TATSUNO, Hyogo - Soy sauce, shoyu in Japanese, is an indispensable flavouring in washoku Japanese cuisine. One variety is usukuchi shoyu, which is lightly coloured and has a delicate aroma, effectively flavouring ingredients without spoiling their original colour or taste.
To learn more, I recently visited Suehiro Shoyu K.K., a time-honoured shoyu maker in Tatsuno, Hyogo Prefecture, the birthplace of usukuchi shoyu.
After about a 90-minute JR train ride from Osaka, I arrived at Hontatsuno Station in the city. Its main urban area stretches all the way to the Ibogawa river, as if to meet its abundant flow. This is the location of Suehiro Shoyu, established 135 years ago.
Usukuchi shoyu was first manufactured in the city during the Edo period (1603-1867). Ordinary koikuchi shoyu is dark in colour, but usukuchi shoyu is a light reddish brown.
"The riverbed water of the Ibogawa, which is used to produce our shoyu, contains very little iron. Iron makes shoyu dark. So it's suited for manufacturing usukuchi shoyu," said company president Takuya Suehiro, 54.
In its early years, usukuchi shoyu became popular in Kyoto and Osaka, where the colors and other visual elements of food were well appreciated, Suehiro said. It eventually spread to other regions as well.
In addition to having a light colour, usukuchi shoyu is defined by its salt content, which accounts for 18 per cent to 19 per cent of its weight, according to the Japanese Agricultural Standards. Koikuchi dark soy sauce has 16 per cent to 17 per cent salt, meaning that usukuchi contains about two percentage points more. During the manufacturing process, about 10 per cent more salt is used for usukuchi.
To manufacture shoyu, steamed soybeans and roasted wheat are crushed then blended with seed malt, or tane koji.
The mixture is fermented for two nights. When its surface becomes slightly yellow, saltwater is added, and the concoction is left for two to three months in a storehouse. The process takes longer in winter.
The Yomiuri Shimbun To make usukuchi shoyu, a worker at Suehiro Shoyu K.K. in Tatsuno, Hyogo Prefecture, spreads moromi evenly before wrapping it in cloth to prepare for pressing. This results in moromi, or fermented grain slurry, which is finally pressed to collect the liquid that is soy sauce.
"If the salt concentration is high, it inhibits the growth of koji mould and makes the shoyu colour light," Suehiro said.
When I entered the storehouse, the moromi was just starting to be pressed.
I saw an employee spread a cloth onto a square wooden frame about 80 cm long on each side, then place about 10 liters of light brown moromi on the cloth, spreading it evenly. She folded the cloth around the moromi. A large quantity of moromi was wrapped the same way a number of times, and by the end, dozens of bundles were stacked in piles.
When the stacked moromi begins seeping liquid as a result of the weight, a thick board is placed on top of it and pressure is applied. Continuously pressed for a week until it has been flattened like a board, the moromi's umami savory flavour is retained in the shoyu liquid.
Fresh usukuchi shoyu doesn't have the strong flavour characteristic of koikuchi shoyu. When I sampled it, it tasted mild and even sweet.
I asked Shinichi Yamamoto, 47, the fifth-generation operator of the local inn Katashibodake no Yado Umetama, to make some dishes using usukuchi shoyu.
Yamamoto made nyumen, a dish of somen thin noodles that is a regional specialty in warm broth. The broth is a richly flavoured stock made from dried bonito flakes and kombu seaweed, to which usukuchi shoyu is added.
He also prepared stewed akamebaru, a type of rockfish, which had been caught off the coast of the city and brought into a local port. The fish is placed on kombu in a pan for stewing. Generous amounts of sake are used, and some salt and usukuchi shoyu are added to flavour it. The resulting stock is a light gold colour. It tasted so mild that I could have consumed an entire bowl.
"[If you use usukuchi shoyu,] the colour of kombu broth changes very little. It doesn't spoil the flavour of the other ingredients and rather brings out their original taste," Yamamoto said.
Suehiro Shoyu sells various types of usukuchi shoyu. The company's website (www.suehiro-s.co.jp) offers such products as a low-sodium type called "Usu Murasaki," which costs ¥540 (S$6.40) for a 100ml bottle, and "Usukuchi," which is priced at ¥507 for a 500ml bottle, both including tax.
The Usukuchi Tatsuno Shoyu Shiryokan, a museum operated by Higashimaru Shoyu Co., displays various tools and other items related to the history and manufacturing process of usukuchi shoyu. Higashimaru Shoyu is also headquartered in Tatsuno.