We are developing a paper-based cell free system that detects spoiled milk. Relying on the detection of AHL molecules used by bacteria in quorum sensing, our system will be a synthetic gene network freeze-dried on paper. We hypothesize that with a working system when AHL is present the system will produce a red pigment providing a visual cue the milk is spoiled. Because spoiled milk contains bacteria producing AHL, when our system comes into contact with spoiled milk the paper should turn red.