , Cu$^{2+}$ but the enzyme was totally inhibited by $Ba^{2+}$ $Hg^{2+}$ In addition, the enzyme activity was potently inhibited by EDTA, EGTA and CDTA. It was concluded that the purified enzyme was a metalloprotease. And Km value was 2.03 mg/ml to fibrin.

• Journal of the Korean Society of Food Science and Nutrition
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• v.21 no.6
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• pp.681-685
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• 1992

Low molecular weight RNA(LMW RNA : 5S rRNA and tRNAs, <150 nucleotides) profiles of several bacteriocin production lactic acid bacteria from pig meats and reference lactic acid bacteria were generated on 10% denaturing polyacrylamide gel electrophoresis. Data evaluation including three molecular weight markers enabled the calculation of relative nucleotide units(RNU) for every band. Gels profiles and RNU evaluations were effective for identification of lactic acid bacteria species. LMW RNA profiles of lactic acid bacteria showed no variation in dependence on APT(All Purpose Tryptone Broth), TSB(Tryptic Soy Broth), MRS(Lactobacilli MRS Broth) different cultural medium.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.35 no.6
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• pp.627-632
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• 2002

This study was investigated the changes of gel properties about pH, color and water holding capacity at various hydration time and temperature of food-grade additives (BPP: bovine plasma protein, DEW: dried egg white, SPI: soy protein isolate). The changes of rheological properties were checked about hydration time and temperature. Hydration time and temperature affected pH value, hydration decreased pH of SPI and DEW. The BPP was not influenced at hydration time and temperature. Some Hydration condition increased jelly strength of food-grade additive, but SPI did not form a gel at all hydration condition. Hydration increased lightness of food-protein.

• Korean Journal of Food Science and Technology
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• v.27 no.3
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• pp.336-341
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• 1995

Effect on alginate, pectin and Ca salts on textural properties of whole soybean gel(soygel) was investigated. The soygel was prepared by addition of sodium alginate, pectin and Ca salts into whole soy flour(300 mesh, WSF) suspension followed by through mixing. Addition of sodium alginate or pectin into WSF suspension significantly increased the hardness, adhesiveness and cohesiveness of the gel. The most uniform gel was obtained by $12{\sim}15%$ addition of sodium alginate or pectin, while their mixture rather decreased the textural properties. Sensory evaluation by ranking test for the gels showed that 12% sodium alginate and 0.125g $CaSO_4/g$ WSF produced the most desirable gel in terms of elasticity, uniformity, smoothness and total acceptability, followed by 12% sodium alginate and 0.12g Ca $gluconate-CaSO_4$(50 : 50). From the results, the optimal preparative conditions for soygel were suspension of WSF in 10 times of water(v/w), addition of 12% sodium alginate(w/w of WSF) and 12.5% $CaSO_4$ or Ca $gluconate-CaSO_4$(50 : 50) into WSF suspension followed by gel formation at $4^{\circ}C$.