SATI Beyond The Bunch 3rd Quarter 2025

Delele and co-authors investigated airflow within and around a stack of grape-filled cartons. They reported that only some cooling air penetrated the stack, resulting in appreciably slower cooling of cartons in the centre. Their results align with other research, which shows that cooling efficiency decreases with increasing stack size. Leuvennink and Moelich measured cooling profiles in a forty-pallet commercial cooling tunnel. They saw signifi cant increases in cooling time the further pallets were away from the cooling coil, and on the inside compared with the outside of the pallet stack. They also observed rapid cooling of grapes in 36 x 4 mm liners inside 4.5-kg cartons located on the delivery-air side

of the pallet. In some cases, berry temperatures dropped below zero within 3–5 hours of forced-air cooling. At the time, the 36 x 4 mm liners were a recent introduction. Leuvennink and Moelich ‘s results confirmed the uneven cooling of fruit in pallet stacks, a phenomenon known to cold-storage operators but previously unquantified in the 36 x 4 mm liners. The authors recommended that pallets of different packaging types shouldn’t be mixed in cooling tunnels, as this leads to different cooling rates and increased risk of chilling injury and freezing when very low set points are used. Lower set points were commonly used with unperforated liners.

Packaging design tools

Initially, Tsige will work with real packaging to obtain the necessary data for constructing a mathematical model. He will study each packaging component separately before combining them in the model. Once he has a model, he will validate it by compar ing its predictions to airflow and cooling in the real world. The model can then be used as a tool to test and improve packaging.

Until recently, packaging evolved by trial and error. Thanks to computing advances, researchers can now model the performance of different packaging con figurations, enabling them to test multiple iterations virtually before undertaking the trouble and expense of real-life trials. The review by Mukama and co-authors lists numerous recent studies that apply computational fluid dynam ics to packaging and cooling systems for fruit. Much of this work has been done at Stellenbosch University.

This year sees the start of an NRF-fund ed project on table-grape packag ing led by Dr Alemayehu Tsige, senior researcher in the Packaging and Cold Chain Research Group in the Department of Horticultural Science at Stellenbosch University. Tsige aims to help the industry solve problems related to non-uniform air flow and temperature distribution during table-grape export. He will also investigate SO 2 dynamics during different handling stages. The other aspect of the project is how pack aging impacts space utilisation and energy efficiency.

ADOBE STOCK

Acknowledgements The following specialists provided technical inputs. • Dr Johan Fourie. ExperiCo Agri-Research Solutions. • Dawie Moelich. SATI. • Dr Alex Tsige. Department of Horticultural Science. Stellenbosch University.

BEYOND THE BUNCH • 11 • QUARTER 3 • 2025