Grocery giants including Walmart and Sam’s Club are beginning to require their lettuce suppliers to hop on the blockchain bandwagon. The companies who provide lettuce and other leafy green vegetables to grocery chains will now need to upload data regarding their foods to blockchain within one year, the companies stated in letters provided to suppliers on Monday.

Both companies highlighted the importance on an E. coli outbreak in romaine lettuce that affected more than 200 people recently, as well as salmonella in products such as eggs and breakfast cereal. By using blockchain to record data, theoretically a supplier would then be able to recognize which farms are infected and quickly put an end to the supply for restaurants and consumers.

“Walmart believes the current one-step up and one-step back model of food traceability is outdated for the 21st Century and that by, working together, we can do better,” Walmart said in its letter. “There is no question that there is a strong public-health and business-case for enhanced food traceability.”

Although Walmart was able to determine the affected area and get the contaminated food out of its grocery stores, it said millions of heads of romaine lettuce was required to be removed from the marketplace, and consumers lost their confidence in the lettuce regardless of the region it was grown in. By enabling blockchain, all fresh lettuce suppliers are expected to be able to trace their products back to farms “in seconds – not days,” Walmart said in a letter to suppliers. CNBC also noted that direct suppliers will be required to conform to Walmart’s standards are “enable end-to-end traceability” back to farms by Sept. 30, 2019, the company stated.

Walmart continued piloting the technology on IBM’s Food Trust blockchain for nearly 18 months, using it to track products from mangoes to chicken. In result, the time it takes to track a food from a Walmart store back to the source decreased significantly to only a few minutes, compared to the days or sometimes weeks it would typically take, according to Walmart.

Walmart did not note how much the blockchain move would cost farmers, however, IBM launched a site to walk suppliers through onboarding and aims to implement a  “user-friendly, low-cost” transition.