Sudachi is a citrus local to the Tokushima prefecture Shikoku region which is located in southern central Japan.
They are the smallest citrus (about the size of a golf ball) used in Japanese cuisine and often used to season grilled fish (especially Pacific Saury which are in season at the same period) right after they are cooked.
They are expensive outside this region since they are not grown anywhere else.
Local medical research has found out that Sudachi prevents spikes in blood sugar level and are beneficial to patients with diabetes.
It begin to grow during the autumn and harvested before they become ripe since the peels are strongest in aroma during this stage.
The peels are grated and used as a condiment, but it is only local to the Shikoku area and not widely used throughout Japan.
Its juice is added to soy sauce and used to dip ingredients from a steamboat dish (hot pot). The juice is also blended with other citrus juices to make ponzu.
Since sudachi are used in the unripe stage,the skin are peeled before juicing them to prevent the juice from getting a slight bitter taste.
Sudachi is often mistaken with the yuzu but it is much smaller in size,and the have a smoother skin.