Settings during refrigerated transport of fruit, expert – course participant conversation

Published on
July 1, 2022

Do you have questions about refrigerated transport? In the below conversation expert Leo Lukasse, Wageningen University & Research answers the question from a participant of the Refrigerated Transport Technology course.

โ€œ๐˜‹๐˜ฆ๐˜ข๐˜ณ Leo Lukasse, ๐˜ ๐˜ซ๐˜ฐ๐˜ช๐˜ฏ๐˜ฆ๐˜ฅ ๐˜ต๐˜ฉ๐˜ฆ ๐˜ค๐˜ฐ๐˜ถ๐˜ณ๐˜ด๐˜ฆ ๐˜ฐ๐˜ฏ ๐˜ณ๐˜ฆ๐˜ง๐˜ณ๐˜ช๐˜จ๐˜ฆ๐˜ณ๐˜ข๐˜ต๐˜ฆ๐˜ฅ ๐˜ต๐˜ณ๐˜ข๐˜ฏ๐˜ด๐˜ฑ๐˜ฐ๐˜ณ๐˜ต. ๐˜ ๐˜ธ๐˜ข๐˜ด ๐˜ธ๐˜ฐ๐˜ฏ๐˜ฅ๐˜ฆ๐˜ณ๐˜ช๐˜ฏ๐˜จ ๐˜ช๐˜ง ๐˜ ๐˜ค๐˜ฐ๐˜ถ๐˜ญ๐˜ฅ ๐˜ข๐˜ด๐˜ฌ ๐˜บ๐˜ฐ๐˜ถ ๐˜ง๐˜ฐ๐˜ณ ๐˜ด๐˜ฐ๐˜ฎ๐˜ฆ ๐˜ข๐˜ฅ๐˜ท๐˜ช๐˜ค๐˜ฆ, ๐˜ด๐˜ช๐˜ฏ๐˜ค๐˜ฆ ๐˜บ๐˜ฐ๐˜ถ๐˜ณ ๐˜ฆ๐˜น๐˜ฑ๐˜ฆ๐˜ณ๐˜ต๐˜ช๐˜ด๐˜ฆ ๐˜ง๐˜ข๐˜ณ ๐˜ด๐˜ถ๐˜ณ๐˜ฑ๐˜ข๐˜ด๐˜ด๐˜ฆ๐˜ด ๐˜ฎ๐˜บ ๐˜ฐ๐˜ธ๐˜ฏ,โ€ starts Georg Tsvetanski, Packhouse Manager at Fruktalina, his mail to professor Lukasse.

Georg: โ€œWhat conditions need to occur for condensation to form on the fruit? What is the correct procedure for loading a refrigerated truck, if I am to deliver apples at 4-6C? How does the refrigeration unit in the truck react when I load fruit that is of higher temp than the surrounding temp inside the truck? If I need to deliver fruit at 4-6C, what needs to be the temp of the fruit at loading, and what parameters do I set for the refrigeration unit in the truck? If my refrigerated corridor which leads from the cold store to the truck is at 8C is this a problem?โ€

Leo: โ€œThanks for your inquiry. Let me give it a try. Though this is one of those moments where I feel that it is too easy to preach simple theories from behind my desk. To transport apples at 1-2C, I would set trailer refrigeration unit at continuous run and supply air temperature control. Return air temperature control is possible, but then make sure to use sufficiently tight top freezing protection settings, if available. Of course itโ€™s nice if apples are properly precooled, but if thatโ€™s not the case their temperature will slowly converge to the setpoint or just above it.

Frost exists of white needles. Frozen condense is ice (glassy). How can frost (not ice, but frost!) form on apples? First reduce the apple temperature below 0C, and then bring it in touch with air which has a dewpoint warmer than the appleโ€™s surface temperature. What is โ€˜air which has a dewpoint warmer than the appleโ€™s surface temperatureโ€™? Well, itโ€™s air warmer than the apple, while the air is not exceptionally dry. I hope this helps a little in solving your puzzle.โ€

More information? Interested in the topic? Reach out to expert Leo Lukasse, Wageningen Food and Biobased Research or visit the (online) course Refrigerated Transport Technology webpage.