"Jar-brewed kurozu: the amber vinegar raised in the \"jar fields\" of Fukuyama, Kagoshima"

Plenty of people know the name kurozu, or black vinegar, and would still hesitate if asked how it differs from an ordinary rice vinegar. It is often taken for a vinegar that is simply darker, but there is a reason for that amber color.

What makes the difference is the method, and the time given to it. Among those methods, the jar brewing handed down in Fukuyama (福山) in Kagoshima is known as a rare one anywhere in the world.

A year inside a jar: the jar fields of Fukuyama

In the town of Fukuyama in Kagoshima, looking out over Kinko Bay, a distinctive way of making vinegar has carried on since the late Edo period. Earthenware jars called aman-tsubo (アマン壺) stand outdoors, and inside them vinegar is brewed from nothing but rice, rice koji and groundwater.

The sight of those jars in rows is called a tsubobatake (壺畑), a "jar field," and it is part of the scenery of Fukuyama. What marks this method out is that several processes - saccharification, alcohol fermentation, acetic fermentation - proceed at the same time inside one jar.

It is the mild climate of Fukuyama that makes long outdoor fermentation possible at all. The character of the place is, in effect, one of the makers.

Why it turns amber

Kurozu takes on its deep color because, over the long aging of a year or more, amino acids and sugars react with each other slowly.

That aging changes the taste at the same time. The sharp catch of a freshly brewed vinegar withdraws, and what grows in its place is round and full. Rich in amino acids, it also carries a depth behind the sourness that belongs to a long-aged kurozu.

Sakamoto no Kurozu Tenju: from the jar fields of Fukuyama

The house keeping this jar brewing going is Sakamoto Jozo in Fukuyama. "Sakamoto no Kurozu Tenju" is an amber kurozu fermented and aged for over a year in jars standing outdoors.

Rice, rice koji, and groundwater. The ingredients could hardly be simpler, but time and the work of nature give them a deep flavor. Do not hurry; wait. That stance is reflected directly in a single drop from the jar fields.

Ways to enjoy kurozu

• Cut 5 to 7 times with water, hot water or soda, as a daily glass
• In sweet-and-sour pork or nanban-zuke, where the acidity pulls together roundly
• Combined with oil as a dressing
• With honey, for a drink that goes down easily

Try it diluted first and the difference from an ordinary vinegar is unmistakable. It is a drop in which you taste, directly, a year spent inside a jar.

Frequently asked questions

How does kurozu differ from an ordinary rice vinegar?

The big difference is the time given to aging. Where a typical rice vinegar is finished in a short span, the kurozu of Fukuyama in Kagoshima ferments and ages for over a year inside jars standing outdoors. Over that long aging, amino acids and other components are said to build up, the color turning amber and the taste round and free of edges.

What is a tsubobatake, or "jar field"?

It is the landscape particular to the town of Fukuyama in Kagoshima: rows upon rows of earthenware jars, called aman-tsubo, standing outdoors with vinegar brewing inside them. Each jar holds nothing but rice, rice koji and groundwater, and ferments slowly with the help of the sun's heat. Open-air jar brewing on this scale is rare anywhere in the world.

How should I use kurozu?

Cut it 5 to 7 times with water, hot water or soda for a daily glass. In cooking, use it in sweet-and-sour pork, nanban-zuke or a dressing, where its round, edgeless acidity pulls a dish together. Because the acidity is soft, drinking it with honey is another approach worth trying.