Fresh produce is the albatross around grocers' necks — it's got a razor-thin profit margin, it spoils quickly, and illnesses can prompt public hysteria. But now, they hope blockchain is a solution.

What's going on: IBM is using blockchain to track the journey of a bunch of spinach from the farmer to the shopper's cart. Knowing, and trusting, the vegetable's precise origin will reduce cases of people getting sick from food, IBM says.

How it works: In a blockchain, a network of computers creates a record of any string of events. That allows it to track anything from transactions to food. No middleman is involved, which blockchain enthusiasts say increases trust between parties.

For example, if a single bag of spinach infects someone with E. Coli., shoppers will stay away from any and all leafy greens for weeks, even months, until they're confident they won't get sick.

Using blockchain to track that bag means determining exactly where the contaminated spinach came from, instead of sending the entire industry into a whodunnit panic, says Brigid McDermott, who leads IBM's blockchain food-tracking arm.

Food is also perishable — another big headache for retailers. Blockchain may one day solve that too, McDermott says.