Ponzu is a soy sauce blended with citrus juice. Ponzu is made by simmering mirin, rice vinegar, katsuobushi flakes (from tuna), and seaweed (kombu) over medium heat. The liquid is then cooled, strained to remove the katsuobushi flakes, and finally the juice of one or more of the following citrus fruits is added: yuzu, sudachi, daidai, kabosu, or lemon. They are first peeled then juiced so that the bitter flavors from the skin will not interfere with the final product.
The word ponzu was derived from the the Duch word pons or citrus orchard. Therefore pons became pon su (“pon”vinegar)and then ponsu. The Netherlands was one of the few countries that Japan has traded with during the Edo period, and this theory is widely accepted.
There are other theories that explain that the word ponzu may have come from the Hindi word for the number five,or panch. Panch later became a term for mixed drinks with five ingredients and used in the English language as punch. Ponzu sometimes includes small amounts of rice vinegar, or sugar and can up to 5 ingredients. The word panch may have been borrowed to name pan su (“pan” vinegar), then panzu and finally ponzu. However, this theory is less accepted.
Ponzu is used for light tasting fishes to give them more accent with the citrus, or to freshen up fish that may have a slight scent that can hinder the sweet aromas.
Ponzu shoyu is traditionally used as a dressing for tataki (lightly grilled, then chopped meat or fish), and also as a dip for nabemono (one pot dishes) such as shabu-shabu. It is used as a dip for sashimi. In the Kansai region, it is offered as a topping for takoyaki.