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About Sake
Shubo, also known as moto, is second in importance only to the koji. Yeast fungi play a part in the alcoholic fermentation that produces alcohol from glucose. Shubo is a liquid containing such yeast fungi; the koji is dissolved in this liquid to create a "starter mash" that will promote the growth of yeast. Lactic acid adds a vital assist by suppressing contamination with miscellaneous bacteria. This enables sake brewers to produce pure cultures of high-quality yeast in the starter mash. In the old days, sake brewers took advantage of the fact that lactic acid produced by naturally occurring lactobacilli held down the propagation of other microorganisms. These lactobacilli were eventually killed off when the lactic acid they produced caused the pH to become lower. This mechanism ensured the selective survival of only superior yeast fungi. Today, sake brewers help this process along by adding lactic acid to the shubo. After the mixture has been cultured for 8 days, it is ready to use in moromi.
The moromi is allowed to ferment for about 15 or 16 days in a tank kept at a low temperature of 10 to 16 degrees centigrade (50 to 60 degrees Fahrenheit). Steamed rice and water are added to the moromi in three installments lest the action of the yeast fungi be extenuated by addition of large quantities of rice and water all at once; this is called "three-stage preparation." As the fermentation progresses, the distinctive and robust aroma produced by the yeast rises from the tank of moromi.
This sterilization process is identical to the low-temperature pasteurization process for wine discovered by French microbiologist Louis Pasteur (1822-96), but Japanese sake brewers began pasteurizing genshu at low temperatures in this way about three centuries before Pasteur's discovery, starting around the year 1560. After pasteurization, the genshu is aged in storage tanks (chozou tanku) for several months. Only then it is blended, bottled, and shipped to market as the final product. |
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Seikiku is the process of producing koji, or malted rice. Koji
is made by sprinkling spores of koji-kin, a beneficial type of
mold, on steamed rice and then culturing the spores. Alcoholic fermentation
cannot take place without glucose, the raw material of alcohol. In sake-making,
glucose is formed by breaking down the starch in the rice, and enzymes
like amylase play a key role here. Heightening the action of these enzymes
is crucial to the success of the process, and malted rice production is
considered the most important as well as the most difficult step in the
making of sake. As the old saying goes among sake brewers, "First and
foremost, the koji; second, the moto; third, the sake-brewing itself."
Moromi is made by
mixing koji, steamed rice,
and water together with the shubo. In this "main mash," two reactions
take place simultaneously: glucose production occurring when the koji breaks down the
steamed rice (saccharification), and production of alcohol from that glucose
by the yeast (alcoholic fermentation). Together, these two reactions are
known as "parallel compound fermentation." This process is a unique characteristic
of the production of sake.
The liquid that remains after the moromi
has been pressed and filtered is seishu (refined sake), also known as genshu. Genshu has an alcohol
content of 18% or higher, so it generally will not support the growth
of bacteria. However, should a type of alcohol-resistant lactobacilli
known as karaku-kin begin to propagate, such untreated sake will go bad.
To prevent this from happening, the genshu is sterilized by means of low-temperature pasteurization
at about 65 degrees centigrade. Sake brewers call this process hi-ire (heating).