"What happens is everybody's guilty until proven innocent, all of this product comes off of the shelf, everybody is incriminated," he said. "Generally when the dust settles you find out that it was one supplier, maybe one production line - so if you had the ability to identify this quickly you could target and remove the product quickly and protect people from getting ill."
The traceability data points that Walmart and IBM identified include the farm location, or lot number, or the date of a harvest. But what the company calls transparency attributes are different: including whether the food is sustainably grown, whether it is born organically, or if pesticides were used in the production of the food. Walmart wants to combine all of these points for the full picture.
"We think if we do that for the entire food system there would be intelligence gained, when you see the long view, that will optimise the food system," Yiannis said. "So we have no doubt that could lead to a better flow of food from farm to fork - for every day of shelf life you take out of the flow of food, that's a day of shelf life you give back to the customer.
"As soon as you've picked that strawberry it starts dying, and your goal is to get that strawberry from the farm to the customer as soon as possible - so the more efficient you can do that the better."
Ultimately Walmart expects consumers could interact with labels on their food, perhaps using a smartphone app, to bring up the journey of the product and any other information that they want to see. For this to work, of course, would require the active participation of many other big players in the food industry.
"Our view is for a solution like this there is the need to collaborate," Yiannis said. "This food system of ours is a pretty complex food system, there are a lot of actors and players in it, so we envision a blockchain solution for food transparency to be collaborative, and we want as many people in food production to be involved and engaged in that."
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