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

• Korean Journal of Food Science and Technology
• /
• v.9 no.3
• /
• pp.190-193
• /
• 1977

In our previous report (Korean J. Food Sci. and Technol., 9, 123, 1977) we have studied the functional properties of soy protein isolates prepared from defatted soybean meal. For the practical application of the data described, beef patties substituted with SPI, and imitatied ice cream were prepared and sensory evaluations were carried out. The sensory analyses indicated that the beef patties substituted with gelated SPI to 30% have no detectable difference to the control at the significant level of 0.01. The imitation of ice cream whose milk-solid-not-fat was substituted with soy protein isolates showed the same texture as the control. Flavor of ice cream, however, has significant difference to the control due to beany-off flavor. Therefore removal of beany-off flavor is required for the substitution in ice cream.

• Korean journal of food and cookery science
• /
• v.20 no.6 s.84
• /
• pp.658-666
• /
• 2004

In order to develop and commercialize high quality frozen soy yogurt, the effects of industrial proteases and commercial mixed cultures were examined on the functional properties and the sensory attributes of frozen soy yogurt. For quality improvement, soy protein isolates were primarily hydrolyzed by either Flavourzyme or Neurtrase, industrial Proteases, to reduce the beany flavor and increase the functional properties of the protein. The viable cell count of lactic acid bacteria was higher in the soy protein hydrolysates than whenuntreated. ABT-5 (L. acidophilus, Bifidobacterium lactis, and S. thermophilus) resulted in higher acid tolerance, bile acid tolerance and melt-down percent values than those with YC-X11 (Lactobacillus bulgaricus and Streptococci thermophilus). The overrun of frozen soy yogurt was improved by both Flavourzyme $(193.3\%)$ and Neurtrase $(156.7\%)$ treatments. With regard to thesensory characteristics, Flavourzyme improved the beany flavor, astringency taste, mouth feel and overall quality of frozen soy yogurts fermented with ABT-5. Further studies onproduct formulation will be needed to commercialize the frozen soy yogurt for the market.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.51 no.2
• /
• pp.148-153
• /
• 2006

Effects of ${\alpha}$-chymotrypsin modification on degree of hydrolysis (DH), solubility, emulsifying capacity and thermal aggregation of laboratory-purified soy protein isolate (SPI) using a lipoxygenase-defected soybean (Jinpum-kong) and commercial soy protein isolate (Supro 500E) were compared. SPIs were hydrolyzed by ${\alpha}$-chymotrypsin at pH 7.8 and $37^{\circ}C$ for 30 min. DHs of Supro 500E and Jinpum-kong SPI were increased by ${\alpha}$-chymotrypsin modification, and DH of Supro 500E was higher than that of Jinpum-kong SPI. DH of ${\alpha}$-chymotrypsin treated Jinpum-kong SPI was similar with untreated Supro 500E and DH of treated Supro 500E was the highest. Solubility, emulsifying capacity and thermal aggregation of SPIs were increased by ${\alpha}$-chymotrypsin modification, and these changes were highly related to changes in DH. Functional properties of Supro 500E were higher than Jinpum-kong SPI in both of untreated and ${\alpha}$-chymotrypsin treated SPIs.

• Korean journal of food and cookery science
• /
• v.21 no.2 s.86
• /
• pp.217-224
• /
• 2005

The storage characteristics of frozen soy yogurt prepared with hydrolyzed soy protein isolates were evaluated. In order to facilitate lactic fermentation bacteria grow and produce lactic acid as fast rate as possible, soy protein isolate(SPI) was hydrolyzed using two kinds of proteases; bromelain and a-chymotrypsin. The cultural systems employed thereafter for lactic fermentations were Bifidobacterium bifidum or B. bifidum and Lactobacillus bulgaricus. The viable cell counts, normal- and bile acid tolerances from the mixed cultures of B. bifidum and L. bulgaricus decreased sharply during the initial first 3 days of frozen storage and then showed a gradual decrease thereafter. Melt-down percent of the all frozen products have been favorably affected as was shown by less melting at raised testing temperature during 28 days of frozen storage except for the initial 3 days during which a minor change has been observed. Among the various volatile flavor components, the contents of acetaldehyde, acetone, diacetyl and methanol generally increased during the frozen storage. In sensory test, the frozen soy yogurt prepared with a-chymotrypsin and mixed culture of B. bifidum and L. bulgaricus was the most desirable, the highest scores in sourness, bitterness and mouthfeel.

• Korean Journal of Food Science and Technology
• /
• v.23 no.3
• /
• pp.286-290
• /
• 1991

Phytic acid known as an antinutritional facfor was studied for its effect on the solubility and digestibility of high-phytate and low-phytate soy protein isolates (SPI) obtained by two different methods of pH adjustment. Phytic acid content was 2.48% in high-phytate SPI and 0.72% in low-phytate SPI. Solubility of soy proteins was higher in low-phytate SPI than in high-phytate SPI at all pH values tested and it was lowered by adding more phytic acid to result in precipitation of the proteins. The inhibitory effect of phytic acid toward pepsin digestion of SPI increased by the increasing amount of phytic acid added and its effect was slightly higher in high-phytate SPI than in low-phytate SPI.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.45 no.9
• /
• pp.1285-1292
• /
• 2016

Changes in surface hydrophobicity of soy protein isolate (SPI), which plays an important role in the functional characteristics of protein, were measured according to various SPI concentrations, pH levels, electrolytes concentrations, and alginate molecular weights by using 1-anilino-8-naphthalene sulfonic acid as a fluorescent probe. SPI surface hydrophobicity decreased as SPI concentrations increased. SPI surface hydrophobicity reached a maximum at pH 7.0. SPI surface hydrophobicity rapidly increased as the NaCl concentration of SPI solution increased up to 100 mM, and showed no large increases above 100 mM. However, SPI surface hydrophobicity radically decreased until the $CaCl_2$ concentration reached 50 mM and revealed no large variations above 50 mM. A similar trend was exhibited in the case of $MgCl_2$. As both the concentration and molecular weight of sodium alginate increased, SPI surface hydrophobicity decreased. The increasing rate of SPI surface hydrophobicity decreased as the molecular weight of sodium alginate increased.

• Korean Journal of Food Science and Technology
• /
• v.24 no.3
• /
• pp.204-208
• /
• 1992

This study was carried out to develop a practical enzyme-linked immunosorbent assay(ELISA) for the determination of soy protein in processed meat products as a preliminary study. The titer of antiserum raised in rabbit by injection of SDS-treated whole buffer extract(WBE) from isolates soy protein(ISP) was above 1:10,000 in indirect ELISA. When the SDS concentration was higher than 0.03% the antibody-antigen reaction was inhibited significantly. However, the antibody-antigen reaction inhibition was not observed when the SDS concentration was less than 0.02%. The antibodies used in this experiment also reacted with renatured antigen after removing SDS by dialysis, though not better than with SDS-denatured antigen(immunogen). The calibration curve with $100\;{\mu}g/100\;ml$ of sensitivity was obtained in indirect competitive ELISA.

• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
• /
• 2001.06a
• /
• pp.1156-1156
• /
• 2001

This work aimed to prove the feasibility of NIR spectroscopy to detect vegetable protein isolates (soy, pea and wheat) in milk powder. Two hundred and thirty-nine samples of genuine and adulterated milk powder (NIZO, Ede, NL) were analysed by NIRS using an InfraAlyzer 500 (Bran+Luebbe). NIR spectra were collected at room temperature, and data were processed by using Sesame Software (Bran+Luebbe). Separated calibrations for each non-milk protein added, in the range of 0-5%, were calculated. NIR data were processed by using Sesame Software (Bran+Luebbe). Prediction and validation were made by using a set of samples not included into the calibration set. The best calibrations were obtained by the PLSR. The type of data pre-treatment (normalisation, 1$\^$st/ derivative, etc..) was chosen to optimize the calibration parameters. NIRS technique was able to predict with good accuracy the percentage of each vegetable protein added to milk powder (soy: R$^2$ 0.994, SEE 0.193, SEcv 0.301, RMSEPall 0.148; pea: R$^2$ 0.997, SEE 0.1498, SEcv 0.207, RMSEPall 0.148, wheat: R$^2$ 0.997, SEE 0.1418, SEcv 0.335, RMSEPall 0.149). Prediction results were compared to those obtained using other two techniques: capillary electrophoresis and competitive ELISA. On the basis of the known true values of non-vegetable protein contents, the NIRS was able to determine more accurately than the other two techniques the percentage of adulteration in the analysed samples.

• Fisheries and Aquatic Sciences
• /
• v.14 no.4
• /
• pp.347-354
• /
• 2011

Aeromonas salmonicida is an important fish pathogen commonly associated with furunculosis in salmonids. Typical A. salmonicida strains have the surface virulence A-layer protein, a major virulence determinant encoded by the vapA gene. In this study, 880 chum salmon Oncorhynchus keta were collected from the east coast of Korea during 2006-2011, including 560 wild adults and 320 artificially hatched fry pools, and the presence of typical A. salmonicida was examined by PCR using the typical A. salmonicida-specific vapA gene primers. The results demonstrated that 34.5% of the samples (304/880 samples) were PCR positive, implying that a typical A. salmonicida infection is highly prevalent among chum salmon in Korea. Twenty typical A. salmonicida isolates were recovered based on their brown pigmentation on Trypticase Soy Agar (TSA) plates, which indicates the existence of the A-layer protein. Further biochemical analyses with the four randomly selected typical A. salmonicida isolates revealed some variations in their amino acid decarboxylation and carbohydrate fermentation activity. A phylogenetic analysis based on the entire vapA gene sequence suggested that the A. salmonicida isolates from chum salmon were clustered with those isolated from Atlantic salmon in Europe. Further study is needed to resolve such an interesting relationship in detail.