[More kimoto secrets]
Overwhelmingly high purity
Among various ways to make the starter mash, the traditional kimoto method uses the highest purity of yeast (almost 100%). The liquid lactic acid added in the initial stage of the sokujomoto method does kill all the bacteria, but it is powerless to keep in check the wild yeast that appears after the acid has broken down and become diluted. In contrast, kimoto brewing has a system in place that culls any wild yeast that may appear.
Low yeast death rate
Kimoto contains more lactic acid and amino acids than sokujomoto. When the mash is completed, the alcohol content is low. This means that the yeast death rate during the final karashi (period when the yeast is rested at a low temperature) can be kept low.
Kimoto yeast has astonishing vitality. It ferments well at low temperatures, and also enjoys a low death rate at the end of the process when ordinary yeast is exhausted. Skilled brewers are amazed that it doesn't stop fermenting even when highly-concentrated alcohol is added to make honjozo sake. It is this strength that makes low-temperature long-term fermentation possible. Kimoto yeast is perfect for the manufacture of top-quality sake.
Sake that doesn't deteriorate
Kimoto sake is characterised by very little deterioration in quality over time. It is thought that because the maturation process is slow, the various components have antioxidative properties, making them far less susceptible to deterioration.
In order for sake to have a rich bouquet, it is necessary to have both fragrant components and natural preservatives to maintain that fragrance. If the latter are lacking, the fragrance dissipates quickly and then disappears. Kimoto ginjo sake is particularly rich in such preservatives, allowing it to maintain its wonderful aroma.
A lactic acid bacterium first discovered at Daishichi Sake Brewery
The research of Prof. Kiyoshi Yoshizawa at Tokyo University of Agriculture revealed that of the five lactic acid bacteria in Daishichi's kimoto starter mash, one variety possesses a highly unusual enzyme that had never been described before. It seems that this lactic acid bacterium is what gives Daishichi its unique quality, setting it apart from the kimoto mash produced by other companies.
This bacterium's enzyme is an acidic arginase. Although neutral arginases have been discovered before, this is the first arginase known to function in such a low-temperature, acidic environment as sake.
The enzyme arginase breaks down amino acids that have an unpleasant bitterness, thus improving the balance of the sake's flavour components.
Let's take a closer look.
The enzyme also works to completely eliminate arginine. This means no harmful ethyl carbamate is produced in Daishichi sake.
From the early moromi stages, the acidic arginase breaks down the arginine, producing urea.
The yeast consumes this, leaving behind only trace amounts of urea in the moromi.
No harmful ethyl carbamate is produced.
The absence of arginine effects a change in how the lactic acid bacteria metabolise amino acids. It has been discovered that the lactic acid bacteria produce aromatic compounds such as high-quality esters.
The "Daishichi lactic acid bacterium" performs a host of useful tasks, and is responsible for no drawbacks.