Japan — yuzu cultivation primarily in Kochi Prefecture, Tokushima, and Ehime; believed to have originated in China and Korea; cultivation in Japan documented from the Nara period; the Toji (winter solstice) yuzuyu bathing tradition from the Edo period
Yuzu (柚子, Citrus junos) is Japan's most important citrus fruit — not for its juice (which is quite sour and produced in relatively small quantities per fruit) but for its extraordinary aromatic complexity. The rind contains volatile essential oils with a character unlike any other citrus: simultaneously lemon, mandarin, grapefruit, and something uniquely floral, spicy, and Japanese. Yuzu is used exclusively for its rind and juice rather than eaten as a table fruit. Applications: suimono garnish (a strip of zest cut into a leaf or pine-needle shape); ponzu sauce base; yuzu kosho fermented condiment; yuzubath (yuzuyu) where whole yuzu is floated in the bath on the winter solstice (Toji) for aromatherapy and warming; yuzu wagashi; yuzu sake; yuzu miso; and in modern pastry as a premier citrus aroma.
Intensely aromatic — simultaneously lemon, mandarin, floral, spicy, and something uniquely Japanese; the fragrance alone transforms a suimono from technically excellent to memorably beautiful
Yuzu zest is prepared in two ways for different results: thin julienne (for soup, topping, and fresh uses where the whole strip is visible and bit into), or fine grating (for sauces, dressings, and incorporation into batters where aroma distribution throughout the preparation is desired). For soup use: the strip must be cut precisely — approximately 4cm × 0.3cm, no pith, the zest side facing up on the soup surface. The aromatic compounds in yuzu are extremely volatile — add zest at the last possible moment before serving and never heat the zest directly.
Freeze fresh yuzu juice in ice cube trays (November–December peak harvest); the juice freezes excellently. Freeze zested yuzu skin flat on parchment then store in sealed bags — frozen zest grates extremely well and retains its character for months. The best yuzu comes from Kochi Prefecture (the largest producer), with Tokushima and Ehime also producing significant volumes. Yuzu honeybu (yuzu marmalade) is an excellent pantry shortcut — dissolve in warm water for an instant yuzu drink, or use as a component in ponzu sauce.
Using bottled yuzu juice as a substitute for fresh yuzu rind — the juice preserves some flavour but completely lacks the fresh zest's aromatic complexity. Grating too deep into the white pith, which adds bitter compounds. Heating yuzu zest, which destroys the most volatile aromatic compounds. Treating yuzu as a simple lemon substitute — the aromatic profile is sufficiently distinct that the substitution changes the dish's character completely.
Tsuji, Shizuo — Japanese Cooking: A Simple Art; Murata, Yoshihiro — Kaiseki; Hosking, Richard — A Dictionary of Japanese Food