Hydrolysis of egg yolk protein in mayonnaise was investigated using emulsion consisting of egg yolk, vinegar and oil (egg yolk emulsion), and commercial products. The free tyrosine content in trichloroacetic acid filtrates increased in each preservation condition of the egg yolk emulsion to give 20μg/ml after 3 hours at 40°C, 50μg/ml after 3 days at room temperature and also 50μg/ml after 3 weeks at 5°C, respectively. According to SDS-PAGE analysis, the patterns changed with preservation time, and especially the protein of about 200kDa decreased and the protein of about 165kDa newly appeared. Aspartic proteinase activity in egg yolk almost remained in the egg yolk emulsion. In two fresh mayonnaise obtained directly from a factory at different times, the hydrolysis of egg yolk protein was confirmed during preservation similar to that in the egg yolk emulsion though the extent of hydrolysis was different between the two samples. Compared with the egg yolk emulsion, aspartic proteinase activity per a gram of mayonnaise in four kinds of mayonnaise purchased from markets ranged from 0.7 to 2.3 times. The SDS-PAGE patterns of the four samples were similar to those of the egg yolk emulsion. The results showed that egg yolk protein in mayonnaise was hydrolyzed by egg yolk aspartic proteinase during preservation.

View full abstract

Superoxide anion-scavenging activity (SOSA) of alkaline protease hydrolysate from sardine meat (A-1) was measured by colorimetry using water-soluble tetrazolium salt (WST-1). A-1 showed low activity with IC₅₀ value of 9.21mg powder/ml. The hydrolysate was separated into F-1-F-6 on an ODS column. The most active fraction (F-4) was fractionated by ion exchange chromatography on SP-Sephadex C-25 into three active fractions (1/SP-3/SP). The first fraction, 1/SP, showed the most potent activity (IC₅₀=4.11mg powder/ml). By elution with a stepwise gradient of acetonitrile containing 0.1% TFA on Sep-pak plus C18 cartridge, A/SE (IC₅₀=2.12mg powder/ml) and B/SE (IC₅₀=7.14mg powder/ml) were obtained from 1/SP. A/SE was extracted with water or 20% acetonitrile. A/SE W, the water extract, showed high SOSA with an IC₅₀ value of 0.51mg powder/ml. The amino acid analysis of each active fraction indicated that five amino acid residues (Leu, Phe, Pro, Met, Tyr) played important roles in the activity. Moreover, it was suggested that the potent scavenger contained few histidine residue.

View full abstract

Thermal conductivity of three kinds of liquid food (reconstituted milk, skim milk, whey) of concentrations between 10% and 40% (w/w) was measured at five temperatures ranging from 10°C to 50°C. The effects of temperature and concentration on the thermal conductivity of sample solution were investigated. The transient heat probe method using twin probe was used for the determination of the thermal conductivity. Therefore, thermal conductivity of these sample could be represented as a function of both temperature and concentration. In addition, observed values were compared with the calculated values from the typical several kinds of the heat conduction model. Therefore, heat conduction model assumed to have distributed four components, i. e. protein, fat, carbohydrate, and ash, in water was most suitable one to predict thermal conductivity of sample solution.

View full abstract

We reported previously that fresh herbs belong to Labiatae, especially in oregano contained very high 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity and polyphenol compounds. DPPH radical scavenging activity of fresh herbs was positively correlated with polyphenol content. DPPH radical scavenging activity and superoxide anion (O₂^-) scavenging activity measured by nitrite method of oregano fresh leaves were 13400μmol ascorbic acid (AsA) eq./100g fr. wt. and 7380μmol AsA eq./100g fr. wt., respectively. Among more than 20 peaks detected by high performance liquid chromatography (HPLC) in 80% ethanol extract of oregano leaves, rosmarinic acid, protocatechuic acid and caffeic acid were identified by retention time of HPLC and ultraviolet absorption spectrum. DPPH radical and O₂^- scavenging activities in boiled leaves were approximately 1.3 times higher than those in fresh leaves. Although the amounts of rosmarinic acid, protocatechuic acid and caffeic acid were increased after boiling, prominently increased phenolic compound in boiled leaves was a compound of peak 1. This was identified as 3-(3, 4-dihydroxyphenyl) lactic acid by ultraviolet absorption spectrum, nuclear magnetic resonance spectrum and mass spectrum. Identified 4 phenolic acids contributed approximately 55% of the DPPH radical scavenging activity and approximately 30-40% of the O₂^- scavenging activity of both of fresh and boiled leaves of oregano.

View full abstract

Japanese traditional red turnip pickles (Akakabu-tsuke) required for a long period for matured products. As aging proceeded, lactic acid bacteria make good taste and color of Akakabu-tsuke. Two strains of lactic acid bacteria, Leuconostoc sp. D-133 and Lactobacillus casei L-14 as mixed-starter culture for Akakabu-tsuke were selected for investigation. The results obtained were summarized as follows, (1) The optimum condition of preparation of red turnip pickles was fermentation at 18°C for 6 days and aging at 10°C for 1 month on 0°C for 5 months. (2) Under the condion red turnip pickles with good taste and without uncomfortable flavor (diacetyl, acetoin) was produced. (3) Addition of these strains suppressed unavoidable coloring of Akakabu-tsuke for a long period.

View full abstract

The effectiveness of electrolyzed water from tap water on productivity of a functional peptide, which is derived from soybean protein by hydrolysis with a protease from Aspergillus oryzae, was examined. After mixing soybean powder (1g) with a small amount of the protease (2mg), the sample was added into three different water samples (10ml), then incubated at 40°C. Water samples are neutral water (NW) after removing chlorine from tap water, electrolyzed cathode water (ECW) and electrolyzed anode water (EAW) obtained from the NW. A low-molecular weight peptide was produced in any water samples, however, the ECW sample contained the most abundant peptide. The peptide eliminated the DPPH radical very effectively. The concentration of residual SH group, retarding the oxidation of the soybean casein, of the peptide in the ECW and in the EAW samples, were 1.8 and 1.3 times higher than that in the NW, respectively. These results suggested that the ECW sample is suitable for producing a peptide with a high oxidation resistant ability. And the ECW sample raised the activities of the alkaline protease and the neutral protease, while the EAW sample activated the acidic protease. The mechanism raising protease activity in those electrolyzed water samples was also examined. The pH, ionic concentration and oxidation-reduction potential are suggested to be responsible concertedly with other properties of the water.

View full abstract

Heat soluble proteins in whey fraction of soybean seed were analyzed by SDS-PAGE and two-dimensional polyacrylamide gel electrophoresis. From the SDS-PAGE pattern, 26 kDa dehydrin appeared to be the most abundant polypeptide in the fraction. Beside the 26 kDa dehydrin, several unidentified polypeptides were recognized as major polypeptides in the two-dimensional electrophoresis gel. Cryoprotective activity of total soluble protein and heat-soluble whey proteins on freeze/thaw inactivation of lactate dehydrogenase were estimated. CP₅₀ value for heat-soluble whey fraction was estimated to be 15.8μg/ml, while that of total protein fraction was 355μg/ml.

View full abstract

The study has been made to find the effect of water soluble vitamin K₂ complex from Okara fermented with Bacillus natto on the bone of growing rat maintained on a low calcium containing diet by checking calcium content, bone density and breaking properties of the femur. Serum vitamin K₂ and calcium level, the breaking strength and bone density of femur bone of rat on diet with water soluble vitamin K₂ complex increased in comparison with that of rat on diet without water soluble vitamin K₂ complex. These results suggest that water soluble vitamin K₂ complex can be closely related to the mineralization of femur bone.

View full abstract

The inhibitory effect on inflammatory cytokine production of citrus fruits harvested in Kagoshima prefecture was examined in mouse macrophage cell line. Extracts (with water and ethanol) of the all citrus from Kagoshima had inhibitory effect on production of tumor necrosis factor. In Tankan, the extract of immature peel was more effective than that of mature one. We tried to identify inhibitory component in Tankan. After HPLC fractionation, mass spectrometry was applied for identification of the compound. As a result, it was estimated that the main compound was nobiletin. We detected another more potent inhibitory fraction in the Tankan extract.

View full abstract