清酒麹造りは, 有用酵素をバランスよく生産させるために, 様々な経験則がノウハウとして蓄積している。一方近年の分子生物学の進歩とともに, 麹造りでの酵素生産を遺伝子レベルで解析する研究が数多くなされている。筆者らは, 清酒麹造りにおいて培養中期から培養温度を高温にすることでプロテアーゼカ価が低い麹ができることに着目し, プロテアーゼ遺伝子の固体培養での発現状況を検討した。その結果このプロテアーゼ生産の温度依存性は, その遺伝子の転写が高温培養によって抑制されることが原因であることを見いだした。麹造りのノウハウに対して, 科学的な証明を付与できた好例である。

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冬は,「お燗酒」が特においしい季節である。しかし, 徳利に日本酒を入れお湯で温めるのは手間がかかる。手っ取り早いのは電子レンジであるが, 上手にお燗をするのは難しかった。その問題の1つはお燗の温度ムラである。筆者は, 電子レンジによりお燗をした場合の徳利内の温度分布から加熱ムラの要因を明らかにし, 加熱ムラの少ない新しい形状の徳利を提案している。
電子レンジにより, 家庭や料飲店でおいしいお燗酒が簡単にできるようになれば, 日本酒離れの若者にも日本酒を勧める上での強力な手段にもなるし, 日本酒ファンにとっては大変うれしいことである。

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グルコン酸は多くの発酵食品中に, 特に蝉蜜中に多く含まれハチミツ酸と名づけている会社もある。その安全性はすでに公の機関で確認済みで, 多くの食品にその塩類が使用されている。ここではグルコン酸とその各種塩類の特徴と機能の食品への利用例を説明してもらった。近年見出されたグルコン酸塩類の小腸での吸収が少なく, 大部分は大腸に達しビフィズス菌や乳酸菌などに利用され, 短鎖脂肪酸の産生など機能性食品としての評価をも紹介して貰った。

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著者は研究機関にて昭和32年から20年間に亘り, 清酒蒸煮用和釜を使用して清酒製造研究に従事して来た。丁度, 三州釜 (大和釜) の生産が連続蒸煮機の醸造業界への導入と共にその使命を終える時期にあたる。三州 (三河) 地方での三州釜の生産に携わってきた製造業者の栄枯盛衰を史実に則り詳しく解説して貰った。

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Effects of a prefermentation cold soak on extraction of color and phenolic compounds during red wine making were examined. Cabernet Sauvignon and Merlot wine made on a small-scale test with a cold soak at 10°C for 2 days resulted in higher A₅₂₀ (red color), A₄₂₀ (yellow color), and A₅₂₀ at pH 0.25 (anthocyanin concentration) than the control wine without the cold soak. There was no significant difference in A₂₈₀ (index of total phenol concentration) with or without the cold soak. To exclude microorganism activities, a non-fermentation test was performed with addition of 10 mg/l of cycloheximide, 500 mg/l of chloramphenicol, and 200 mg/l of potassium pyrosulfite to crushed grapes. A nonfermentation cold soak at 10°C for 2 days without ethanol followed by soaking at 25°C for 6 days with 5 or 10% ethanol showed higher A₅₂₀, A₄₂₀ and A₅₂₀ at pH 0.25 than the control kept at 25°C for 8 days with ethanol and another control with a cold soak after addition of ethanol. There was no significant difference in A₂₈₀ with or without the cold soak, or with or without ethanol during the cold soak. Thus, keeping crushed grapes for 1 or 2 days without ethanol seemed to be effective for good color extraction during fermentation without excessive extraction of phenolic compounds.

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Sake yeast with high productivity of β-phenylethyl alcohol (P 9-5) was isolated from resistantmutants to p-fluoro-phenylalanine. In performing small scale and the industrial scale sake-brewing tests, β-phenylethyl alcohol was more than doubled in the former test and increased to 1.4-1.7 times in the later test compared with the parent strain (K-9, Nippon Jozo Kyokai). On the other hand, the production of ethanol and the acidity were almost same in both strains, P 9-5 and K-9. To elucidate the high productivity of β-phenylethyl alcohol in P 9-5, the time course of β-phenylethyl alcohol productivity and the amount of m-RNA of the related genes in the biosynthetic pathway of the yeast wereinvestigated. It was considered that the increase in β-phenylethyl alcohol was responsible for the biosynthetic pathway and Ehrlich pathway.

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Mutant MA 2504 carrying gap1 and apf1 (shr3) double mutations and mutant MA 2601 carrying gap1 and can1 double mutations were isolated from the homothallic wine yeast Saccharomyces cerevisiae OC-2. MA 2504 was unable to grow on proline, alanine, aspartate, glutamate, phenylalanine, or valine, and MA 2601 was unable to grow on arginine when these amino acids were added to the medium as the sole nitrogen source. This indicates that the uptake of these amino acids was deficient in the mutants. Fermentation of Koshu grape must by both mutants MA 2504 and MA 2601 was completed to dryness, with a slower fermentation rate than that of the wine yeast OC-2. Supplementing the must with diammonium hydrogenphosphate restored the fermentation rate. Wine produced using MA 2504 retained 985.7 mg/l of total amino acid from must initially containing 1184.1mg/l and no diammonium hydrogenphosphate supplement. This represents almost twice the level of 521.1 mg/l in wine produced by the wine yeast OC-2. Wine produced by MA 2601 contained 662.9 mg/l of the total amino acid. Similar results were also observed in wines made from must supplemented with diammonium hydrogenphosphate. These results indicate that the use of wine yeast mutants carrying gap1 and apf1 (shr3) double mutations or gap/ and canl double mutations effectively improves the amino acid content in Koshu wine.

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Sake yeasts having high malate and succinate productivity were obtained from mutants resistant to α-ketoglutarate. One sake yeast, kyokai no. 701 (K-701), was mutagenized with ethyl methanesulfonate and mutants, which were grown on SD agar plate containing 25 mM α-ketoglutarate at 30°C for 3 d, were selected. Forty-five mutants obtained were used for fermentation in a koji extract medium, and almost all produced higher total acidity and succinate than the parental strain. In a small-scale sake brewing test, One (2 OG-R 39) of these mutants produced a 1.7 times higher total acidity, a 3.0 times higher concentration of malate, and a 1.8 times higher concentration of succinate. However, this mutant exhibited neither resistance to cycloheximide nor sensitivity to dimethyl succinate.

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The functional properties of Kome Shochu Kasu (KSK) fermented by Lactobacillus brevis IFO-12005 and enriched with γ-Aminobutyric acid were investigated.
Fermented and concentrated (x 10) KSK containing heat treated lactic acid bacterial cells [Lac (+)] and not containing lactic acid bacterial cells [Lac (-)] was fed to spontaneously hypertensive rats (SHR) for ten weeks. The blood pressure in the fermented KSK groups, for both Lac (+) and Lac (-), was significantly lower than that in the control group, indicating that GABA suppressed an increase in blood pressure of SHR.

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