Every sushi chef has a secret recipe for the sushi rice vinegar, and it is hard to describe in detail of all the different variations that may exist. However, the basic ingredients are the same.
Kombu is first washed lightly and placed in a pot with rice vinegar. It is then put to a simmer and immediately discarded. It only takes a few seconds of boiling water to extract a mild aroma of kombu. Next, the sake, salt, and sugar are added and again simmered until the alcohol from the rice wine is reduced. This mixture is then refrigerated before use.
All chefs use different variations, and amounts of ingredients. Some even refrigerate the sushi rice vinegar for days until they think all the flavors are settled. The color of the sushi rice is usually white, but it can become pink if a chef prefers a particular red vinegar, or brown if they use aged black rice vinegar. Some try not to use heating as much as possible, for they fear that some of the flavors can be lost. Regardless of the variations of methods, or ingredients they use, they always keep in mind that the purpose of the sushi rice vinegar is to enhance the flavor of the main ingredient, raw fish.