An outbreak of food poisoning last January has raised disturbing questions about the nation's food supply. After eating hamburgers at Jack in the Box restaurants in several Western states, three children died and some 500 people became ill. The culprit was a virulent strain of Escherichiacoli, a bacteria that has been linked to other recent food-poisoning outbreaks. E. coli is one of many toxic organisms that can taint food at various points along the farm-to-table food-supply chain. At the same time, environmental pollution and chemical pesticides and additives pose still other threats to food safety. Experts agree that the current food-inspection system, in place since the early years of this century, is poorly designed to protect consumers.