Vinegar began to be added to the preparation of narezushi in the Muromachi period (1336–1573) for the sake of enhancing both taste and preservation. In addition to increasing the sourness of the rice, the vinegar significantly increased the dish's longevity, causing the fermentation process to be shortened and eventually abandoned. The primitive sushi would be further developed in Osaka, where over several centuries it became "oshi-zushi" or "hako-zushi"; in this preparation, the seafood and rice were pressed into shape with wooden (typically bamboo) molds.