In a gunmetal gray third-floor lab at Tokyo University of Agriculture, assistant professor Takayuki Kazuoka—the foremost sake yeast researcher of his generation in Japan—and his students are engaged in a high-tech hunt for sake yeast. Their focus is on isolating new flower yeasts cultivated from Japan’s native flora and never before used in sake production.
For Professor Kazuoka and his students the hope is that this research might spur the revival of a once-vibrant, and more diverse, sake brewing tradition—one that many of their families have practiced for generations. For the atostugi, or heirs, their own careers as future presidents of breweries are on the line.
The numbers they face are stark: Only 80 years ago, there were approximately 4,000 sake breweries across Japan, the bulk of them family-run operations. Today, Professor Kazuoka estimates there are perhaps 1,200 breweries certified to make sake, but that only 800 or 900 of those actually still do. With the loss of each brewery, the strains of yeast specific to that brewery vanish along with it. Even more vexing from the sake lover’s point of view is the narrowing of the rich variety of flavors and aromas that Japanese sakes once exhibited. It’s hard to imagine when you consider today’s sake flavor-aroma bandwidth, which is limited by the fact that most breweries are using the same or similar varieties of commercial yeasts.
The tradition Professor Kazuoka and his students are trying to keep alive is an ancient one. Sake making, at its most primitive, dates back to the 1st century BC. By the 12th century it was being produced at Shinto shrines and Buddhist temples where the methods used today were beginning to be developed: inoculating steamed rice with Aspergillus oryzae mold to break down starches into sugar, the creation of a seed mash, lactic acid fermentation (or later, the addition of brewing-grade lactic acid), filtration and usually pasteurization. By the beginning of the 18th century, sake was so popular that in Edo (as Tokyo was formerly known) annual per capita sake consumption reached 54 liters. By 2010 that number had fallen to 4.6 liters per capita and is even lower today.
According to Kazuoka, there are now 30 breweries in Japan that are making sakes with flower yeasts he’s isolated at the university. Raifuku Brewery in Ibaraki Prefecture uses eight flowers yeasts, including strains from the pink dianthus and sunflower. Others, with the help of the university, are looking beyond flowers and to ancient sake yeasts lost to time. At Wakatakeya Brewery in Kurume, Kyushu a junmai called Debut is made using the first strain of yeast isolated in 1895.
In 1895, sake yeast was isolated for the first time, and a few years later the government-affiliated Brewing Society of Japan began collecting yeast strains from the tanks of highly regarded sake breweries and making them available to sake makers across the country. Thanks to a standardization of sake styles and flavors during the midcentury, there are now only 20 of these official “brewing society yeasts,” a mere seven of which constitute the majority of yeasts used for sake making today. The question now is how to find the diversity and greater range of flavors that were lost during this period of homogenization.
While some have set their sights on different rice or mold varieties to answer the question, Professor Kazuoka is convinced that flower yeasts will also create a sort of diversity altogether new to sake. However, finding these yeasts among the flowers native to Japan is a time-consuming and costly process. Professor Kazuoka’s lab at Nodai (as the agricultural university is known) has isolated 20 flower yeasts from all over the country and has spent as many years hunting for them. The payoff is that they generate flavors not only unique between them, but “completely different” from those made using conventionally available yeasts.
“In Japan, we have seasons ranging from very cold to tropical,” Professor Kazuoka points out. With a diversity of flowers to match each season and microclimate, he imagines the day when “breweries can use flowers from their own villages” to make sake.
According to Kazuoka, there are now 30 breweries in Japan that are making sakes with flower yeasts he’s isolated at the university. Raifuku Brewery in Ibaraki Prefecture uses eight flowers yeasts, including strains from the pink dianthus and sunflower, while other notable breweries like Amabuki Brewery in Kyushu Prefecture, Tenju Brewery from Akita Prefecture, Tenryo Brewery in Gifu Prefecture, Rihaku Brewery in Shimane Prefecture and Tajima Brewery in Fukui Prefecture are all experimenting with different flower yeasts.
Others, with the help of the university, are looking beyond flowers to ancient sake yeasts lost to time. At Wakatakeya Brewery in Kurume, Kyushu, a junmai called Debut is made using the first strain of yeast isolated in 1895. The story goes that a Tokyo Nodai professor was in possession of a batch that had been kept frozen for over 100 years; he offered samples only to Wakatakeya’s master brewer, a former student, and to two other breweries.
Apocryphal as the tale of the yeast’s origin may be, Wakatakeya president Hironobu Hayashida says that when he first tasted Debut, he was shocked at how earthy and complex it was, and how wildly different it was from modern sake. “Sake has evolved to have a clear taste,” he says. But in the old days (his family brewery was founded in 1699), he adds, “sake had more body and there was more variety.”
Talk to anyone in Japan’s sake industry, and the subject will turn to how to initiate new drinkers to this ancient brewed beverage as the industry struggles to hold its own not only against the ever-popular shochu, but foreign wine and spirits as well. While the focus of Professor Kazuoka’s lab is on flower yeasts, he knows that any innovation in the industry that widens the depth and variety of available sakes is of great value. “If there is only one style consumers will only know that,” he says. “My hope is that we’ll have yeasts of all different flavors, and rice of all different kinds. I want to have all of them.”