By far my favourite sparkling sake ever tried and I’ve had a few.
The sparkling AFS from Kidoizumi Shuzo in Chiba prefecture is a complex, intense sake with a perfect interplay of acidity and sweetness.
A standard sake fermentation starter is made with 3 additions of steamed rice, koji-rice and water over 4 days however at Kidoizumi they take an alternative approach and use a one stage fermentation (ichi-dan-jikomi) where all of the rice, koji rice and water go into one tank along with hot water at 55 degrees. They add the in-house cultured yeast number 701 only at the start of the season around October which is always the riskiest time since the airbourne yeast is in a weaker state and then after a few tanks into the season are able to rely on it fermenting naturally.
With an alcohol content of 13.5% and a rice polishing ratio of 65%, the AFS sparkling just like the non sparkling version is made with the local Fusa-no-mai rice variety and is unpasteurized with no charcoal filtering hence the colour. The AFS sparkling is made with a in-bottle secondary fermentation (瓶内二次発酵) where some of the active lees are also bottled. The advantage of this method over the champagne method is that the carbon dioxide lasts longer once the bottle is open.