Taking the temperature

Produce Grower magazine recently spoke with Dr. Jeffrey Brecht, a University of Florida professor who specializes in postharvest physiology. Brecht worked with a team of six researchers, and two grad students, studying innovations for tracking the freshness of produce throughout the shipping process. Made possible by a grant from the Walmart Foundation, Brecht’s team determined that a first-expired, first-out model would benefit the company. He presented his findings at the International Horticulture Congress in Brisbane, Australia.
 

Produce Grower: Your research was made possible by a grant from the Walmart Foundation. What interested you and your team in the project?

Jeffrey Brecht: The research is an area that the people on our team have been working on for almost ten years in one way or another. It was just a happy circumstance that the Walmart Foundation decided to fund a grant program in strawberry sustainability. The program was managed through the University of Arkansas, so that’s where the funding for the research came from.
 

PG: Was your program solely focused on strawberries then?

JB: We actually worked with a lot of other fruits, beside strawberries. But this research program was specifically designed around strawberries.
 

PG: And can you describe what your research was and how you conducted it?

JB: We used off the shelf wireless temperature sensors to map the temperature within trailer loads of strawberries. Then, what we did that’s unique to our group, we used that temperature history, along with a shelf life model devised by two of the team members. One team member collected the data on how temperature affects the quality changes and another wrote the actual model.

So the idea was that if you know the temperature history of the strawberries from the moment they’re harvested, to the pre-cooling, onto the trailers and to the distribution center then you can predict how much remaining shelf life the strawberries have. We were able to do that because of the temperature probes distributed throughout the trailer on a propellant basis.
 

PG: Can temperature within a trailer vary in damaging ways?

JB: There’s actually the potential for fairly significant temperature differences within the trailer, enough that it could have an effect on shelf life.
 

PG: How does knowing the temperature history help growers or distributors?

JB: You can use that information, to predict the remaining shelf life and distinguish between different loads, and different pallets within loads, that have more, or less, remaining shelf life and use that to more intelligently manage the distribution from the distribution centers to the stores.

What we’ve found is that Walmart distribution centers can be distributing to 100 or 200 different stores and they can be right next to the center or over 200 miles away. That’s a pretty big difference. So that was the whole point of our research. If we used a first-expired, first-out model rather than first-in, first-out (which is what everybody uses) it would change the way they distribute strawberries and the average quality across all the stores that any distribution center services would be better; versus if you send everything first-in, first-out chance is going to determine who receives the strawberries with the best shelf-life. So you might, by chance, choose the lot that has the least remaining shelf life and send it to the farthest away store, or hold it back in the DC an extra day while you ship other things out. You can see how that would have negative effects. So, the whole idea was to manage things more efficiently and more intelligently. Therefore, if the quality is uniformly better then it stands to reason that the customers would be more consistently happy.
 

PG: You mentioned the first-in, first-out model. What is that?

JB: The model that is used universally (by distribution centers), to my knowledge, is this: whatever product arrives first goes out to stores first. Whatever comes in second, goes out second. That is the standard by which most people work. But it doesn’t take into account the condition of all the produce coming in. We were looking at the shelf-life model to allow a first-expired, first-out, meaning: the produce with the shortest remaining shelf-life should go out first and anything with a longer shelf-life, if possible, should go out later.
 

PG: And to institute a first-in, first-expired model what would growers and distributors need to do?

JB: If they added a couple of temperature recorders then they could use that information to start managing distribution differently.

One of the students from our team looked at temperature mapping in shipments to determine where the best locations for temperature trackers would be to get a picture of the temperature throughout the whole load. He found that the best locations were: front, middle and back. If you have those temperature sensors you get a good picture of the temperature within the whole load. We used two temperature measurements per pallet, which would be 40 measurements. But we were trying to get a finer look at temp differences.
 

PG: And this research is applicably specifically for strawberries?

JB: No, it can be applied to anything. It was strawberries for this test because that was what the grant program was specifically for and strawberries were what we had done this work on previously. The model was already developed.