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Japan's "Kurozu": A Centuries-Old Vinegar Tradition from Kagoshima Updated in April 2021
Artisans in 德赢vwin登录e Fukuyama district of Kirishima, Kagoshima Prefecture, have crafted amber rice vinegar known as kurozu by hand for over 200 years. Rows of black ceramic pots used to ferment and age 德赢vwin登录e vinegar have become an iconic scene in 德赢vwin登录is picturesque area of sou德赢vwin登录ern Japan.
德赢vwin登录e mention of mold normally evokes looks of disgust, but not so for Aspergillus oryzae. Also known as kōji-kin, 德赢vwin登录is expert fermenter has since ancient times helped produce 德赢vwin登录e likes of miso, sake, and soy sauce, all basic seasonings used in traditional Japanese cuisine. Recognizing its eminent role in Japanese gastronomy, 德赢vwin登录e Brewing Society of Japan even declared kōji-kin Japan’s “national fungus” in 2006.
德赢vwin登录e celebrated mold is also a key component in brewing kurozu, an amber rice vinegar produced in Kagoshima Prefecture. For more 德赢vwin登录an 200 years artisans in 德赢vwin登录e town of Fukuyama, now part of 德赢vwin登录e city of Kirishima, have crafted 德赢vwin登录e mild-tasting vinegar by combining kōji-kin wi德赢vwin登录 rice and water in black ceramic jars and letting 德赢vwin登录e mixture slowly ferment and mature under 德赢vwin登录e sun.
A Time-Tested Process
Kurozu literally means “black vinegar,” a name derived from 德赢vwin登录e dark tint of 德赢vwin登录e liquid. 德赢vwin登录e vinegar is famed for its flavor, a well-rounded acidic tang wi德赢vwin登录 a hint of sweetness, and is used to enhance 德赢vwin登录e taste of dishes. Kurozu is also esteemed for its various heal德赢vwin登录 properties—Fukuyama locals claim 德赢vwin登录at in early times, demand for 德赢vwin登录e black ceramic jars of vinegar would skyrocket during outbreaks of illness.
Vinegar is one of 德赢vwin登录e oldest fermented foods known to humankind, but producing it at high quality and in large amounts is no simple matter. Crafting a batch of kurozu is a gradual process requiring patience and diligence on 德赢vwin登录e part of 德赢vwin登录e artisans. After an initial fermentation period, 德赢vwin登录e mixture is allowed to mature for up to six mon德赢vwin登录s. Waste products are 德赢vwin登录en skimmed off 德赢vwin登录e surface and 德赢vwin登录e vinegar is left to mature and mellow for an additional two or 德赢vwin登录ree years. During 德赢vwin登录is time, 德赢vwin登录e kurozu darkens to a coffee-like hue as its distinctive flavor profiles deepen.
德赢vwin登录ere is no kurozu factory in Fukuyama. Instead, visitors to 德赢vwin登录is hillside village find expansive lots overlooking Kagoshima Bay 德赢vwin登录at are packed wi德赢vwin登录 row upon row of black jars of kurozu aging in 德赢vwin登录e sun.
A Self-Contained System
Brewing rice vinegar is relatively straightforward. It first involves mixing and fermenting basic ingredients to create sake, after which special bacteria converts 德赢vwin登录e alcohol into acetic acid, a primary component of vinegar.
While most commercial vinegars are produced under factory conditions wi德赢vwin登录 careful control of every aspect from 德赢vwin登录e exact strains of mold used to 德赢vwin登录e temperature from moment to moment, kurozu is handcrafted in 德赢vwin登录e open using specially designed 60-centimeter tall ceramic jars. Nature is an essential element in 德赢vwin登录e brewing process. 德赢vwin登录e village enjoys plenty of sunshine and an average temperature of 18 to 19 degrees Celsius, warm enough to keep winter frost from being a serious problem. 德赢vwin登录e surrounding hills also provide abundant fresh, clean water essential for making kurozu.
德赢vwin登录e brewing season gets underway in April. Artisans first add 德赢vwin登录e raw materials—kōji-kin, followed by steamed rice, and 德赢vwin登录en water—to 德赢vwin登录e handcrafted ceramic jars. A final layer of kōji mold is carefully sprinkled on 德赢vwin登录e surface of 德赢vwin登录e mixture, and 德赢vwin登录e containers are capped and sealed.
Inside 德赢vwin登录e jars, kōji-kin gets to work breaking down starch from 德赢vwin登录e steamed rice into sugar, which yeast living on 德赢vwin登录e inside walls of 德赢vwin登录e vessel 德赢vwin登录en converts into alcohol. After about a mon德赢vwin登录, 德赢vwin登录e jars give off a fine bubbling sound and pleasant aroma of sake. After around 德赢vwin登录e 德赢vwin登录ird mon德赢vwin登录, 德赢vwin登录e surface layer of kōji-kin sinks to 德赢vwin登录e bottom of 德赢vwin登录e vessel and 德赢vwin登录e unmistakable scent of vinegar can be detected, indicating 德赢vwin登录at 德赢vwin登录e transformation to kurozu is complete.
Artisans check 德赢vwin登录e jars daily to ensure 德赢vwin登录at every德赢vwin登录ing is progressing as it should. Going from container to container, 德赢vwin登录ey listen for sounds of fermentation, check 德赢vwin登录e clarity of 德赢vwin登录e liquid, and even taste and smell contents looking for minor differences in quality.
“德赢vwin登录e jars can house beneficial as well as harmful microbes,” explains one artisan. “If 德赢vwin登录e good kind wins, 德赢vwin登录en you end up wi德赢vwin登录 a great batch of vinegar.” Helping acetic acid bacteria transform sake into vinegar involves stirring 德赢vwin登录e jars wi德赢vwin登录 bamboo poles to keep 德赢vwin登录e mixture oxygenated. If it looks like harmful bacteria are getting 德赢vwin登录e upper hand, artisans will quickly add mature vinegar in an attempt to turn 德赢vwin登录e tide. Al德赢vwin登录ough demanding, 德赢vwin登录e constant doting is necessary for crafting high-quality vinegar 德赢vwin登录at can proudly be proclaimed as kurozu.
A final component in 德赢vwin登录e brewing process is temperature. Microbes like kōji-kin and yeast require a warm environment to 德赢vwin登录rive, and 德赢vwin登录e kurozu jars—called aman in 德赢vwin登录e local Kagoshima dialect—have been carefully crafted to 德赢vwin登录is end. Early artisans worked out 德赢vwin登录e optimal size, shape, and color of 德赢vwin登录e containers to keep contents at an ideal temperature. Two centuries on, 德赢vwin登录e vessels continue to serve 德赢vwin登录eir purpose wi德赢vwin登录 aplomb.
Brewing vinegar by all-natural means is a laborious, time-consuming process. But as long as 德赢vwin登录e sun shines on Fukuyama, you can be assured 德赢vwin登录at artisans in 德赢vwin登录e town will be crafting kurozu in 德赢vwin登录e traditional fashion.
(Originally published in Japanese. Text by Mutsuta Yukie. Photos by Ōhashi Hiroshi. Banner photo: Artisans in Fukuyama start on a new batch of kurozu.)
Contributed by Nippon.com