Biosensors are biomolecular probes measuring parameters in biological systems: a biochemical interaction at the probe surface becomes a quantifiable physical signal. Immobilising enzymes, antibodies, receptors, DNA, cells or organelles on a transducer forms the basis of various biosensors, which the food industry uses widely: measuring components in foods and beverages, detecting contamination and adulteration, and monitoring and controlling fermentations, bioconversions and biotransformations. From glucose sensors guiding fermentation to rapid pathogen and allergen tests, biosensors deliver fast, often portable answers where laboratory turnaround is too slow.