It is tōji; the shortest day of the year. The sun, which has brought a comforting warmth to the day, sinks below the horizon heralding crisp, biting air and hasty darkness. Steam rises from a cyprus-wood tub, and with it a comforting, citrus scent. Bobbing in the soothingly warm water are dimpled golden fruits, a visual hybrid of an orange and a grapefruit. These zesty orbs, with high concentrations of vitamin C and an oily component consisting of nomilin, are there to guard against colds in the long winter ahead, to treat irritated skin, and to aid circulation while promoting comfort and relaxation. Since the 18th century, the solstice yuzuburo, a bath with the winter citrus fruit yuzu, has been a favourite tradition with Japanese families.

Yuzu is a rare citrus which can grow in regions with winter temperatures as low as -9C, and it fruits in Japan at the beginning of winter. Introduced to the country from China in the 8th century, its seeds have traditionally been used in medicines to treat skin irritations. In culinary terms, lacking in juice and pulp, it is its zest which is employed most. It has a strong, aromatic flavour which is instantly recognisable, and not always popular amongst Japanese children, becoming an acquired taste in later years. It is combined with mirin (rice wine), vinegar, katsuobushi (fish flakes) and kombu (seaweed) to make the dipping sauce ponzu, or with chilli peppers and salt to produce the condiment yuzu kosho. It is added to honey as a sweetener for tea, distilled into vinegar or the liquor yuzukomachi, and used to add a spark to drinks such as non-alcoholic cider. A single shaving of zest atop a piece of sashimi can add a pleasant zing. Chefs in Japan today use it playfully, drawing on its seasonal associations with winter.

In the last 10 years or so, the west have grown familiar with this east Asian taste explosion, although it can be difficult to obtain the fresh fruit and users often make do with bottled yuzu juice. Chefs have employed its powerful citrus bite, adding it to seafood dressings, mayonnaise, fish marinades, custards, jellies, panna cotta and pavlovas. There are several examples of celebrity chefs experimenting with the fruit in their recipes, from Jamie Oliver’s Asian seafood salad with yuzu and sesame dressing and Heston Blumenthal’s yuzu remoulade with barbecued pork chops to James Martin’s deep fried squid with yuzu mayonnaise.  Meanwhile, mixologists use it to give a flavour kick to their cocktails and several craft breweries, including Iki in the Netherlands and Garage Project in New Zealand, have added it as a citrus element in their beers.
March 2nd 2017