I knew Mom wanted us to have dinner with the family, so when my stomach started growling on the four-hour drive to her house I dutifully chose a strawberry milk at the truck stop over the fried chicken I knew was at the counter.

My husband and I both got a bottle of pink moo juice (which is markedly different from yellow cow water) and one was past its “Use by” date.

When I walked back in to tell the cashier, she simply said, “Ew,” and held out her hand for the offending product while I went to get a new one.

I knew the date on the bottle told me when my drink would taste the best; it didn’t really say much about whether it was safe.

Safety is a result of a product’s history.

Brett Lucht and William Euler — chemistry professors at the University of Rhode Island – came up with a nearly invisible dye that will turn red when a package of food gets above 40 F.

That could tell me whether a bottle of milk was likely to be safe before I bought it.

The professors also have a patent for a two-bar code system that uses one made with color-changing dye to mask the one that’s typically scanned at the checkout when the product has warmed up too much.

Sounds pretty cool. I wonder which manufacturers would be willing to use it?