Takuan-zuke is a pickle and is referred to as daikon radish preserved in rice-bran and salt.
It is also known as 'takuan' or 'takuwan.'
According to the traditional recipe, first, daikon radish is sun-dried or air-dried until it is limp or soft enough to bend into a circle and then it is covered with the mixture of rice bran, salt, and the other ingredients including kelp, chili peppers and bark of diospyraceous kaki to add flavor. If no coloring is used, takuan is pale brown in color but, in general, turmeric or gardenia is used to color takuan yellow. With respect to a large majority of takuan-zuke that is distributed today, instead of hiboshi daikon (sun-dried daikon radish), shio-oshi daikon (salt-cured daikon radish) or toshibori daikon (sugar-cured daikon radish), the daikon radish which has been salted or soaked in syrup to reduce its water content is often used. As a result, that takuan-zuke has a different texture from that of takuan made by the traditional method. Some of the takuan-zuke is seasoned with liquid containing various seasoning including sweetener and flavor enhancer in addition to being processed with artificial food coloring. This is in part as a consequence of changes in consumers taste to prefer low sodium pickles over the years, but on the other hand, there have been some feedback mainly from the older consumers on the takuan-zuke in recent years, which seems to be a product of a food engineering process, that it is sweet and has unpleasant texture. Many people expressed their longing for the good old salty takuan that they ate in olden days according to their feedback.
According to one explanation, it was invented by Sosho TAKUWAN as legend goes but it has remained unsubstantiated and there is a heresy on this account.
There is another explanation that takuan-zuke was originally referred to as 'jakuan-zuke' meaning 'a pure thing' but, with Sosho TAKUWAN coming into the picture, it became commonly accepted that 'jakuan' evolved to 'takuan' and then 'it was invented by Takuwan Osho priest.'
There is also another explanation that 'takuwae-zuke (pickle reserve)' turned to 'takuan-zuke.'
At Tokai-ji Temple (Shinagawa Ward, the Metropolis of Tokyo) built by Sosho TAKUWAN, there is a legend saying, "Takuan-zuke was originally a nameless pickle but when served takuan-zuke during his visit to the temple one day, Iemitsu TOKUGAWA enjoyed it so much that he said, 'If it has no name, call it takuan-zuke.'"
By the way, at Tokai-ji Temple, takuan-zuke is referred to as "Hyappon" based on their belief that it is discourteous to use the name of Zenji without an honorific.
When aged, takuan made by using the traditional recipe with sun-dried daikon radish can be soaked in water to remove salt and then can be used in cooking such as pan-fried takuan or takuan cooked in sauce.
They often serve 2 slices of takuan as one of the side dishes at Japanese restaurants and it is said that this custom of offering 2 slices of takuan began in the Edo Period. In the Edo Period, when the world revolved around samurai takuan was an essential old standby side dish but it was a taboo to serve samurai either one piece or three pieces of takuan in those days.
The reason for this was that if one slice ('hito-kire' which also means to kill someone) of takuan was served the samurai would become angry and said, 'Are you trying to tell me to kill someone,' and, if three slices ('mi-kire' which also means to cut oneself or to commit harakiri) of takuan was served the samurai would also become angry and said, 'Are you trying to tell me to commit harakiri?'
It is said that the custom to serve two slices of takuan evolved from these incidents. There is an argument, however, that the foregoing reason only applied to the areas in and around Edo where the Military Government was established. In the Kansai region, serving three slices of takuan is for good luck (Sanpo or three directions and the number 3 is considered auspicious) whereby some donburi ('rice bowl dish' consisting of fish, meat, vegetables, or other ingredients simmered together and served over rice) restaurants in Kansai serve three slices of takuan on purpose.
There is takuan-zuke in South Korea. It was brought in to South Korea during the period under Japanese rule and is referred to as 'takan,' which is the Japanese 'takuan' modified to the Korean-style pronunciation or 'tanmuji,' equivalent of 'takan,' which is a proper noun that has been coined. Tan,' 'mu' and 'ji' mean 'sweet,' 'daikon radish' and 'pickle,' respectively. It tastes very similar albeit on the sweet-and-sour side. There is a pickle peculiar to Korea called chanji ('chan' means salty) which tastes very salty as its name implies. Additionally, not only Japanese restaurants but also some of the Western-food restaurants in South Korea serve takuan-zuke which is a phenomenon that has been established as the Western food was brought over from Japan.