Properly cooked garbage is a widely accepted, economical, and good source of nutrition for hogs. However, incompletely cooked or raw garbage represents a real hazard as a source of contagious diseases among livestock. The simple, rapid, and reliable field test described in this paper can be used to determine whether swill has been cooked enough to destroy disease agents such as hog cholera virus. The test monitors the effect of cooking upon the survival of the common enzyme, acid phosphomonoesterase. Garbage exudate is incubated with the substrate phenolphthalein monophosphate. If present, the heat-labile enzyme reacts with the substrate to form phenolphthalein. The latter produces a red color at alkaline pH, indicating insufficient cooking of the hog swill. The test may be performed in the field at the cook-site, and a valid index of proper cooking can be obtained without the presence of a livestock inspector during cooking.