Chris Pearce
Hawai‘i Herald Columist

Imagine yourself a brewmaster at a sake brewery in central Japan. Tottori Prefecture, let’s say, or perhaps Gunma. You’re checking the condition of the fermentation in the tanks when you suddenly get the shock of your life. Instead of the rambunctious, frothy activity you expect as carbon oxide pushes up through the dissolving rice nutrients to produce a heady foam, there is . . . nothing. Bubbles of escaping gas rise to the surface, and there’s a quiescent layer of foam, but for all intents and purposes, it just looks dead to you. The sake has been contaminated by outside bacteria! The fermentation is not happening! This tank is going to have to be quarantined and destroyed before it affects the rest of the year’s production!

That’s pretty much how brewers viewed awanashi kobo, or non-foaming yeast, when it made an appearance, which, thanks to its extreme rarity, was hardly at all. At a time when there was no refrigeration, when there were no certified yeasts, when scientific brewing practices were not widely applied, there were many ways that sake could go bad. A simple lapse in hygiene — or a brewery worker bringing a natto musubi to work — could result in an infestation of lactic-acid producing hiochi bacteria that could put a brewery out of business. Or, when you put your freshly bottled sake into a hot water bath to pasteurize it, what if the temperature isn’t right? Spoilage is a real possibility. For the brewers of old, and well into the postwar years, brewing sake was fraught with peril. That scary, apparently non-fermenting sake with no froth — get it out of here!

And yet, for scientists in Japan, the mysterious non-foaming yeast exerted an attraction.

Dr. Hiroichi Akiyama, whose book, “Sake,” was published in English translation in 2010 and contains many interesting facts not available from other sources, headed the research. Kozo Ouchi, a co-author of some of Akiyama’s published papers, laid out the background for this effort in “A History of Non-Foaming Yeasts,” which appeared in the April 2010 edition of the Journal of the Brewing Society of Japan.

His account states that in 1916, Genjiro Takahashi of the Hiroshima Tax Office identified a non-foaming yeast and was able to isolate it and then brew a small experimental tank of sake. However, there was no effort to apply this knowledge to commercial brewing. Sporadic appearances of non-foaming yeast were reported over the years, including one in Niigata in 1931, but were regarded as no more than curiosities.

Then, according to Ouchi, in 1963, Akiyama obtained a sample from a brewery in Shimane Prefecture, isolated the non-foaming yeast and published his findings in 1965. This yeast, while useful for research purposes, was never actually used to make sake. In large part, this was due to the fact that sake was on a roll in Japan at the time, with the breweries producing huge amounts and selling it with no difficulty. There was no need for “innovation.” It wasn’t until 1971 that Akiyama and his research team finally succeeded in propagating a non-foaming yeast in the laboratory that could be used to make marketable sake.

Meanwhile, in Hawai‘i, Honolulu Sake Brewery brewmaster Takao Nihei had been using non-foaming yeast on a daily basis since 1959. Far from being unsettled when it made a surprise appearance at his brewery, he immediately collected a sample and took it to the small laboratory next to his office.

Looking at the sample slide under a microscope, he was able to determine that there were no bacteria that might have halted the fermentation. In addition, the alcohol percentage was normal and there was no off-flavor or bad aroma.

Drawing on his brewmaster’s intuition, honed during visits to regional breweries and also from making sake himself at the research institute, he decided that the fermenting moromi (mash) in the tank, while producing little foam, was essentially healthy. Taking a sample, he prepared a starter culture, or moto, and then made a small-scale test run.

This was a success. And not only was it a success, the non-foaming yeast seemed to work especially well with the California rice used to make “Takara Masamune” and “Takara Musume,” Honolulu Sake Brewery’s two labels.

For Nihei-san, this discovery meant that it was no longer necessary for workers to get up in the middle of the night to scrape the foam off the top of the sake vats — although he roused himself every night at 11 p.m. from his home in Pauoa Valley and looked in on them every night without fail. He could at last achieve his goal of a 40-hour work week for the brewery workers, as required by the state of Hawai‘i labor laws.

Right at the time he made his discovery, Dr. Kei Arima from Tokyo University happened to be visiting Hawai‘i. He was astonished by Nihei-san’s discovery and contacted Dr. Akiyama, who, by then, was the director of the National Research Institute of Brewing. “I visited Nihei-san and it’s incredible. He’s using non-foaming yeast to make sake. There’s no need for a machine to remove the foam.” He sent a sample from Honolulu Sake Brewery to the institute, where it seems to have remained untouched for a number of years.

Dr. Akiyama is generally credited with the “discovery” of non-foaming yeast, although, clearly, Nihei-san was the actual pioneer. With the full resources of the research institute at his disposal, Akiyama was able to experiment and fully document his findings in academic publications. A frequent co-author of his papers, Chieko Kumagaya had discovered a method for separating foaming yeasts from non-foaming ones, and it was this, rather than a fortuitous discovery on the brewery floor, that led to the team’s success.

The usual technique for developing a new yeast was to take an existing one and subject it to ultraviolet radiation. This would cause a new node with different characteristics to grow from the yeast “parent.” By cultivating hundreds of these irradiated yeasts, researchers could gradually home in on those with advantageous characteristics. The problem with this was that the new yeast would often lose the characteristics that had made its parent desirable in the first place.

As a result, most researchers stuck with the microscope, time-consuming and tedious as it was to identify a mutant yeast that appeared different from those in the mother culture. One thing researchers did notice is that the cell wall of the foaming yeast seemed softer than the more clearly defined wall of non-foaming yeast cells. But this wasn’t really definitive. The yeasts were identical in every other way.

In the end, it was the microscope that provided a solution to the problem. One day, when preparing the yeast samples, some air bubbles got inadvertently mixed in with the sake foam on the microscope preparation slide. In terms of laboratory practice this was a big mistake. But the researchers were astonished to observe that the foaming yeasts attached themselves to the air bubble, while the non-foaming ones floated free. With this discovery, all the technicians had to do was mix air bubbles in with sake foam and then separate out the non-foaming yeasts. Typically, they would amount to 3.5 percent of the total.

In due course, Akiyama’s team perfected a non-foaming yeast for Association No. 7, one of the most widely used yeasts both then and now. Ouchi writes that it was successfully tested at various breweries around Japan and then went into wide usage. Soon non-foaming varieties of the other Association yeasts appeared. Today, brewers can purchase over twenty different yeasts from the Brewing Society of Japan, evenly split between foaming and non-foaming.

It’s a great story, and the only thing missing in the official account is a full and honest recognition of Takao Nihei’s contribution. In his article, Ouchi has this to say: (1) the Hawai‘i yeast produced a small amount of foam and so it can’t be considered a non-foaming yeast; (2) there is no evidence of any brewery outside Hawai‘i using it; and (3) Nihei-san was mistaken in thinking that the Hawai‘i mutant yeast was an offshoot of Association No. 6 — instead it was Association No. 7. Taken together, it’s hard to regard these comments as anything other than an attempt to discredit Takao Nihei and establish Akiyama and his colleague Ouchi as the true “discovers” of non-foaming yeast, despite the fact that Nihei-san used it to make sake day after day for 10 years before they managed to do it once.

Perhaps the best perspective on this is provided by Yoshihiko Nishioka, a former student of Dr. Kumagaya and now the brewmaster of Seitoku Brewing Company. Here’s what he has to say. “Sake brewing is a traditional industry, and it’s quite conservative about adopting new practices. Nihei-san, with his brewery experience and intuition, created a fresh vision for brewers and gave them the courage to pursue it. If I had been making sake back then, and didn’t know about Hawai‘i’s success, I would never have dared to use a non-foaming yeast.”

“Researchers document their experiments and publish them in academic publications. This becomes the historical record and is widely accepted. However, I take issue with Ouchi when he implies that the Hawai‘i yeast isn’t really awanashi kobo. We work out on the brewery floor, not in research laboratories. For us, if the fermentation concludes without overflowing the tank, it doesn’t matter whether it’s non-foaming or low foaming: it’s awanashi kobo.”

Chris Pearce is a founding member of Hawai‘i’s Kokusai Sake Kai (International Sake Association) and was instrumental in establishing the U.S. National Sake Appraisal. He coordinates the annual “Joy of Sake” events held in Honolulu, Tökyö and in cities on the continental U.S.


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