Masaki Okuda

National Research Institute of Brewing, Edo, Tōkyō, Japan

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Publications (18)26.11 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Ferulic and p-coumaric acids were analyzed in 50 rice (Oryza sativa L.) samples from 32 cultivars harvested in Japan. In brown rice, ferulic and p-coumaric acid levels ranged from 309 to 607 mg/kg and from 49 to 100 mg/kg, respectively. In 70% polished rice, ferulic and p-coumaric acid levels ranged from 27 to 103 mg/kg and from 0.4 to 3.5 mg/kg, respectively. Ratios of average phenolic acid levels in the 70% polished rice to the brown rice were 13.9% for ferulic acid and 1.9% for p-coumaric acid. The ferulic acid level was highly correlated between brown and 70% polished rice (R = 0.815; P < 0.01), but there was no clear correlation for p-coumaric acid. Phenolic acid levels in the 70% polished rice did not show any clear correlations between the analytical index measurements for sake brewing suitability (weight of 1,000 grains, water absorption, digestibility, crude protein, and potassium content). Phenolic acid levels in the 70% polished rice directly affected levels in the rice koji enzyme digest. The results indicated that phenolic acid levels in sake were affected by the levels in ingredient rice grains, which may then influence the sensory quality of sake.
    Cereal Chemistry 01/2014; 91(1):45-49. DOI:10.1094/CCHEM-06-13-0118-R · 1.06 Impact Factor
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    ABSTRACT: Using rice grains contaminated with radioactive cesium ((134)Cs and (137)Cs) that was released by the Fukushima Daiichi Nuclear Power Plant Accident in March of 2011, we investigated the behaviors of the radioactive cesium and potassium (total K and (40)K) during sake brewing. Cesiumis a congener of K, and yeast cells have the ability to take up Cs using known K transporters. During rice polishing, the concentrations of radioactive Cs and K in the polished rice grains decreased gradually until a milling ratio (polished rice weight/brown rice weight) of 70% was reached. No significant changes were observed below this milling ratio. Sake was brewed on a small scale using the 70% polished rice. The transfer ratio of radioactive Cs to sake and to the sake cake was significantly different than the ratio of K. Approximately 36% and 23% of radioactive Cs in the polished rice was transferred to the sake and sake cake, respectively; however, 40% was removed by washing and steeping the rice grains. On the other hand, 25% and 40% of K in the polished rice was recovered in the sake and sake cake, respectively, and 35% was removed by washing and steeping the rice grains. From the present results, the concentration of radioactive Cs in sake would be 4 Bq/kg fresh weight, which is well below the regulation values (100 Bq/kg), even using brown rice containing 100 Bq/kg of radioactive Cs.
    Journal of Bioscience and Bioengineering 04/2013; DOI:10.1016/j.jbiosc.2013.03.001 · 1.79 Impact Factor
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    ABSTRACT: The food-processing transfer parameters of radioactive and stable cesium and radioactive potassium were determined from grapes to wine. The concentration of cesium in the pomace was higher than that in juice, as was the case of potassium. During white and ros wine fermentation, cesium concentration did not change significantly and potassium concentration decreased. These results suggest that the absorbance of cesium by yeast is much lower than that of potassium in the winemaking environment. The food-processing retention factors (Fr, content in wine/content in grape) of radiocesium and stable cesium for red wine were generally higher than those for white wine, reflecting the yields of wine and the extraction of cesium during maceration.
    American Journal of Enology and Viticulture 02/2013; 65(1):143-147. DOI:10.5344/ajev.2013.13079 · 1.63 Impact Factor
  • Food Science and Technology Research 01/2013; 19(4):705-709. DOI:10.3136/fstr.19.705 · 0.36 Impact Factor
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    ABSTRACT: Possible contamination by radioactive cesium (Cs), released by the Fukushima Daiichi Nuclear Plant Accident in Japan on March 2011, has been a matter of concern with respect to Japanese sake made from rice grains cultivated in affected fields. In this study, the behavior of stable (133)Cs, which is a useful analogue for predicting the behavior of radioactive Cs, was investigated in the production of sake using rice grains harvested in Japan in 2010. The concentration of stable (133)Cs in the polished rice grains decreased gradually with decreasing milling ratios until a ratio of 70% was reached, and below that point, it did not change significantly. The (133)Cs concentration in the 70% polished rice was approximately 20% of that found in brown rice. The sake was brewed on a small scale using 70% polished rice, and the transfer of (133)Cs from rice to sake was examined. Approximately 30-40% of (133)Cs in the 70% polished rice was removed during the washing and the steeping of the rice grains, and approximately 40% of the (133)Cs in the 70% polished rice was transferred to the sake. If the radioactive Cs species behaves similarly, these results suggest that brown rice containing 100 Bq/kg radioactivity of Cs would generate 70% polished rice grains containing 20 Bq/kg and that the sake brewed from these grains would contain 3-5 Bq/kg.
    Journal of Bioscience and Bioengineering 07/2012; 114(6). DOI:10.1016/j.jbiosc.2012.07.003 · 1.79 Impact Factor
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    ABSTRACT: The taste-active hydrophobic compounds in a charcoal-untreated sake sample were subjected to a taste dilution analysis (TDA). All of the high-TDA factor fractions showed a bitter or astringent taste in common, but their taste characters were different. The taste-active compounds of the high-TDA factor fractions were purified by taste-guided fractionation, using RP-HPLC and an instrumental analysis. From each of the seven fractions, ferulic acid, ethyl ferulate, tryptophol, three previously reported bitter-tasting peptides, and two novel ethyl esters of the peptides of 10 amino acid residues were identified. All the identified compounds had a similar taste character to that of the TDA fractions analyzed. Ethyl ferulate and the ethyl ester of the peptides showed a moderately bitter taste. The concentration of the identified compounds in seven jyunmai-type sake samples was determined. This concentration was decreased dose dependently by a charcoal treatment which is commonly applied in the final step of sake manufacture, notably with the compounds of high hydrophobicity.
    Bioscience Biotechnology and Biochemistry 07/2012; 76(7):1291-5. DOI:10.1271/bbb.120046 · 1.21 Impact Factor
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    ABSTRACT: Some oligopeptides and amino acids have a strong influence on the sensory qualities of sake, but the formation process of such compounds in sake mash has not been well elucidated. In this study, we investigated the formation process of bitter-tasting peptides derived from rice proteins in sake mash, because knowledge about their formation may contribute to the quality control of sake. We analyzed rice protein hydrolysates in sake mash, as well as in the enzymatic digest of steamed rice grains digested by either sake-koji or by crude enzyme extracted from sake-koji. SDS-PAGE showed that a smaller amount of polypeptides (>M.W. 10,000) accumulated in the supernatant of sake mash than in either enzymatic digest. The concentration of peptides in the supernatant of sake mash increased gradually from the early stages of fermentation. Five bitter-tasting peptides (No. 9, <QLFNPS; No. 13, <QLFNPSTNP; No. 17, <QLFNPSTNPWH; No. 18, <QLFNPSTNPWHSP; No. 20, <QLFGPNVNPWHNP), which were previously found in sake mash, were not found in significant amounts in sake-koji. On the other hand, these peptides accumulated at the early stages of both sake mash fermentation and the enzymatic digests, although the levels in sake mash were higher than those in the digests. The present study demonstrated that the 5 bitter-tasting peptides formed in high concentrations when steamed rice grains were digested under conditions of sake mash fermentation with yeast.
    Journal of Bioscience and Bioengineering 06/2011; 112(3):238-46. DOI:10.1016/j.jbiosc.2011.05.006 · 1.79 Impact Factor
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    ABSTRACT: The influence of nitrogen and sulfur compounds in rice grains on changes in flavor in stored sake was investigated using Japanese rice cultivars for sake making. Nitrogen content exhibited a significant positive correlation with sulfur content. Based on the molar ratio of nitrogen to sulfur in the rice grain. the sulfur compounds appeared to be derived from protein-associated sulfur-containing amino acids, as reported previously. The higher the protein content of the rice, the greater the amount of nitrogen and sulfur compounds found in both the digest of steamed rice grains and in the sake. Physicochemical changes were investigated in the stored sake to confirm the influence of total sulfur content. Polysulfides in the stored sake appeared to be higher when made from rice grains of high total sulfur content. Staling of stored sake was affected by levels of protein-associated sulfur-containing amino acids in the rice.
    Cereal Chemistry 09/2009; 86(5):0909041222-541. DOI:10.1094/CCHEM-86-5-0534 · 1.06 Impact Factor
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    ABSTRACT: High-molecular-weight peptides (approximately 10-30 kDa) generated in a digest of steamed rice grains by sake koji enzymes were characterized. Among 13 major spots resolved by 2-D gel electrophoresis, 12 contained peptides having N-termini of rice glutelin as determined by mass fingerprinting analysis and/or MS/MS. The source of these peptides was presumed to be the acidic subunit of rice glutelin. An addition of up to 25% glucose in the digestion of an isolated rice protein body induced the accumulation of these peptides. The level of accumulation of these peptides in the digest of 70% polished rice samples correlated well with the crude protein content of the rice grains. The degree of accumulation of these peptides in Yamadanishiki and low-polish-rate rice was low, whereas that observed in 90% polished rice samples was extremely low.
    Journal of Bioscience and Bioengineering 11/2007; 104(4):251-6. DOI:10.1263/jbb.104.251 · 1.79 Impact Factor
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    ABSTRACT: Five bitter-tasting peptides were isolated from charcoal-untreated sake, following a Sepabeads resin separation, an initial reverse-phase chromatography (RP-HPLC), a gel permeation-chromatography, and a second RP-HPLC. The isolated peptides consisted of six to thirteen amino acid residues. The N-termini were uniformly pyroglutamate residues. Based on the rice protein database, the peptides were derived from two different N-termini of the rice glutelin acidic subunit. One of them was reported as a prolyl endopeptidase inhibitor. The thirteen amino acid peptides in charcoal-untreated ginjyo-type sakes were lower than that in charcoal-untreated jyunmai-type sakes. The thirteen amino acid peptides were not detected in the commercial ordinary-type sake analyzed. The concentration of analyzed peptides of nine to thirteen amino acid residues in charcoal-untreated sake exceeded their preliminary estimated sensory threshold values, suggesting that they contribute to the sensory quality of charcoal-untreated sake.
    Food Science and Technology Research 08/2007; 13(3):270-274. DOI:10.3136/fstr.13.270 · 0.36 Impact Factor
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    ABSTRACT: The digestion of proteins in steamed rice grains by sake koji enzymes under simulated sake mash conditions was analyzed by comparing the hydrolysis of steamed rice grains and heat-treated protein bodies (PBs) isolated from seven rice samples including four endosperm-storage protein mutants. The disappearance of peptides in the digest of isolated PBs was faster than that of steamed rice grains; however, more insoluble proteins formed in the case of isolated PBs. Not all of the hydrolyzed PB proteins were immediately solubilized in the digestion tests. High-molecular-weight peptides were more abundant in the solubilized digest of steamed rice grains than in that of isolated PBs. Variance in Ile, Ser, Glu, and Gly levels in the digest of steamed rice grains was relatively high among the seven samples, but was not found to be high in digests of isolated PBs. These results indicate that factors that may be derived from the steamed rice grains profoundly affect the digestion of proteins in steamed rice grains by sake koji enzymes.
    Journal of Bioscience and Bioengineering 11/2006; 102(4):340-5. DOI:10.1263/jbb.102.340 · 1.79 Impact Factor
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    ABSTRACT: Cereal Chem. 83(2):143-151 Structural and physicochemical characteristics of endosperm starch from milled rice grains of seven Japanese cultivars used in sake production were examined. Amylose content was 15.2-20.2%, number- average degree of polymerization (DPn) of amylose was 900-1,400, and the ratio of short-to-long chain amylopectin was 2.7-3.5, respectively. The degree of retrogradation of purified starch stored for seven days at 4°C after gelatinization was 20-31%. The degree of retrogradation correlated negatively with the ratio of short-to-long chain amylopectin. The effect of holding time after steaming on enzyme digestibility and starch retrogradation of steamed rice grains was investigated. The longer the holding time after steaming, the greater the extent of retrogradation, and the less the degree of enzymatic digestibility. The decreased rate of enzyme digestibility correlated with amylopectin chain length distri- bution. Samples with short-chain amylopectin exhibited a slow decrease in enzyme digestibility. It was determined that the structure and retro- gradation properties of endosperm starch in Japanese rice cultivars affect the decreasing rate of enzyme digestibility of the steamed, milled rice
    Cereal Chemistry 03/2006; 83(2):143-151. DOI:10.1094/CC-83-0143 · 1.06 Impact Factor
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    Plant Production Science 01/2006; 9(1):78-82. DOI:10.1626/pps.9.78 · 0.92 Impact Factor
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    ABSTRACT: ABSTRACT,Cereal Chem. 82(4):361–368 Using rice samples derived from normal rice cultivars and endosperm
    Cereal Chemistry 07/2005; 82(4):361-368. DOI:10.1094/CC-82-0361 · 1.06 Impact Factor
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    Plant Production Science 01/2005; 8(5):586-591. DOI:10.1626/pps.8.586 · 0.92 Impact Factor
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    ABSTRACT: Two different alpha-L-arabinofuranosidases from Aspergillus kawachii were purified and characterized. The two enzymes acted synergically with xylanase in the degradation of arabinoxylan and resulted in an increase in the amount of ferulic acid release by feruloyl esterase. Both enzymes were acidophilic and acid stable enzymes which had an optimum pH of 4.0 and were stable at pH 3.0-7.0. The general properties of the enzymes including pH optima and pH stability were similar to those of Aspergillus awamori. These results suggest that the alpha-L-arabinofuranosidases contribute to an increase in cereal utilization and formation of aroma in shochu brewing. Two different genes encoding alpha-L-arabinofuranosidases from A. kawachii, designated as AkabfA and AkabjB, and those from A. awamori, designated as AwabfA and AwabjB, were also cloned and characterized. The difference between the sequences of AkabfA and AwabfA was only one nucleotide, resulting in an amino acid difference in the sequence, and the enzymes were assigned to family 51 of glycoside hydrolases. On the other hand, the differences between the sequences of AkabjB and AwabjB and between their encoding proteins were two nucleotides and one amino acid residue, respectively, and the enzymes were assigned to family 54 of glycoside hydrolases. On comparison of the abfA and abjB genes among A. kawachii, A. awamori, and A. niger, the relationship between the two genes for A. kawachii and A. awamori was much closer than those between A. niger and the others. Northern analyses showed that transcription of AkabfB was greater than that of AkabfA in the presence of L-arabitol and L-arabinose, and that transcriptions of both genes were not induced in the presence of sucrose and glucose.
    Journal of Bioscience and Bioengineering 02/2003; 96(3):232-41. DOI:10.1016/S1389-1723(03)80187-1 · 1.79 Impact Factor
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    ABSTRACT: Sake, a traditional alcoholic beverage in Japan, is brewed with sake yeasts, which are classified as Saccharomyces cerevisiae. Almost all sake yeasts form a thick foam layer on sake mash during the fermentation process because of their cell surface hydrophobicity, which increases the cells' affinity for bubbles. To reduce the amount of foam, nonfoaming mutants were bred from foaming sake yeasts. Nonfoaming mutants have hydrophilic cell surfaces and no affinity for bubbles. We have cloned a gene from a foam-forming sake yeast that confers foaming ability to a nonfoaming mutant. This gene was named AWA1 and structures of the gene and its product were analyzed. The N- and C-terminal regions of Awa1p have the characteristic sequences of a glycosylphosphatidylinositol anchor protein. The entire protein is rich in serine and threonine residues and has a lot of repetitive sequences. These results suggest that Awa1p is localized in the cell wall. This was confirmed by immunofluorescence microscopy and Western blotting analysis using hemagglutinin-tagged Awa1p. Moreover, an awa1 disruptant of sake yeast was hydrophilic and showed a nonfoaming phenotype in sake mash. We conclude that Awa1p is a cell wall protein and is required for the foam-forming phenotype and the cell surface hydrophobicity of sake yeast.
    Applied and Environmental Microbiology 05/2002; 68(4):2018-25. DOI:10.1128/AEM.68.4.2018-2025.2002 · 3.95 Impact Factor
  • HITOSHI SHIMOI, MASAKI OKUDA, KIYOSHI ITO
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    ABSTRACT: Kyokai no. 7 is the most widely used yeast in sake brewing. This yeast is a pantothenic acid auxotroph at 35°C, and this phenotype has been used to distinguish Kyokai no. 7 from other sake yeasts. We cloned a DNA fragment complementing the pantothenic acid auxotrophy from a genomic library of a Saccharomyces cerevisiae laboratory strain. DNA sequence analysis revealed that the DNA fragment encodes ECM31, the deletion of which had previously been identified as a calcofluor white-sensitive mutation. The ECM31 product is similar to the Escherichia coli ketopantoate hydroxymethyltransferase. Disruption of ECM31 in a laboratory S. cerevisiae strain resulted in pantothenic acid auxotrophy, indicating that ECM31 is also involved in pantothenic acid synthesis in yeast. A hybrid of a Kyokai no. 7 haploid and the ecm31 disruptant required pantothenic acid at 35°C for its growth, suggesting that Kyokai no. 7 possesses a temperature-sensitive allele of ECM31. Thus, the ECM31 gene can be used as a selective marker in the transformation of Kyokai no. 7.
    Journal of Bioscience and Bioengineering 01/2000; 90(6):643-647. DOI:10.1263/jbb.90.643 · 1.79 Impact Factor