I am a mechanical engineer by training (degree in Engineering Science, many years ago). I am also an academically trained historian and anthropologist, and nowadays, I do engineering-oriented public policy analysis. My chemical knowledge approximately ends with NAPOM (Nature and Properties of Materials, ie. Introductory Metalurgy). The little I know about organic chemistry is confined to fuels, and the kindred topics of batteries and explosives. What follows is a speculation which arose in the course of buying groceries from Amazon. I became aware that Amazon was inadvertently testing the limits of quality control, and started thinking about what would be required to keep them honest. One obvious requirement is that frozen foods should proveably stay frozen.
The object is to create a product tag for frozen goods, specifically frozen foods, which reveals whether they have remained frozen, or not.
An uninformed suggestion runs as follows: Two chemicals are held apart, in separate frozen layers, sealed up in a plastic package. If the package thaws, the chemicals combine, and go through an irreversible reaction, which produces a change of color, litmus paper fashion. Certain conditions are that the thing would have to be very cheap, on the order of a fraction of a cent, and that it would have to be reasonably nontoxic.
This would be applied to a packet of noodles, costing a dollar or two. So one could not use a micro-controller-based sensor, or anything like that.
I place any conceivable rights I might have in the foregoing into the public domain, and I invite your critique, suggestions, ridicule, etc.
Andrew D. Todd
1249 Pineview Dr., Apt. 1
Morgantown WV 26505