[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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After fermenting several types of sake cake using the natto bacillus (Bacillus subtilis natto), it wasfound that a large amount of nattokinase or vitamin K₂ (menaquinone-7) was produced both throughstationary culture and liquid culture.
Of ten types of sake cakes, or cakes made in the process of distilling, the sweet potato spiritproduced the largest amount of nattokinase. The amount of nattokinase produced from 100 g of drycultured substance was equivalent to over 168, 000 IU of urokinase. It was also found that menaquinone-7, which was not produced by using the HPLC method, was fermented up to a concentration of over31.73 mg.
Considering the fact that nattokinase and vitamin K₂ are known to be the functional ingredientsproduced by the natto bacillus and have shown positive effects for certain conditions now keenlyfollowed by the public (senile dementia and osteoporosis), the fermentation technology applied this timemight prove to be a promising method for the effective use of sake cake made from distilled spirits, whose non-utilization and disposal has come to be deplored.

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High gravity brewing has come to be widely used for increased brewery efficiency. However, it is not easy to maintain good yeast performance during fermentation because of the stress on yeastcaused by high sugar and/or ethanol concentrations. Therefore, sugar attenuation tends to be insufficientand the finished beer contains high concentrations of acetic acid and esters.
We previously reported on the development of a new fermentation method by which severaldifficulties in high gravity brewing could be overcome. In this method, α-glucosidase added at thebeginning of fermentation enables the conversion of wort sugars by glycosyl-transfer and hydrolyticreactions to proceed in parallel with ethanol formation by yeast. By using α-glucosidase, we succeededin high gravity brewing with a top fermentation brewer's yeast at a constant fermentation temperatureof 15°. However, bottom fermenting brewer's yeast is more widely used for commercial brewing aroundthe world. In this paper we report results of using the method with bottom fermenting brewer's yeast. We confirmed that the method could be successfully applied to high gravity wort fermentation withbottom fermenting yeast at low temperature. When α-glucosidase was added to 20% Plato wort at aconcentration of 800mg/l, the wort was successfully fermented at 10° with a bottom fermenting brewer's yeast, W 34/70. The real degree of fermentation was 77%, which was 16% higher than that ofthe control fermentation, and the concentration of acetic acid was 200mg/l, which was 85mg/l lowerthan that of the control. The addition of α-glucosidase was also effective for increasing the degree offermentation of dextrinous wort. When α-glucosidase was added at the concentration of 400mg/l to 20% Plato wort containing 6.2% dextrin, the content of dextrin decreased to 3.7% by the end of fermentationwith a top fermenting brewer's yeast, NCYC 1245; the real degree of fermentation was 75%, whichwas 19% higher than that of the control. It is suggested that the use of α-glucosidase is applicable forbrewing good beers from wort that have a low proportion of fermentable sugars, meaning that malt withlower diastatic power could be utilized. The use of enzymes in fermentation would open several newpossibilities to add to existing enzyme methods, such as the use of acetolactate decarboxylase to shortenthe conditioning period or glucoamylase for dry beer brewing.

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From a total of 314 yeast strains that have beenisolated from sake-mash made at sake breweries in Fukuoka Prefecture, 24-2 was isolated as the mostmalic acid-producing yeast strains and produced 1.7 times more malic acid than K-9, using a fermentationtest in YM-10 broth and koji-extract. K-9 and 24-2 were tested for CO₂ evolution, alcoholproductivity, acidity, amino acidity, organic acidproductivityinvolving malic acid, and flavor-productivityusing a small scale sake fermentation test. Strain 24-2 produced 2.2 times more malic acidthan K-9 and is suitable for sake brewing. Moreover, 24-2 also produced 2.5 times malic acid than K-9 using a small scale low alcohol sake fermentationtest. Low alcohol sake brewed with 24-2 results in agood taste balanced between sweetness and acidity.

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We determined the amakara (Dryness) categoriesof sake for type designation. Multiple regressionanalysis was applied to sensory evaluation scores bya trained panel and chemical data (R²=0.797).
We defined the following discriminant model ofamakara by simplification of the regression equation.
AV=G-A
AV: Amakara Value, G: Glucose (g/dl)
A: Total acidity (ml)
Karakuchi (DRY): AV<=0.2, Yaya karakuchi (Medium Dry): 0.3<=AV<=1.0, Yaya amakuchi (Medium Sweet): 1.1<=AV<=1.8, Amakuchi (Sweet): AV>=1.9
To verify this model, the calculated amakara values were compared with sensory intensities of amakara by two types of panels: one a panel withmuch experience of drinking sake (NRIB trainee) and the other a panel with little experience (Universitystudents). Amakara values correlated well tosensory intensities of amakara by both panels (R²=0.712, R²=0.757).

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