Hard times

As you’ll have seen in this newsletter and many other places last year, the extreme summer heat in Japan made a lot of rice harder and less soluble than usual. Instagram is currently full of breweries and farmers planting out rice seedlings, and you have to wonder how this year will turn out. 

The Japan News (an English news service by the Yomiuri Newspaper) has a story about the consequences of rice not breaking down during brewing – in this case an excess of kasu, or sake less/cake. To give you an idea of how much more kasu can be produced by harder rice, Takeda Shuzo in Niigata Prefecture posted images of piles of ita-kasu (the flat sheets of kasu removed from automatic pressing machines) asking people to come and take it for free. Their brewing year normally produces 4-5 tons of kasu, but in 2023-2024 it jumped to over 20 tons.

Breweries normally have sales channels for their kasu, which are used in cooking and pickling, but there was no way they could move four times as much by normal methods, hence the call for takers on social media. And the public responded, with every last sheet claimed by mid-March. 

Further north, the Akita Research Institute of Food and Brewing commented that their sake breweries had experienced the same problem, and it seemed to affect brewers nationwide. The Brewing Society of Japan suggest a few options for handling hard-to-dissolve rice, including extending the main ferment for as long as possible, or adding commercial enzymes to the moromi. [I know one brewery that didn’t have a problem, but they credited their very specific local geography for the rice developing as usual. Another we visited last year chose to generate more kasu in order to produce sake with a flavour profile close to their usual one.]

Haruki Takeda, 10th generation owner of Takeda Shuzo, was relieved that none of their kasu went to waste, and hoped it would provide a good opportunity for people to learn about it. In Kyoto, Tama no Hikari went one step further by taking as much pride in their kasu as they do in their sake, and have set up a restaurant that uses kasu in all its dishes.

I’ve already talked about the effect of warmer winter temperatures on traditional cold-weather sake brewing (hello, ice makers in breweries) but a recent article in The Drinks Business magazine about increasing impact on wine fermentation raised another question. Wine is traditionally fermented using yeast found naturally on grape skins, but changing climate conditions are now affecting that microbial population and leading to very different fermentations than winemakers are used to.

Is there a risk to the ambient microorganisms used in sake brewing, mainly lactic acid bacteria but in some cases also yeast? Hitoshi Utsunomiya of JSS said he didn’t think so, as these microbes live a more protected life inside breweries, but said the impact would be felt instead in the selection of cultured yeasts, which traditionally prioritised the ability to ferment in the cold. So who knows, the world of yeast could be about to warm up.

Utsunomiya also mentioned that the issue is being taken very seriously in agriculture, with new rice varieties being developed not only to remain soluble when grown in higher summer temperatures, but also able to mature properly in the heat – immature grains affected 5% of yield in the north of Japan, and up to 20% in areas south of Yamagata Prefecture. [As far as I know, these grains affect the overall grade of the rice (see this handy list of rice grades from Timothy Sullivan of Urban Sake) and would not be suitable to brew with.] There are also experiments to extend the nakaboshi mid-season draining of rice fields in order to reduce methane produced by anerobic bacteria in the soil.

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Brewers Find Ways To Utilize Surplus Sake Kasu (The Japan News by the Yomiuri Newspaper, 19 May 2024, English)
Private correspondence with the Japan Shochu and Sake Makers Association, Brewing Society of Japan and brewery owners/staff
Even fermentation is now being hampered by climate change (The Drinks Business, 15 May 2024, English)
農業で地球温暖化に立ち向かう ～水田からのメタン抑制と高温耐性のイネ育種～ (Science Portal, 30 April 2024, Japanese)

See also Nowhere to run: Sake brewing and climate change on the Sake on Air site