Kaiire is the process of stirring the moromi. Evenly stirring the sticky mash requires masterful technique.

Soybeans are rich in high-quality protein and fat. They also contain a good balance of carbohydrates, vitamins, minerals, and other nutrients. A favorite “super food” of health-conscious eaters, soybeans are increasingly popular as an ingredient in meat substitutes around the world.

The now trendy soybean has long been commonplace in Japan. With their plenteous protein, soybeans were a good fit for Japan’s vegetable-based diet, which could have easily fallen short on this essential nutrient. In addition to boiled and roasted soybeans, the Japanese dinner table is filled with soybean-based foods processed in a variety of different ways. Miso, tofu, and natto fermented soybeans are all typical examples. The most important of all, however, is soy sauce. It is no exaggeration to say that Japanese food without the flavors of soy sauce is impossible to imagine.

Soy sauce is thought to have originated in the misomaking process introduced by Zen monks in the 13th century. Repeated innovation and improvements have perfected soy sauce into the reddish-black, aromatic liquid we know today. To this day, soy sauce is still made using traditional methods in its birthplace of Yuasa-cho in Wakayama Prefecture.

A mixture of boiled soybeans and roasted, crushed wheat is inoculated with malted rice, then kept at a constant temperature to allow the koji mold to ferment the mixture for three days. Salt and the liquid from the boiled soybeans are added to this mixture to make the base for soy sauce, a thick mixture called moromi. The moromi is placed in wooden barrels to further ferment for more than a year and a half. During this fermentation, a key process called kaiire is employed to encourage fermentation. This involves stirring the viscous mixture with a long-handled paddle called a kai. With no air conditioning in traditional soy sauce breweries, the frequency and timing of the kaiire is adjusted according to the condition of the moromi, as temperatures fluctuate day to day.

Once the moromi has matured, it is poured into a straining cloth and squeezed; the sauce comes out and leaves oil, lees, and other impurities behind. Then, after a final heating, the soy sauce is ready. This heating process stops the fermentation and releases the distinctive aroma of the sauce.

Soy sauce made with high-quality soybeans using this time-consuming method is rich, mellow, and bursting with unmistakable umami flavor. Everyone should try the real deal at least once!