Fresh Test Sensors - The idea

It should be possible to create extremely cheap sensors that tell if a product went above a given temperature. For example, there could be a chemical sticker that changes state (and color) when it goes above a given temperature, something similar to thermochromism, except the change would need to be irreversible.

Chemical Sensors

This would require developing a cheap non-toxic material that makes an irreversible state change when it goes above some temperature T. The chemical would be put into a sticker on goods like milk cartons, egg containers, and other refrigerated products.  The simplicity of a chemical change also, however, comes with a lack of detail. The change only tells you that it exceeded a temperature, not how long the temperature was exceeded, which may be an important factor.

Electrical Sensors

The alternative is to make cheap chips that have temperature sensors and a tiny battery. The chip would spend 99% of it’s life sleeping conserving battery live. For a second every hour, it would turn itself back on and measure the temperature. The hourly temperature would be recorded until the good arrives at the final point of sale (the grocery store). There a grocery worker would use and RFID scanner to scan the package and see a summary of the temperature history of the good. If it doesn’t fit the federal, state, and store policy, then the good is rejected. Also worth noting is that other sensors could also be used to measure exposure to sunlight and acceleration.

If implemented at scale, these sensors could ensure food safety is cheap and simple. This could also apply to imported and exported goods.