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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. more

Using rice grains contaminated with radioactive cesium (134Cs and 137Cs) 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 40K) 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. more

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 133Cs, 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 133Cs 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 133Cs 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 133Cs from rice to sake was examined. Approximately 30–40% of 133Cs in the 70% polished rice was removed during the washing and the steeping of the rice grains, and approximately 40% of the 133Cs 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. more

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. more

Background and objectives Protein composition analysis of 81 rice samples was performed on three cultivars harvested different regions in Japan, and the effects of the protein composition on the ... nitrogen composition in sake. Findings Crude protein content showed a significant positive correlation with glutelin content. Yamadanishiki cultivars showed lower crude protein and glutelin contents compared with Gohyakumangoku cultivars harvested from the same field. Total nitrogen content in the enzyme digest of steamed rice grains showed a significant positive correlation with the crude protein and glutelin contents. Ten polished (70%) white rice samples were investigated in a small‐scale sake brewing test. Total nitrogen compounds, bitter‐tasting peptides, and free amino acids in the brewed sake positively correlated with the glutelin content of the rice samples. There were no clear correlations between α‐amylase and acid proteinase activities with the nitrogen compounds in the sake. Conclusions The results indicated that the glutelin content in the cultivar rice affects sake quality through taste‐active and other nitrogen‐containing compounds produced from rice glutelin in the sake brewing process. Significance and novelty We revealed that the glutelin content in the milled rice grains is important to brew high quality of sake clearly. The present results would be useful for cultivation or breeding of sake rice. more

Thai non-broken rice has been mainly used for the production of awamori after 2010. It is more difficult to absorb water ideally than for Thai broken rice, which has been mainly used for a long time. ... This difficulty in absorption for Thai non-broken rice has recently demanded on immediate solution. In the present study, to obtain the basic knowledge for improving the absorption of Thai non-broken rice, we examined the suitability of Thai rice used for awamori production compared with Nipponbare, which is used for sake making. The property of Thai rice starch by RVA analysis was significantly different from that of Nipponbare. The water absorption ratio of rice showed a negative correlation with the moisture of rice grains in both Thai rice and Nipponbare. However, the ratio of water absorption of Thai rice was lower than that of Nipponbare, when the moisture of the rice was same. The speed of water absorption was significantly improved by pulverizing the rice grains when the steeping time was short. Two steamings also significantly improved the ratio of water absorption of steamed rice and enzyme digestibility. From the above results, we recommend that prevention of an increase in the moisture of rice grains is important to deal with Thai rice appropriately. Also, sufficient steeping time, or two steamings are effective to achieve the ideal ratio of water absorption when using Thai rice. more

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. more

酒の四つの原材料（水，米，酵母，米麹）のうち，水と米だけが生産地に関わる物理的条件の要素として用いることができ，その中でも水は最も決定的な要因である．水は場所を移すことができず，その水質は酒の味に反映することから酒テロワールの代表と見なされている（ボーメール日本語訳，2021）．久田ほかは2021年に「日本酒仕込水の水質と地質」と題したポスター発表を行った．これは，全国およそ1400ある酒蔵のうち，仕込み水として使用している水274点（地下水200点，その他74点；ひとつの酒蔵から複数試料の場合あり；各50 mL）を入手した．仕込み水以外の参考水試料（9点）をあわせて分析総数は283点であった．東北日本，西南日本内帯，外帯の分析試料数は，それぞれ130，147，６であり，溶存イオンの成分比をあらわすキーダイアグラムの全ての領域に分散している．特に東北日本ではアルカリ土類炭酸塩型が50%，中間型が37%，内帯ではそれぞれ64%，24%となっていた．このような水質分析結果から，花崗岩がより広く分布する内帯の地域に位置する酒蔵の仕込み水は，Ca-HCO3 型がより卓越するものと推察した．一方，東北日本の水質ではより中間型の水が多く，これは広く分布する第四紀・新第三紀の地層中の地下水流動に起因するものと推定した． 　今回，その後に分析した仕込み水試料13点を加えて（総計277点の仕込み水のみ），クラスター分析（溶存イオン8成分の濃度を利用）を試み，10のカテゴリーを見出した．その結果，2021年の発表における９のカテゴリ－分類よりもいっそう仕込み水の溶存イオンの特徴が明らかとなった．10のカテゴリーは，基本的には溶存成分量の少ないCa-HCO3 型と比較的多いCa-HCO3 型にわけられる．後者のうち，Ca2+とHCO3-が陽イオン・陰イオンで卓越するもの，Cl-が卓越するもの，SO42-とNO3-が比較的卓越するもの，Na+とK+が比較的卓越するものとなる．このように溶存成分量の多いグループはCa-HCO3タイプとNa(K)-Cl タイプで特徴づけられる．これらの地理的分布を見ると，溶存成分量の少ないグループは全国的に広がり（北海道を除く），多いグループは西南日本内帯に偏る傾向がある．花崗岩・斑レイ岩でできた筑波山の麓ではCa-HCO3タイプが確認されており，岩石による影響を強く受けている（藪崎他，2007）．一般に水質は，岩石の種類・滞留時間などに強い影響を受けるといわれており，溶存成分量の少ないCa-HCO3 型を示す地点は，降水後まもなく地表水・地下水流動し滞留時間が比較的短時間であった可能性がある（急峻地形による）．あるいは火山岩地帯の地下水のように，岩石－水反応が十分でなかったことが示唆される（火山岩の特性による）． 　仕込み水の水質が清酒醸造に及ぼす影響を明らかにするため，国内清酒製造場の仕込み水11種と超硬水と純水の合計13種類の水と精米歩合40%，60%，70%の原料米を用いて清酒小仕込み実験を行ない，水質と清酒成分等との関係を解析した（奥田ほか，2022）．すなわち仕込み水と原料米の無機元素含量から，もろみに投入される仕込み水の影響が大きい元素の特定を行った．清酒小仕込み試験の結果，発酵過程や製成酒成分は超硬水とそれ以外では顕著に異なったが，11種類の清酒仕込み水間においてもバラツキがみられた．製成酒の味覚センサー解析では酸味，苦味雑味・旨味コク，渋味刺激・渋味センサー応答において，仕込み水のMg,　Ca,　SO42-濃度に相関がみられた．とくに各仕込み水中で米の消化性を調べたところ，仕込み水のCa,SO42-濃度が高いと消化液のα-アミラーゼ活性が高くなることが認められた．すなわち，α-アミラーゼの無効吸着が仕込み水の無機成分含有量によって左右され，その結果米の溶解性に影響を及ぼすことが示唆された．一方，消化液のアミノ酸濃度は，仕込み水のCa, SO42-濃度が高いと低くなる傾向が見られた．そして各仕込み水での消化特性は，アミノ酸濃度，香気成分，発酵速度など清酒醸造特性にも高い相関を示した．このように奥田ほか（2022）は，仕込み水のSO42-のような無機成分が，α-アミラーゼの蒸米への無効吸着を抑制し，米の溶解性を向上させる一方で，アミノ酸の生成を抑制する可能性を指摘した． 【文献】　ボーメール(Baumert,2021) 寺尾監訳 酒　日本に独特なもの276pp，晃洋書房． 久田ほか（2021）地質学会第128年学術大会T5-P-1. 奥田ほか（2022）日本醸造協会誌　117(8) 580－608. 藪崎ほか（2007）地下水学会誌，49，153－168

In the present study, we investigated the estimation method for the enzyme digestibility of steamed rice grains for sake making using alkali / urea solubility. Visual observation of the alkali / urea ... concentration solubilizing rice grains showed significant correlations with the DSC（= Differential Scanning Calorimeter）gelatinization temperature, the enzyme digestibility of steamed rice grains, and the retrogradation of steamed rice grains. The absorbance of iodine staining after soaking rice grains in urea solutions measured using a spectrophotometer also showed significant correlations with the enzyme digestibility of steamed rice grains and the retrogradation of steamed rice grains. Therefore, the enzyme digestibility of steamed rice grains for sake making can be estimated easily by the alkali / urea concentration solubilizing rice grains and the absorbance of iodine staining after soaking the rice grains in a urea solution. However, the polishing ratio and the moisture content of rice grains influenced the urea concentration solubilizing rice grains, although the existence of a white-core did not. In conclusion, these methods will be useful to estimate the enzyme digestibility of steamed rice grains for sake making, if the estimation standards according to the polishing ratio and moisture content of the rice grains can be determined. more