What is the mixture of rice vinegar, sugar, and salt used to season sushi rice called? It is called sushi-zu.
Sushi-zu is the seasoned vinegar dressing mixed into cooked rice to make sushi rice, or sushi-meshi. Its basic ingredients are rice vinegar, sugar, and salt. The proportions vary by chef and region: some preparations are sweeter, while others emphasize salt or acidity. Kombu or sake may also be added for extra flavor, but they are not essential to the basic mixture.
The dressing gives sushi rice its characteristic balance of sourness, sweetness, and savory seasoning. It also helps distinguish sushi rice from plain steamed Japanese rice. The cooked rice is traditionally mixed with the dressing in a shallow wooden tub called a hangiri, then cooled so it becomes glossy and suitably firm without turning mushy.
Sushi-zu is not the same as soy sauce, ponzu, or mirin. Soy sauce is a dipping condiment, ponzu is a citrus-seasoned sauce, and mirin is a sweet rice wine used in cooking. Sushi-zu is incorporated into the rice itself. It may also be described in English as seasoned rice vinegar or sushi vinegar.