Masaki Okuda

National Research Institute of Brewing, Edo, Tōkyō, Japan

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Publications (29)27.9 Total impact

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    ABSTRACT: The relationship between the protein composition of rice and nitrogen compounds (amino acids and oligo-peptides) in the produced sake were investigated using endosperm protein mutant rice (LGC-1, LGC-Jun, Kx433, QA28), sake rice (Yamadanishiki) and cooking rice (Nipponbare, Nihonmasari, Koshihikari). The total nitrogen concentration, amino acid concentration and most peptide peak areas determined by RP-HPLC and gel filtration chromatography of the produced sake were lower when sake was made from a low glutelin content rice mutant compared with other rice varieties. The concentration of nitrogen compounds in the sake positively correlated with the glutelin content of the highly milled rice grains used for sake production. Sake produced using a low glutelin content rice mutant is generally evaluated as having a light taste. Our findings suggest that nitrogen compounds (oligo-peptides and amino acids) derived from rice glutelin significantly contribute to the taste of sake.
    No preview · Article · Jan 2016 · Journal of Bioscience and Bioengineering
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    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.
    No preview · Article · Jan 2014 · Cereal Chemistry
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    ABSTRACT: Ferulic acid (FA) and ethyl ferulate (EF) in sake and mirin samples were quantified. Concentrations of FA and EF in the sake and mirin samples showed high correlations (r = 0.91 and 0.89, respectively). The highest level of EF in the sake samples was ca. 14-fold that of the mirin samples. Thresholds of FA and EF in a sake sample were estimated using a pipette method as 0.075 mg/L and 0.39 mg/L, respectively, by eight assessorsin their twenties. The FA threshold was far lower than the highest level of FA in the sake samples, which suggested that FA might affect the sensory quality of sake. FA addedto the sake sample showed unpleasant bitter, astringent, "egumi", or irritating taste characteristics. Sensory and instrumental analyses suggested that EF has the ability to mitigate the taste of FA in sake.
    No preview · Article · Jul 2013 · Food Science and Technology Research
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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.
    No preview · Article · Apr 2013 · Journal of Bioscience and Bioengineering
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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.
    No preview · Article · Feb 2013 · American Journal of Enology and Viticulture
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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.
    No preview · Article · Jul 2012 · Journal of Bioscience and Bioengineering
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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.
    No preview · Article · Jul 2012 · Bioscience Biotechnology and Biochemistry
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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.
    No preview · Article · Jun 2011 · Journal of Bioscience and Bioengineering
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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.
    No preview · Article · Sep 2009 · Cereal Chemistry
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    ABSTRACT: Using the sake samples presented at a sake contest in 2006, we investigated the relationships between concentrations of nitrogen⁄sulfur compounds before the storage of sake and concentrations of polysulfides(DMTS, DMDS)which are the main aroma compounds responsible for “hineka” in sake after the storage of sake, for a month at 50°C. The concentrations of total nitrogen in the sakes exhibited significantly positive correlations with the concentrations of sulfur compounds in the sakes. This result appeared to show that most of the sulfur compounds are derived from rice proteins. The ratio of sulfur of the amino acid formed against total sulfur averaged. 27.6%(min.17∼max.45%)in the sake samples. After storing the sake samples, the concentrations of DMDS were below the detection threshold in all samples, and those of DMTS were above the detection threshold in half of the samples. The concentrations of polysulfides in the sakes after storing showed significant positive correlations with concentrations of sulfur compounds in the sakes before storing. Moreover, a partial correlation analysis showed that the concentration of amino acid containing sulfur had a significant positive correlation with that of polysulfide. These results suggest that sake containing high concentrations of sulfur compounds can produce a high concentration of polysulfide after storage for long periods.
    Preview · Article · Jan 2009
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    Katsumi HASHIZUME · Masaki OKUDA
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    ABSTRACT: Correlation coefficients between the national mean data of sake cake ratios and mean data of monthly atmospheric temperatures of 21 meteorological observation points in Japan showed positive peaks in September, but did not show clear tendencies in winter. The results obtained suggest that atmospheric temperature conditions during the grain-filling period of material rice strongly affect the digestibility of steamed rice grains in sake mash. On the other hand, the effect of atmospheric temperature conditions during winter was not clearly observed.
    Preview · Article · Jan 2008
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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.
    No preview · Article · Nov 2007 · Journal of Bioscience and Bioengineering
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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.
    No preview · Article · Aug 2007 · Food Science and Technology Research
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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.
    No preview · Article · Nov 2006 · Journal of Bioscience and Bioengineering
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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
    No preview · Article · Mar 2006 · Cereal Chemistry
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    ABSTRACT: The behavior of nitrogen was analyzed in conditions of small scale sake brewing and subsequent pressing under actual manufacturing like conditions. About 55% of the nitrogen in the material rice was liquefied in the sake mash, 30-33% was transferred to the sake obtained, and 22-25% was transferred to the yeast. About 44-47% of the nitrogen in the sake was free amino acid, and almost all the residue of the nitrogen was believed to be peptides. We could not cassify about 17-20% of nitrogen in the sake cake and lee.
    Preview · Article · Jan 2006
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    Preview · Article · Jan 2006 · Plant Production Science
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    ABSTRACT: By successive crossing using Hattan-type varieties originating from "Hattanso" as a parent, "Hattan-type varieties" of rice suitable for brewing the original Hiroshima sake have been bred. In this study, the difference in the properties of starch and protein among the Hattan-type varieties was examined. Six Hattan-type varieties, Hattanso, Hattan No.10, Hattan No.35, Hattan No.40, Hattan-nishiki No.1 and Hattan-nishiki No.2, were used. As the properties of starch, amylose content, pasting properties and gelatinization properties were examined. The pasting and gelatinization properties were examined using a rapid viscoanalyzer (RVA) and a differential scanning calorimetry (DSC), respectively. As the properties of protein, the compositional ratio of two types of protein bodies (PB-II/PB-I) was analyzed. However, no significant differences in the above properties were observed among these Hattan-type varieties. The above properties of starch and protein in Hattanso seem to be retained in all of these varieties. In these varieties, breeding might not have been aimed at improvement of the properties of starch and protein.
    Preview · Article · Dec 2005 · Plant Production Science
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    ABSTRACT: Using rice samples derived from normal rice cultivars and endosperm starch mutant, we investigated key factors contributing to the enzyme digestibility of steamed rice grains. The chemical composition of polished rice grains, structural features of endosperm starch, and enzyme digestibility of steamed rice grains were examined. The protein content of polished rice grains was 4.6-9.1%, amylose content was 4-27%, the DPn of purified amylose was 900-1,600, the amylopectin short/long chain ratio was 1.2-5.9, and the enzyme digestibilities of steamed polished rice grains were 0.9-12.6 °Brix. Amylose content and RVA parameters (viscosity, breakdown, and setback) correlated significantly with enzyme digestibility of steamed rice grains. Multiple regression formulas were constructed to predict digestibility of steamed rice grain as a function of the molecular characteristics of the starch. When both amylose content and the short/long chain amylopectin ratio were used as predictor variables, they accounted for >80% of the observed variance in digestibility of steamed rice grains. Multiple regression revealed that the more digestible rice samples had starch with a lower amylose content and more short-chain amylopectin. Reassociation of amylose-lipid complex and recrystallization of amylopectin in the stored steamed rice grains was monitored by differential scanning calorimetry (DSC), and the observed retrogradation properties were related to the structural characteristics of starch and to the enzyme digestibility of steamed rice grains.
    No preview · Article · Jul 2005 · Cereal Chemistry
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    ABSTRACT: The broken rice ratio at milling of long-term stored rice grains was closely related with the moisture content of the brown rice grains. Rice grain samples of low moisture content (11-13%) showed a low broken rice ratio in the milling process, while the broken rice ratio of the samples of high moisture content (over 15%) was very high. Drying treatment of the long-term stored rice grains was effective in preventing the breaking of rice grains in milling, and the availability of the treatment was confirmed using a 60 kg scale mill. Hardness of the long-term stored rice grains varied along with the moisture content of the rice grains. The relation between the hardness and the moisture content was not the same in the two examined samples, a finding which might affect the frequency of the breaking of different rice samples at the milling process. Drying treatment slightly raised the hexanal content of rice grains, and also raised the water absorption ratio of the polished rice grains.
    Preview · Article · Jan 2005