Bioluminescence is the production of light by living organisms. The luciferase genes responsible for the generation of light (lux genes) can be cloned from a bioluminescent microorganism into one that is not naturally bioluminescent. Light output can be monitored in real-time and will provide information on the metabolic state, location and quantity of cells in a given environment. Herein we review the applications of Lux-tagged microorganisms in the food industry including their uses in the development of novel food products and processes, for problem solving and for determining parameters important for the control of food quality and safety.