Masaki Okuda

National Research Institute of Brewing, Edo, Tōkyō, Japan

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Publications (13)11.69 Total impact

  • [Show abstract] [Hide abstract]
    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; · 1.74 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; · 1.74 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. · 1.27 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. · 1.74 Impact Factor
  • Cereal Chemistry - CEREAL CHEM. 01/2009; 86(5):0909041222-541.
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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. · 1.74 Impact Factor
  • Food Science and Technology Research - FOOD SCI TECHNOL RES. 01/2007; 13(3):270-274.
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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. · 1.74 Impact Factor
  • Source
    Plant Production Science - PLANT PROD SCI. 01/2006; 9(1):78-82.
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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 - CEREAL CHEM. 01/2006; 83(2):143-151.
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    Plant Production Science - PLANT PROD SCI. 01/2005; 8(5):586-591.
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    ABSTRACT: ABSTRACT,Cereal Chem. 82(4):361–368 Using rice samples derived from normal rice cultivars and endosperm
    Cereal Chemistry - CEREAL CHEM. 01/2005; 82(4):361-368.
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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. · 1.74 Impact Factor

Publication Stats

34 Citations
11.69 Total Impact Points

Institutions

  • 2012–2013
    • National Research Institute of Brewing
      Edo, Tōkyō, Japan
    • Akita Prefectural University
      Akita-shi, Akita, Japan