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On May 6, 2014, as I read through the morning’s incoming email, a Food Safety Alert from the US Food and Drug Administration (FDA) announcing a “voluntary recall of mangos due to possible health risk” from the bacteria Listeria caught my eye. This grabbed my attention because at the time, a handsome sunset-hued mango, purchased several days before at my neighborhood market in Portland, Oregon, was ripening on the kitchen counter.

The FDA notice explained that the recall covered mangos “shipped to retailers and distributors in limited quantities within five (5) US states (Arizona, California, Colorado, New Jersey and Texas).” It included a link to photos of PLU stickers for the mangos covered by the recall. One of the two matched the PLU sticker on my mango.

I wondered: Was it possible that some of the mangos shipped to California had ended up in Oregon?

As I learned, the answer is complicated. It turns out that tracing produce from kitchen counter back to its grower involves information that is far more difficult to obtain than one might guess, as key details are often considered confidential business information.

What’s more, each type of produce may travel a different route from field to store. Still, what I learned applies to most whole fruits and vegetables you might buy. So let my mango be your guide.

What does a PLU code reveal?

You’ve probably seen the stickers bearing numbers affixed to most smooth-skinned produce sold without packaging. PLU stands for Price Look-Up code, a voluntary system that was designed in 1990 to make checkout pricing and inventory control easier. The PLU codes most noticeable at home in the kitchen are those on labels attached directly to produce. Others appear on store shelf cards, on tags such as the twist-ties holding a bunch of kale or on other packaging.

The code’s basic four digits simply signify a produce variety and size category. A “9” preceding the four-number string indicates the produce is organically grown and an “8,” that the produce is genetically modified.