Sushi started out as a fast food business in the streets of Edo (old name for Tokyo) a little less than 200 years ago. These Edo style sushi were prepared and sold on stands when there were no refrigerators available and for this reason many adaptations were made so they will not spoil too quickly. The most important characteristic is the sushi rice which uses vinegar, and the use of wasabi as a condiment. But these modifications were not made unless they had more than one benefit. Sushi rice used to be stronger in the old days for it required more vinegar to prevent spoilage, but it matched the taste of raw fish for the vinegar helped make it taste fresher. Wasabi’s culinary purpose is to bring out the flavors of the ingredients (raw fish), but it has strong anti bacterial properties which helped prevent food poisoning. Many ingredients were cured, or immersed in soy sauce to the increase the shelf life, and it is not until after the refrigerator was invented, when many varieties of raw ingredients became available any time of the year regardless of the location.