Tracking down contaminated food has historically been a messy affair, sometimes taking retailers and food companies weeks to learn exactly what products they need to pull from store shelves. “Imagine if we could pinpoint with certainty within minutes, not days,” mused Frank Yiannas, one of Walmart’s top food safety executives, in a recent video published by the retailer. Thanks to technology originally designed to monitor cryptocurrency, Yiannas’ vision is closer to becoming a...