Happo Nihon-shu (発泡日本酒)

Happo Nihon-shu (sparkling Japanese sake) is sparkling, that is, carbon-dioxide-containing Japanese sake which has attracted attention in recent years. This is also called happo sei-shu (sparkling clear Japanese sake). When the words 'kassei-shu' (active sake) are written on the label, this often means to be sparkling. Most types of this sake are cloudy due to their dregs and, therefore, they are also called happo nigori-zake (sparkling cloudy sake) or kassei nigori-zake (active cloudy sake).

History
This sake has been produced in some of the sake producers since the World War II started. Though this sake has not attracted attention for long time, this sake suddenly started to be highlighted in the market as a part of the current style of Japanese sake after the Heisei period started.

Production method
The production methods of this sake includes an in-bottle secondary fermentation method which is similar to that of champagne, and a carbon-dioxide-injection method. Some types of sei-shu (clear Japanese sake) are slightly sparkling immediately after they are collected by pressing due to their dissolved carbon dioxide.

In-bottle secondary fermentation method
Moromi of Japanese sake in which alcoholic fermentation has not yet been stopped, is bottled without being heated and in the state where the yeast in it is still alive and, thereby, the fermentation is further fermented in the bottle and carbon dioxide is confined within the bottle. This method is often used for junmai-shu (genuine-rice Japanese sake).

This production method is a production method that is similar to that of Champagne as opposed to wine.

Carbon-dioxide-injection
This is a method of dissolving carbon dioxide into sake of low alcohol content to produce happo Nihon-shu. This method is suitable for sake which is the original thick sake of Nihon-shu Junmai-shu, to which no water is added, and which is filtered with carbon.

About 10 days after carbon dioxide is added, Nihon-shu moromi is pressed to take out sake and this sake is added with Nihon-shu yeast and is fermented, then, the carbon dioxide produced is dissolved as it is at a low temperature, and the sake is shipped.

Feature
Similarly to sparkling wine which is also sparkling, it is strictly prohibited to swing or shake the bottle before it is opened and, in order to open the bottle, care must be taken to loosen the cap and, when foams are generated, the state must be observed and the cap must be slowly opened.