Yumai-zukuri is the modern method for brewing sake (rice wine) wherein rice is reduced to a gruel-like consistency to enable saccharification at a high temperature. The method was developed by the major sake brewing company Gekkeikan. It characteristically treats sake as a modern industrial product suited to today's needs rather than a traditional craft, as it is for Baisho-zukuri (the brewing method wherein rice is heated in hot air). This is the point where the opinions are still divided.
First the rice is polished, then washed and soaked in sake so that it absorbs it, and is liquidized with the blender-like machine with water mixed with sake. The heat-stable enzyme, which breaks down the protein, is added to the liquid, which is then cooked with steam of about 100 degrees Celsius. In about 10 minutes, the rice protein melts and becomes oligosaccharide and is liquidized. The chilled liquid is preserved with sake rice malt and sake yeast in tanks and is fermented. In this way, sake can be produced at a lower cost without wasting raw materials and labor cost in comparison to the traditional brewing method.
Advantages and approving opinions
Rice can be used without being wasted.
It is cost efficient in terms of time and labor.
The sake ferment (moromi) is controlled more easily.
It can produce sake with crispy and dry taste in comparison to the normal steaming method. (The sake meter value [a numerical rating of a sake's sweetness or dryness] of Josen [high quality sake] was +6, and Ai label [extra] was +5, which were made with the yusen-zukuri method and are no longer on the market.
The sake meter value of the average Josen, Dry is +5 and Ko no Tsuki, Dry [extra] is +3, which are both available on the market.)
The producer can control sake in a modern way and can maintain the stock as an industrial product.
During the difficult time when sake was consumed less and sold less while the labor and other managerial cost was soaring, the yumai-zukuri method became a new hope for producing and selling sake easily.
Although the consumers who are experts of sake often complain that sake produced with the yumai-zukuri method is sold for almost double of the real price, in fact the retail price is determined according to the current market price which includes the marketing cost and others, and as such, the consumers should respect the price which is determined by their choice according to the current market price.
The sake lees (kasu), which are produced during the production process, cannot be used as edible "sake kasu" and they are disposed as industrial waste.
However, some producers are now researching about the use of sake lees which are produced during the process of liquefaction.
In terms of the quality as sake, it lacks the authenticity and body.
Negative opinions based on the misunderstanding of the yumai-zukuri method
The necessary protein is drained during the process in which the rice is melted and squeezed; therefore, there is no point in adding the sake rice malt to it afterwards.
There is not a process of 'squeezing' after melting the rice. The liquid of melted rice is used entirely, to which malt and yeast are added to encourage fermentation.
In some ways, sake rice malt is added solely for the purpose of being categorized as "refined sake" according to the Liquor Tax Act.
During the process of melting the rice, starch is broken down to oligosaccharide. At this stage, the percentage of glucose, which is consumed by yeast, is almost none, and the fermentation does not occur by adding yeast to the melted rice. In order for the fermentation to occur, the sake rice malt needs to be added to the melted rice (in which the amount of malt must be more than 3% of the amount of rice), so that it is broken down to glucose which can be consumed by yeast.
Therefore, the sake rice malt is not added only for the purpose of being categorized as 'refined sake.'
Although one may insist that the multiple parallel fermentation is carried out as the process includes the adding of the sake rice malt, it is in fact brew as in the case of beer.
It is considered the multiple parallel fermentation, and not the single fermentation, because the dissolving process, in which the melted rice is turned to glucose, and the fermentation process, in which glucose is turned to ethanol, are in progress at the same time.