Riau has a variety of typical dishes, one of which is the SAMBAL TONGAK ASAM or Sambal Terong Asam. The cuisine is usually served with grilled shrimp, and the main ingredient is sour eggplant (Solaum ferox Linn) which can be made into a sauce in a fresh state or grilled first. Sambal Terong Asam is the typical dish of Riau which is always the "accessories" dish for the Malays in Riau, especially the Malay Archipelago and the Malay East coast of Sumatra.

This cuisine is also found in Borneo with the same ingredients that is sour eggplant in the Dayak Ngaju language called Rimbang. But for the ingredients used in the sour eggplant sauce, it is of a kind that is small or small fruiting - which has a sharper taste and aroma. Generally served with smoked fish.

Sour eggplant growing place of origin is unknown, there are planted ones and there some also growing in the wild. It is spread from India to the territory of Papua New Guinea, including all countries around Southeast Asia.
Eggplant fruit acid contains water, carbohydrates, protein, fat, fiber, minerals and vitamins. Sour eggplant is usually does not get diseased or serious pests.