After winnowing the original 1,656 documents down to 264, the team furthered screened them to identify about 32 of the most relevant strategies. They then validated some interventions they identified with four cooperating packinghouse facilities.
Initially they sampled each facility before any interventions and performed a formal root cause analysis with facility personnel.
“What do we think the problem is?” Wiedmann said. “Once we identified it, we looked at potential solutions from the literature but also from a common-sense standpoint. What interventions should we be doing? Then we followed up to see if they had an effect.”
Based on those results, the researchers developed a step-by-step approach packinghouses can use to use to conduct a root cause analysis to identify the most likely factors behind specific persistence as well as appropriate interventions.
Wiedmann said it was “absolutely essential” to have this type of produce-industry participation to ensure their results were applicable to produce facilities.
“To figure out what’s happening in the real world, we need to be in a real facility,” he said.
Interventions they identified but were too difficult to validate experimentally in a packing facility were tested by using a previously developed computer model.
“We’ve re-created produce facilities in almost 3D, so we can identify places where Listeria can survive over time and we can see what happens as we change things,” Wiedmann said.
In the end, the researchers plan to develop a decision-support tool the industry can use to develop intervention strategies. Much like they did when they were validating interventions, the researchers will seek industry input on the support tool from a focus group.
The tool also will allow plant personnel to run “what if” scenarios to compare different strategies, but it won’t replace the human element.
“The operator will still make the decisions, but we want to improve the chances they make the right decision,” he said. “The model doesn’t make the decision for them, but it helps them make better decisions more quickly.”