Patent ID: 7014816

Claim:
An indicator device, comprising: a substrate; a first polymeric matrix coated on the substrate; a second polymeric matrix covering all of the first polymeric matrix except for an edge of the first polymeric matrix, the second polymeric matrix impermeable to volatile bases generated by decomposing food; and an indicator compound disposed within the first polymeric matrix, the indicator compound being colorimetrically responsive at temperatures below 0° C. to the volatile bases generated by food decomposition; wherein the first polymeric matrix is formed by an acid catalyzed polymerization of a monomer material comprising a tetraalkoxysilane, an alkyl trialkoxysilane, or a mixture thereof; wherein a distance of colorimetric response of the indicator compound disposed within the first polymeric matrix increases with increased exposure to the volatile bases, wherein food quality can be determined by measuring the distance of colorimetric response over a predetermined time period at a particular temperature.