The rise and fall of foam

You’ve probably all heard of Association Yeast, Society Yeast–or, to give it its trademarked name, Kyokai Yeast. The Brewing Society of Japan (Nihon Jо̄zо̄ Kyо̄kai, 日本醸造協会, BSJ) held an online seminar on 24 Oct 2025 to highlight their sake yeast strains, including some brand new ones that are still at test brewing stage. (They also sell yeast for wine, shо̄chū and soy sauce.)

Like everything else in the sake brewing world, the price of Kyokai Yeast increased from Sep 2025. 5 ampoules of foaming yeasts #7 and #9 went from JPY 8,100 to JPY 9,180 (11.3% increase), and 10 ampoules of their non-foaming equivalents went up from JPY 19,440 to 21,600 (11.1% increase).

The first presentation was by Simoi Hitoshi, chairman of the BSJ, who talked about how the history of the BSJ is intimately linked to that of the National Research Institute of Brewing (NRIB). The unusual red brick building on the grounds of the small park where the BSJ operates from today is the brewing laboratory that housed the NRIB when it was initially set up by the Ministry of the Treasury to study brewing science in 1904. The BSJ itself was set up two years later by graduates of the laboratory’s courses (mainly sons of kuramoto) to manage the distribution of pure yeast cultures grown in kōji-jiru (kōji soup). A 100 ml bottle cost the princely sum of 1 yen 80 sen and would have been added to kimoto starters. The ability to concentrate yeast cells led to packaging in 10 ml ampoules in 1967, and the distinctive coloured labels decorated with the yeast line number also date from this time.

As well as the many sake yeast strains listed for sale on their site, the BSJ holds “discontinued” strains, such as #1, and cultures them upon request. The most popular yeast they sell is #901 (the non-foaming version of #9, “Kumamoto yeast”), which sold around 9,500 ampoules in 2024, followed by #701 (the non-foaming version of #7, discovered at Miyasaka Shuzo, makers of Masumi), which sold around 7,500 ampoules. Honourable mention to #1401 with around 3,700 ampoules [I never hear about this one!] and the extravagant #1801 with around 2,700 ampoules. Non-foaming yeast is now much more popular than foaming, which makes up only 11% of their sales. The BSJ is not the only supplier of yeast, and Simoi also pointed out that some brewers blend yeasts and yeast strains provided as slants are not included in the ampoule statistics, so they don’t give a completely accurate picture of what is being used to brew sake today.

There are reasons why brewers prefer non-foaming yeast, including but not limited to having to break up the rising foam to avoid it spilling over the side of the tanks! Mizuo in Nagano Prefecture still use foaming yeast for 98% of their production, in contrast to the 90% of sake on the market made with non-foaming yeast. (Source: Mizuo Instagram account)

The second presentation was given by BSJ yeast specialist Nakahara Katsumi. He pointed out that sake yeasts sold in 10 ml ampoules (now in 10 ml plastic sachets) were originally sampled from successful breweries and are therefore powerful fermenters. This is in contrast to (often but not always) newer yeast strains selected for properties other than fermentation, such as aroma or ability to produce (or not produce) substances of interest, which are sold in plastic bottles that contain a much larger number of yeast cells. Non-foaming yeasts generally have the same properties as the foaming yeast they were isolated from, but effectively increase tank capacity by 20-30% as they produce so little foam. The yeast also spends more time in the moromi (instead of joy-riding on the foam) which actually speeds up fermentation.

He showed a photo of two large jars side-by-side, both half-full of rice, kōji and water, one with #7 yeast (foaming) and one with #701 yeast (non-foaming). Why show something so basic? Because he expected that some people watching would never have seen foaming yeast. That’s how unpopular it has become. He also pointed out that the recommended quantity of yeast to add to the starter is based on non-foaming yeast needing to out-compete any foaming yeast left in the environment, but breweries that have never used foaming yeast can get away with the smaller amounts given for foaming yeast (as the non-foaming yeast has no competition).

Nakahara described many of the older yeasts (or newer yeasts developed from them) as powerful fermenters that do well in high concentrations of sugar and produce sake with a stable aroma that ages in a predictable way. On the other hand, many newer yeasts chosen for properties other than fermentation tend to be weaker fermenters that create sake with unstable aromas. He also touched an issue arising from hot weather (climate change) where rice becomes harder and does not break down in the main ferment: one common countermeasure is using high-amylase strains of kōji, but the resulting burst of glucose could cause yeast to produce unexpectedly high levels of aroma. His suggested countermeasure for the countermeasure is mixing aromatic yeast strains with less aromatic ones, but this requires a lot of experience as some yeasts out-compete others (so adding a 50/50 split of yeast strains in the starter would not necessarily result in a 50/50 split in the moromi).

The session closed with two short presentations, the first from Sakai Shuzo in Yamaguchi who reported on brewing with high-malic acidity yeast #28 in combination with differing amounts of white kōji and further variation created by high-temperature saccharification (kō-on tōka, 高温糖化) and kimoto starters. Akebono Shuzo in Fukushima finished with a short account of brewing with new yeast Ka8, which is designed to minimise production of components that cause hine and hopefully protect sake throughout the export process. They hadn’t been using it for long, but said it was very easy to use, similar to #1801 in how it fermented and resulting levels of amino acids and acids, but with significantly less aroma.

Closing words from BSJ vice-chair Goto Nami (formerly of the NRIB) included a warning that red yeast (a terrible fermenter popular for producing red compounds that stay in the rice solids) had sold out so they would mass-culture more in the new year.

And an announcement on 6 Nov 2025 confirmed that Ka8, previously only available as a slant, will go on sale in large-capacity plastic bottles in February 2026 alongside other yeasts chosen for properties other than fermentation. Brewers were asked to fax their orders in in good time!

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Source: Brewing Society of Japan yeast webinar, 24 Oct 2025

More foaming yeast in action, this time at Kikkawa in Kanagawa. (Which yeast? Who knows, they didn’t add any so it’s whatever is living in the brewery building…) (Source: Kikkawa Jozo Instagram account)