<In Japanese here>
Each Japanese sake has very various aroma.
For example you can find some sakes which have aroma of fresh acid like yogult.
I understand the origin of such a aroma is lactic acid bacteria added in the process of Kimoto(生酛) making Yeast Starter.
Yeast that is used for alcoholic fermentation has to be protected from other stronger bacteria.
Adding lactic acid bacteria is very effective way to protect yeast against other bacteria which are weak in acidic environment.
As to Making A Yeast Starter please refer to “Brew Process of Sake“.
Although Kimoto(生酛) making Yeast Starter is traditional way which requires much time and effort, some breweries are keeping this way by which they can succeed in obtainning high quality sake.