Tosa Vinegar Tosazu Dressing Technique
Kochi (Tosa) Prefecture — named for the katsuobushi capital of Japan
Tosazu (土佐酢) is a refined Japanese vinegar dressing made by simmering katsuobushi (bonito flakes) in rice vinegar with mirin and soy sauce, then straining. Named after Tosa (Kochi Prefecture), historically famous for its katsuobushi production. Tosazu combines the brightness of rice vinegar with the deep umami of katsuobushi, creating a more complex, rounded acid dressing than plain sanbaizu. Used for sunomono, as a marinade for thin-sliced white fish (Tosa-style), and as a dipping sauce for cold tofu. The tosa technique of applying lightly to white fish then serving after brief marination is called 'Tosa-ae' and is a distinctive Kochi preparation.