Proben or proven is a type of street food popular in some regions of the Philippines. It is made from the proventriculus of a chicken, which is an organ part of the digestive system of chickens. The proventriculus is marinated in salt, vinegar, and other spices, then coated in wet batter and tossed in dry flour just before frying. It is served either in a small bagful of vinegar or skewered on bamboo sticks to be dipped in the vinegar just before it is eaten. A nutritional study conducted by the University of the Philippines Los Baños (UPLB) noted that, as with most street foods, the microbial quality of the proben is a concern. However, the study noted that the pathogenic food-borne microbes in proben are mostly destroyed when it is cooked. The microbes only return if the proben is stored at ambient temperature after having been cooked.