Japan is well known for borrowing ideas and technology from other countries and adapting them to something distinctly Japanese. Black vinegar is one such item.

More than two centuries ago, the village of Fukuyama on the eastern shore of Kagoshima Bay began producing black vinegar using methods imported from China. Refined and developed over the years, the result is kurozu, black vinegar rich in amino and other healthy acids as well as anti-oxidants and other nutrients. And oh, so tasty!

Today there are eight vinegaries in Fukuyama. At the Kakuida Vinegar Brewery, visitors can learn how this delightful brew is produced and what makes it both tasty and healthy. Be sure to finish the visit with a meal in their restaurant, with its wonderful views of Sakurajima, the active volcano that dominates Kagoshima Bay.

The production of kurozu begins quite similarly to sake-making, with rice, water and koji (a fungus that grows on rice). Koji (Aspergillus Oryzae) converts the starch of rice into sugar, promoting fermentation. In fact, before the brew becomes vinegar, it is sake. But by fermenting the mixture longer, the alcohol evaporates, resulting in vinegar.

At Kakuida, they use pure local spring water and organic brown rice. Brown rice is known to be better at producing amino acids. It is said that one reason the villagers at Fukuyama began producing kurozu was the availability of both good water and good rice. There is also a natural yeast in the local air that facilitates the vinegar production.

It takes a year to produce vinegar, but Kakuida ages its vinegar for a minimum of three years, the period they say is “full fermentation”. The result is a deeper, richer color and flavor. The most promising batches may be fermented for five or even 10 years. Baba-san, the host for my visit, scooped vinegar out of a couple of tsubo to show the difference between one year-old vinegar and three year-old kurozu.

The ageing is done in large (54 liter) ceramic pots called tsubo, that are lined up in rows outdoors. Sunlight and the changing seasons also contribute to the fermentation process and final flavor of the vinegar.

Modern vinegar production in factories is done in stainless steel vats, but at Kakuida they are continuing to use traditional tsubo to produce their special kurozu. The pots themselves also contribute to the flavor. That is, after the vinegar is ready, the tsubo are pumped out, washed and used again. Like wine barrels, any residue remaining even after washing improves the flavor of the next batch. The tsubo last about 15 years or five production cycles.

For the first year of fermentation, the tsubo is “closed” with a sheet of paper across the top and then a heavy ceramic lid. After one year, the paper sheet is replaced with a plastic one. Each tsubo is also numbered and dated to facilitate management of the process.

Tsubo are usually black or brown, the dark color best for absorbing sunlight. At Kakuida, the black tsubo usually come from Shiga Prefecture, while the brown ones are produced in Shimane. There are also some brown tsubo imported from Korea. The rows of tsubo are referred to as tsubo-batake (literally, fields of pots)

Kakuida also has a shop where visitors can sample its products and make purchases. (Free shipping to anywhere in Japan for purchases in excess of JPY10,000.) Fruit-infused vinegar (several flavors available) is an especially popular drink (mix with water in a 4:1 ratio). Research has shown that a daily drink of this vinegar can prevent skin cancer. Other health benefits attributed to kurozu include lowering cholesterol, improving digestion and circulation, and detoxifying. Apparently it also contributes to weight loss.

The shop also has a wide variety of salad dressings and other sauces made with kurozu as well as several varieties and ages of kurozu.

It is popular to paint up the tsubo that have become too old to use and they decorate various parts of the building, especially the restaurant. There is even an annual contest awarding prices to the most creative decorators.

Predictably, Kakuida’s restaurant, on the upper floor above the shop, serves dishes featuring their delicious kurozu. The sweet and sour pork lunch special even comes with a kurozu appertif. The grain-and-rice dish was cleverly served in the shape of Sakurajima, with the real thing visible from the window.

Even if you can’t visit Kakuida for yourself, their products are readily available for purchase on the Internet. Between the delicious flavor and the health benefits, you can’t beat it.

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