Excite News has an article on bodaimoto (菩提酛, Bodai starter), often referred to as the original starter method for sake brewing. The method is said to have originated in Shoryakuji temple, headquarters of the Bodai sect of Shingon Buddhism in the Bodaisen (Mount Bodai) area of Nara City. [Although its status as “birthplace of sake” is contested.]

After introducing the temple and its history, the article dives into what’s special about bodaimoto on page 2.

For a start, bodaimoto has more lactic acid in the ferment than other starters. Sake brewing – with its double parallel fermentation by kōji and yeast, as any educational organisation will be quick to remind you – also relies to a greater or lesser extent on lactobacilli. [Modern sokujō (速醸, fast-brew) starters involve adding commercially produced lactic acid instead of waiting for bacteria to produce it.] In bodaimoto, lactic acid produced by lactobacilli cuts down the number of competing microorganisms before the yeast gets to work, resulting in a sake starter with high levels of lactic acid.

All this may remind you of another starter method, namely kimoto (生酛). It’s the same principle, but with the key difference that bodaimoto can be brewed in summer as well.

To make a bodaimoto starter, you soak a small amount of boiled rice and put it into a bag, then soak the raw rice to be used for brewing in the water the boiled rice was soaked in. This mixture is then kneaded or rubbed once a day, and by the third day lactobacilli should have increased to the point that the water starts to smell like yoghurt. This acidic water is then used for the moto (酛, starter).

The lactic acid produced by the lactobacilli not only prevents contamination by unwanted microorganisms but also creates a favourable environment for the yeast. Once the alcohol rises to a certain level, the lactobacilli die off and leave a pure yeast culture.

Sounds simple? It is in theory, but in reality there’s a high chance of contamination by mould or other undesirable microorganisms before the lactobacilli produce enough lactic acid. The starter relies heavily on microorganisms and so doesn’t generate an easily repeatable result. So it looks easy but is actually very complicated, which is one of the reasons it fell out of favour compared to kimoto and other methods.

Despite that, a Nara brewery owner and friends set up a Nara Bodaimoto Sake Brewing Research Society in 1996 and there are now a small number of breweries working with this ancient, slightly more risky method.