A sensor is defined as a single device that is founded on chemical and physical principles including electrochemistry, fluorescence, thermal, surface plasmon resonance, piezo, reflectometry, chemo and bioluminescence, and optics. More specifically, the term chemical sensor refers or describes a small appliance that is capable to deliver instantaneous information about the chemicals (e.g. concentration, identification) and other compounds present in either the food sample or food system. These sensors can be deployed throughout the different steps during the manufacturing, storage, and transport of foods. This chapter offers the readers with a summary of some of the sensors applied by the food industry to measure and monitor issues related with food contamination and spoilage, with emphasis in the application of electrochemical sensors.