Tapai is a dish served mostly in East and Southeast Asia and the Philippines. It consists of a starch such as rice that has been fermented for days until it develops a sweet flavor and the sugars have been converted into alcohol. Sweet tapai is considered a treat or dessert in many regions and can be complemented with other sweet foods such as coconut or dried fruits. Although the dish is usually made from glutinous rice, it also can be made by fermenting regular rice, cassava root, plantains or sweet potatoes. When completed, the tapai is traditionally wrapped in banana leaves for storage or sale at a market.
One aspect of the preparation of tapai that gives it a unique character is the fermentation process. By using a collection of bacteria, yeast and molds, the starches in the food are converted into other forms, such as sugar and alcohol. This is most often done by using a product known as ragi. Ragi is a chunk of dried, uncooked rice that has been powdered and mixed with water and various other ingredients so it can support yeast and bacteria, creating a dry, solid starter. The ragi is used by crushing it into the food to be fermented, transferring all of the starter cultures that are held within it.
The types of foods used to make tapai usually have a high amount of starches. This is because the starch is what the cultures use as food and what is converted to provide flavor. The chosen food, whether it be rice, potatoes or cassava root, is first cooked until it is soft and the natural elements inside have developed. After the food has cooled to room temperature, the ragi is added and the entire mixture is placed in a container, where it is allowed to ferment for three days or more.
As the tapai ferments, sugars develop to make it sweeter and it also begins to excrete a liquid that gathers at the bottom of the container. The liquid is actually an alcoholic rice wine and the amount produced is directly related to the amount of starch in the food that is fermenting. The longer the fermentation is allowed to progress, the more alcoholic the tapai will become. There is a point during fermentation when the character of the food will change and cause the sweet taste to turn into a sour taste as certain acids begin to dominate the mixture. Although some people find this desirable, others feel it means the tapai has spoiled.