Why Is Kyushu Miso Sweet? No Sugar Added - Barley Koji Is the Answer

Drink miso soup in Kyushu and you will probably notice it is a little sweet. Plenty of people meet that sweetness for the first time at a hotel breakfast on a trip, or in the kitchen of a friend from Kyushu, and stop to ask about it.

There is no sugar in it. So where does the sweetness come from? From the miso itself, and more precisely from the amount and the kind of koji (the fermentation culture Aspergillus oryzae) that goes into it.

The sweetness comes from how much barley koji goes in, and what it does

Almost all miso made in Kyushu is mugi miso (barley miso). The koji is grown not on rice but on barley or hulless barley, and a lot of it goes in. That is where the sweetness starts.

Trace the sweetness back and you arrive at a single figure: koji buai, the ratio of koji to soybeans. Kyushu barley miso is often brewed at a koji buai of 15 to 20 (15 to 20 parts barley koji to 10 parts soybeans), against roughly 10 for a standard rice miso. That works out to 1.5 to 2 times as much koji. The higher the koji buai, the more starch there is to be turned into sugar. So "barley, therefore sweet" is only half of it. "A lot of barley koji, therefore sweet" is the accurate version.

Barley koji is also said to convert starch to sugar more readily than rice koji. It breaks soybean protein down into amino acids more gently, so sweetness comes forward ahead of savoriness. That is why barley miso reads sweet with no sugar added at all.

Short aging leaves the sugar as sugar

The second reason is the length of the aging. Kyushu barley miso is finished young, at 1 to 3 months, so the sugar the koji made is still there when the miso reaches you.

Miso left to rest for a long time is different: the sugar binds with amino acids and turns into color and savoriness. Hatcho miso, which passes through two summers and two winters, keeps almost no sweetness at all - astringency and acidity lead instead. The sweetness of Kyushu miso is the result of a design decision: a lot of barley koji, finished quickly.

Low salt lets the sweetness show

Kyushu barley miso runs about 9-11% salt; rice miso such as Shinshu (信州) miso runs about 12%. On paper the gap is small, but with more sugar present the salt recedes, and the sweetness you actually taste is larger than the figures suggest.

Sweet without adding anything: the Kyushu design

Households in Kyushu almost never add sugar or mirin to miso soup. It comes out sweet anyway, because the miso is built to let the barley koji do the sweetening. Even in Nagasaki, where sugar arrived through Dejima (出島) and the local cooking runs sweet, the sweetness of the barley miso comes from the koji, not from sugar.

Barley miso and rice miso: what differs

Miso is a fermented food made by adding koji and salt to soybeans. What the koji is grown on is what separates one type from another. Rice koji gives rice miso; koji grown on barley or hulless barley gives barley miso.

Both are called miso, but the grain and the quantity of the koji change the flavor a great deal. Barley miso brings sweetness and a toasty note; rice miso brings clean depth and savoriness. If you want less salt, barley miso; if you want deep savoriness, rice miso. Choosing by purpose is the practical approach.

Why Kyushu settled on barley miso

Barley and hulless barley grow on land that does not suit rice, and Kyushu and the Seto Inland Sea region have grown them for a long time. That is said to be why barley miso, which uses more barley koji than soybeans, became the norm here. Oita, Kumamoto, Nagasaki, Miyazaki, Kagoshima, and Ehime across the water form one continuous belt of barley miso culture.

Alongside the natural sweetness from the barley koji, many breweries here brew at a low salt level, and that is part of why miso soup in Kyushu lands as a gentle sweetness. To a palate raised on rice miso it is a surprise. Here it is simply what miso soup has always tasted like.

Barley miso is not the only sweet miso

Search for sweet miso and most people land on Kyushu barley miso, but other sweet miso exist. Kyoto white miso is the obvious one.

The sweetness comes from somewhere else, though. Kyushu barley miso gets a toasty sweetness from sugar made by the barley koji; Kyoto's Saikyo Miso gets a rounder sweetness from an extreme design - twice the koji, 5% salt. The first arrives with a toasted barley note; the second spreads out and clears. "Sweet miso" is not one thing.

At the opposite end sits Hatcho miso from Aichi, which goes as far from sweetness as miso can. Its koji is grown on soybeans alone and it ages through two summers and two winters, so almost no sweetness survives and astringency and acidity lead. Whether a miso reads sweet or sharp is largely settled by the kind of koji, how much of it, and how long the aging runs.

Sweet Kyushu miso: the benchmarks in Oita, Nagasaki and Ehime

Oita: Fundokin Shoyu, Kizume Koji Tappuri Mutenka Mugi Miso

Fundokin Shoyu, in Usuki (臼杵) in Oita, was founded in 1861. For more than 160 years it has been making the sweet miso of Kyushu.

Its flagship, Kizume Koji Tappuri Mutenka Mugi Miso (生詰麹たっぷり無添加麦みそ), is brewed with more barley koji than soybeans and then packed by the kizume method - no heat pasteurization, so the yeast goes into the tub alive. The gentle sweetness, with no additives, is the taste people from Kyushu remember from home. If you are trying sweet Kyushu miso soup at home for the first time, start here.

Nagasaki: Choko Shoyu, Nagasaki Mugi Miso

Nagasaki Mugi Miso (長崎麦みそ), made by Choko Shoyu in Omura (大村) in Nagasaki, uses only domestic hulless barley for its koji. Hulless barley has a thin skin, which is said to let the koji culture spread through it easily. The miso is never heated after brewing, so the koji and yeast arrive alive. No preservatives, no sweeteners, no colorings.

Nagasaki is where sugar came ashore at Dejima, and the local cooking is sweet. But the sweetness of this barley miso comes from the koji itself, not from sugar. It is the plainest way to taste the answer to "why is Kyushu miso sweet".

Ehime: Gino Miso, Kokusan Iyo no Miso

Kokusan Iyo no Miso (国産伊予のみそ), from Gino Miso in Masaki (松前町) in Ehime (established 1958), is a barley miso that fits a prefecture that grows more hulless barley than any other in Japan. Koji from domestic hulless barley goes in at a higher ratio than the soybeans, salt is held to about 8.5%, and the toasted barley note and natural sweetness both stand out. Iyo (伊予), just across the water from Kyushu, turns out to share the same barley miso culture.

How to use it

• Tonjiru (豚汁) and sweet potato miso soup: the sweetness of the barley miso and of the root vegetables layer together
• Hiyajiru (冷や汁): a chilled miso soup long made in Miyazaki, Ehime and elsewhere
• Miso dengaku (味噌田楽), or a dip for cucumber: eat it close to straight and the sweetness comes through
• Blended into your usual miso: stir a little into rice miso and you gain the toasty note

The more used you are to rice miso, the more the sweet miso soup of Kyushu will land as something new. Start with a single bowl and taste what the barley country makes.

Frequently asked questions

Why is Kyushu miso sweet? Does it contain sugar?

No sugar is added. Kyushu makes mugi miso (barley miso), which uses more barley koji than soybeans - typically 15 to 20 parts barley koji to 10 parts soybeans, a high koji buai. That is 1.5 to 2 times the koji of a standard rice miso, and the enzymes in barley koji keep turning barley starch into sugar. Aging is short, 1 to 3 months, so the sugar stays sugar, and salt is kept low at about 9-11%. The result is a faintly sweet bowl of miso soup.

Why does miso soup in Kyushu taste sweeter than elsewhere in Japan?

Because the miso itself is different. Most of Japan uses kome miso (rice miso), while Kyushu uses mugi miso made with koji grown on barley or hulless barley. Barley koji converts starch to sugar readily, and Kyushu breweries use a high koji buai and low salt, so the same amount dissolved in the same volume of dashi reads sweeter.

What is the difference between barley miso and rice miso?

The grain the koji is grown on. Rice miso uses rice koji; barley miso uses koji grown on barley or hulless barley. Barley koji converts starch to sugar more readily than rice koji, so barley miso tastes sweet even at a lower salt level.

Which barley miso should a first-timer buy?

Fundokin Shoyu's Kizume Koji Tappuri Mutenka Mugi Miso (生詰麹たっぷり無添加麦みそ), from Usuki in Oita, is the benchmark. It is packed by the kizume method, without heat pasteurization, so the yeast goes into the tub alive, and the toasty barley note and the sweetness both stay gentle.

Is barley miso or rice miso better for you?

Neither is simply better than the other. Barley miso carries somewhat more dietary fiber from the barley, and its salt is slightly lower at about 9-11% against about 12% for rice miso. Rice miso, aged longer, is richer in the amino acids that carry savoriness. If you want less salt, reach for barley miso; if you want depth, reach for rice miso. Choose by what the dish needs.