Yuzu is a citrus fruit originating from East Asia, it has a sharp and zesty aroma that when added to products has an uplifting effect on the mind, is antibacterial and brightens the skin.
The fruit of the yuzu is like a cross between a sour mandarin and a grapefruit in size, taste and smell. It can be either yellow or green depending on the degree of ripeness. They are very aromatic and is most famous for being an integral ingredient in the citrus-based sauce ponzu. Yuzu vinegar is also a popular product of yuzu fruit.
Yuzu fruit are used in Japan as part of a traditional winter bathing ritual. The whole fruits are floated in steaming baths at winter solstice to ward off illnesses such as flu and colds in the coming year. The sharp and zesty fragrance helps energise the body and mind.
In some parts of Japan, it is traditional at the winter solstice (tōji) to take a yuzu-yu or yuzuyu (a yuzu fruit bath) – this is a tradition which dates to the 18th-century. The yuzu-yu is a hot bath with whole yuzu fruits floating in it.
A study by Matsumoto, Kimura, and Hayashi found that ‘short-term inhalation of fragrance from yuzu essential oil significantly decreased heart rate’ which may indicate that yuzu fragrance can help ‘alleviate negative emotional stress’. This positive effect on tension was seen after a ten-minute inhalation of the aroma, which lasted up to thirty-five minutes later. Another study found that inhalation of yuzu the night before a major surgery allowed patients to fall asleep more easily, helping with anxiety.
In Japanese cooking, yuzu is also used for the zest of its bright yellow peel in order to create delicate aromas in dishes like clear soups. These would be served in a bowl with a lid, so that the aroma contained in the steam can be breathed in fully when the lid is taken off – the ingredient creating that effect is called suikuchi, and some examples of suikuchi other than yuzu are ingredients such as ginger or wasabi. Yuzu juice might also be used in order to prepare dips or marinades.
From a 2014 article by Nile and Park which collated previously studied benefits of yuzu: ‘Yuzu fruits possess significant amount of bioactive compounds that can influence human health-promoting effects, including antioxidant, anti-inflammatory, cardioprotective, anticarcinogenic, antiallergic, antiplatelet, antiviral, antibacterial, and antifungal activities.’ The antioxidant benefits come from yuzu’s redox properties, especially from its high levels of Vitamin C, which adsorb and neutralize free radicals. As an antimicrobial, it reflects other uses of citrus oils like lemons, limes, and grapefruit.
 Tamaki Matsumoto, Tetsuya Kimura and Tatsuya Hayashi, ‘Aromatic Effects of a Japanese Citrus Fruit—yuzu (Citrus Junos Sieb. Ex Tanaka)—on Psychoemotional States and Autonomic Nervous System Activity during the Menstrual Cycle: A Single-Blind Randomized Controlled Crossover Study’, BioPsychoSocial Medicine, 10 (2016), 11.
 Matsumoto, Kimura and Hayashi.
 M. Sawamura and others, ‘Functional Activities of Japanese Yuzu Essential Oil’, Jpn J Aromather, 9 (2009), 55–65
 Richard Hosking, A Dictionary of Japanese Food: Ingredients & Culture (Tuttle Publishing, 2014), pp. 133, 159, 211.
 Shivraj Hariram Nile and Se Won Park, ‘Bioactive Components and Health-Promoting Properties of Yuzu (Citrus Ichangensis × C. Reticulate)’, Food Reviews International, 30.2 (2014), 155–67.