|Starting each year on a cold, crisp December morning, a few small tofu shops begin the ancient five-hundred-year-old process by cooking stone-ground soybeans in a cauldron to make a firm tofu. This kata-dofu (hard tofu) is a traditional favorite of high mountain people who prefer its coarse texture and rich taste to "bland, watery, lowland varieties," as they say.
The fresh tofu is cooled in icy well water and skillfully cut into thin slabs. These slabs are placed on bamboo trays and allowed to freeze overnight. The water in the tofu, about 86 percent by weight, turns to ice. The protein, minerals, and other solids congeal into a firm, lacy network. The following morning, workers begin the tedious task of stringing pieces of frozen tofu with braided rice straw. Immediately, workers facilitate the freeze-drying process by hanging the tied frozen tofu from wooden frames in an open shed. There the tofu squares are left to twist and sway in the wind. During the day, temperatures are just warm enough to thaw the tofu and evaporate some of the water. At night, the tofu freezes solid again. This "aging" process is critical, and only temperature and humidity that fall within a narrow range can produce the finely textured, highly absorbent, "snow-dried" tofu that is characteristic of this region of Japan. After about twenty days, the tofu slices are feather-light and bone-dry. Only 10 percent of the original moisture remains, and nature's low-tech drying process is complete.