Gliadin in wheat-flour gluten was deamidated by cation-exchange resins in order to enhance the affinity for water; four kinds of cation-exchange resins with functional groups of-N=(CH₂COO^-)₂, -COO^-and-SO₃(Amberlite, IRC718, IRC50, IR120B, and XT1006) were used-The affinity of untreated and deamidated gliadins for water in the region of low water content were evaluated by water sorption measurement and thermodynamic analysis. In addition, the solubility of the samples to water and salt solutions was measured, as an index of affinity of the samples for water in the region of high water content. The gliadin of the largest amount of deamidation was obtained by using IRC 50 which was referred to as CE (COO^-) in this paper, the cation-exchange resin with a functional group -COO^- The degree of deamidation of the gliadins reached about 28% using CE (COO^-) at the optimum conditions (amount: 0.2g/g-solution, treating time: 6hr). Water sorption isotherms of the gliadins were obtained; the amount of sorbed water on the deamidated gliadin was larger than that of the untreated one. The integral Gibbs free energy, ΔG^s, on the basis of solution thermodynamics was calculated. The enhancement of the affinity for water by deamidation was quantitatively evaluated by ΔG^s. The solubility of the deamidated gliadin to water and NaCl solution was higher than that of the untreated one.

View full abstract

Frozen pork meat was thawed under high pressure (100-500MPa) and physicochemical and histological parameters of thawed meat (thawing loss, tenderness, color, drip, ultrastructure, etc.) were compared with those of meat thawed by running water.
Effects on physicochemical properties. The meat drip decreased by high hydrostatic pressurethawing, and the water holding capacity of the meat improved. The discoloration of the meat induced by high pressure-thawing was not recognized by naked eyes up to the pressurization of 200MPa. The meat tenderization was induced during high pressure-thawing. When the frozen pork was pressurized at 200MPa, the most desirable results were obtained. Over 200MPa however, unfavorable changes were brought about by high pressure-thawing.Effects on ultrastructure and myofibrillar proteins. The regular structure of myofibrils was gradually lost with an increase in the pressure applied, and remarkable changes were observed in the meat thawed by pressure above 200MPa.The measurements of the size distribution of the myofibrils prepared from high pressurethawed meats indicated that frequency of distribution centered on a certain length with increasing pressure applied, differing from the progress of the fragmentation as observed in the myofibrils prepared from pressurized meats. The SDS-PAGE analysis showed the progressive solubilisation of α-actinin, troponin T, tropomyosin, and myosin light chain (MLC) in the meat thawed at pressure above 200MPa. These effects caused by high hydrostatic pressure-thawing are applicable to meat processing. lt should be applied to the meat products requiring no long-time heating, such as cured smoked pork, roast beef, tataki, (mince-meat) etc.

View full abstract

The generation mechanisms of pyrazines and phenols, which have already been confirmed to be the key ftavor components of dried bonito, were examined by GC-MS analysis of various volatile compounds in model dried bonito prepared with and without smoking. Pyrazines were generated during heat treatment of boiled bonito meat without smoking, but their amounts and varieties were less than those in ordinary dried bonito. These results suggested that some of unknown substances in smoke could be related to the generation of pyrazines. By the addition of acetol and 2, 3-pentanedione, both of which are known to occur in smoke, the amounts and varieties of pyrazines increased markedly in heated model powder prepared from crushed dried bonito. These findings suggested that acetol and 2, 3-pentanedione react with amino acids or proteins in boiled meat and generate pyrazines. Phenols were not detected in the dried bonito prepared by heating without smoking. Most probably, phenols in dried bonito were mainly derived from smoke. The incubation of the mixture prepared from crushed dried bonito together with smoked cellulose powder, resulted in a decrease in the amounts of furfural, 2-cyclopenten-1-one and 5-methylfurfural. Possibly, these compounds were converted to the non-volatile compounds in the production process of dried bonito.

View full abstract

Yogurt-like food was prepared by use of defatted soybean flour in order to decrease the beany flavor as well as soybean itself as the control. Microwave heating used for preparation of soymilk was effective for protein extraction from"go", soy slurry or defatted soybean flour suspension, in comparison with the conventional heating method by boiling water. Lipoxygenase in soymilk was inactivated at ca. 80°C by either heating method. Trypsin inhibitor activity in soymilk was more decreased by the conventional heating than the microwave heating, and the remaining activity was still nearly 50%. After fermentation of soymilk with a lactic acid bacterium, Streptococcus thermophilus, the trypsin inhibitor activity further decreased to about 30%. For the preparation of more palatable yogurt-like food, soymilk mixed with an equal volume of commercial milk was fermented. The yogurt-like food thus obtained, contained mainly lactic acid as well as citric acid and α-ketoglutaric acid, whose organic acids were detected by HPLC. This food made by using defatted soybean flour was considered as acceptable as food from the sensory evaluation by students panelists, who admitted the improvement of attributes such as beany flavor, taste and overall preference for this food.

View full abstract

Among four tea catechins [(-)-epigallocatechin (EGC), (-)-epicatechin (EC), (-)-epigallocatechin 3-O-gallate (EGCG) and (-)-epicatechin 3-O-gallate (ECG)], gallate type catechins (EGCG and ECG) were specifically adsorbed to isolated soybean protein, which was prepared as water extract of homogenized tempe. The complex of catechins and tempe protein, which easily precipitated in the acidic water solution (pH 4.37), is also expected as a new food material by some bio-activities originated from both catechins and soybean protein. Catechin and tempe protein complex also released the catechin constituents (EGCG, ECG etc) in the extraction with 50% aqueous acetone. Tempe protein was a useful material for the isolation of gallate type catechins from the water extract of tea leaves.

View full abstract

The antibacterial action of chitosan combined with potassium acetate against Escherichia coli IFO 3301 (E. coli) was investigated. The growth of E. coli was more inhibited with chitosan at a higher concentration and more than 3.0mg/l of chitosan suppressed sufficiently its growth at 30°C-incubation for 48h. The antibacterial action of chitosan was more promoted by potassium acetate than any other reagents. Chitosan combined with potassium acetate inhibited the bacterial growth during incubation at various temperatures (20-40°C). The cell-surface hydrophobicity increased by combining chitosan with potassium acetate. Leakage of the UV-absorbing substances from the cells was enhanced in the presence of chitosan and potassium acetate. Furthermore, combined use of chitosan and potassium acetate strongly inhibited respiratory activity. Lastly, glycerol restored the respiratory activity of the injured cells, suggesting reduction in glycerol metabolism in E. coli cells would be one of the combined effects of chitosan and potassium acetate.

View full abstract

Superoxide radical (O₂^-) scavenging activity of fried chips made from purple-fleshed sweet potato was investigated. The twelve chips used in this study were commercially available in Kyushu and Okinawa region. All chips showed O₂^- scavenging activity in the range of 152 to 883units/g expressed as a superoxide dismutase equivalent. Radical scavenging activity of the fried chips was measured by another method using 1, 1-diphenyl-2-picrylhydrazyl (DPPH). DPPH radical scavenging activity of the fried chips highly correlated with O₂^- scavenging activity (r=0.901), indicating the calorimetric assay using DPPH was effective as an alternative to estimate O₂^- scavenging activity. In addition, the HPLC analysis of anthocyanins in the chips reveled that the HPLC elution pattern was subdivided into two groups. As judged by the HPLC pattern, it could be presumed that which cultivar was used in the chips.

View full abstract

The disappearance of sodium nitrite was observed in a pickle solution which was kept in a refrigerator at a particular meat product manufacturing outlet. The purpose of this study was to examine the cause of the disappearance of sodium nitrite added to the pickle solution which was used in the manufacturing process of ham. A strain isolated from this pickle solution was identified as Serratia liquefaciens biovar Clab YD-6. Although the optimum growth temperature for the isolated strain was about 35°C, it was discovered that it could proliferate at 5°C. When the isolated strain was inoculated into the model pickle solution, sodium nitrite decomposed completely after being kept at 10°C for 5 days. However, it was found that S. liquefaciens JCM1245 could not decompose sodium nitrite in the model pickle solution. Furthermore, the addition of preservatives as shelf life expander to the pickle solution prevented the isolated bacteria from decomposing sodium nitrite. Thus, it is concluded that the effective use of preservatives is feasible to prevent the decomposition of sodium nitrite in pickle solution.

View full abstract

We examined the effects of hot-water extracted polysaccharides from either Agaricus blazei or Tricholma giganteum on antitumor activity and NO production. No obvious effects on survival rate and antitumor activity were observed in Tricholma giganteum-administrated male C57 BL/6 mice implanted B16-melanoma cell. Moreover, pulmonary metastasis was observed in a Tricholma giganteum-treated tumor-bearing mice. NO productions from normal mouse peritoneal macrophage were examined. Although polysaccharides from Tricholma giganteum and Agaricus blazei were significantly increased NO production in a dose-dependent manner, those of Tricholma giganteum was lower effect than those of Agaricus blazei. These results suggest that the polysaccharides from Tricholma giganteum have very little or negligible immunological function compared with those from Agaricus blazei.

View full abstract

"Tobiko" (konjac powder)is a by-product formed in the manufacturing process of konnyaku (konjac jelly) and comprises about 45% of dried konnyaku-imo. A chemical analysis is necessary in order to make use of this powder. The content of free amino acids and that of amino acids in protein was determined by an amino acid analyzer to be 1% and 22%, respectively. The fatty acid content determined by GLC analysis after methylation was 1%, palmitic and linoleic acids being the major components, and stearic and oleic acids being the minor components. Glucose, mannose, fructose and saccharose accounted for 4% of the free saccharides. After hydrolysis, a large amount of glucose was confirmed along with the presence of galactose, arabinose and xylose. Some other polysaccharides could be contained except starch and glucomannan. From the chemical composition determined here, we believe that "tobiko" can be used as food material when its characteristic unpleasant smell and irritant taste are removed.

View full abstract