SATI Beyond The Bunch 3rd Quarter 2025

Cartons

cardboard made from primary fibres is stronger than cardboard made from recycled fibres. Cartons must be vented to allow air circulation, but vents reduce strength. In a review by Drs Matia Muka ma, Alemayehu Tsige, and Linus Opara, the authors cite research finding that vent and hand holes can reduce carton compression strength by 20%–50%. They also cite work by Dr Tobi Fadiji and co-authors, who reported that a 2%–7% increase in carton venti lation leads to an 8%–12% decrease in the buckling load. Vents reduce carton strength more when closer to the vertical corners of the carton. Cooling is affected by the total vent area, and the shape, size, and position of vents. During precooling, airflow is predominantly horizontal, but during ship ping, it’s vertical. Airflow is also faster during precool ing than shipping. Moelich and Leuvennink measured the performance of different cartons in simulated pallet stacks. They found that deeper (127 mm) 9-kg grape cartons cooled about 30% faster than shallower (118 mm) car tons. However, deeper cartons increase the cost of packaging material and reduce the number of car tons per pallet stack, which increases shipping costs. The authors also reported that integrated airflow channels in the base of 4.5- and 9.0-kg cartons re duced cooling time by up to 44%. The advantage of the channels is that carton size and numbers per pallet stack are not altered.

SATI

Carton design is a compromise between strength, ventilation, and cost. Weak cartons increase the risk of deformation, collapse, and fruit damage. Poorly ventilated cartons impede cooling, both before and during shipping. No one reading this needs to be told why cost matters. The discussion below focuses on corrugated card board, as this is by far the most common material used for table-grape cartons. Corrugated cardboard is strong, lightweight, print able, and cost-effective. However, corrugated car tons lose strength over time when under load, espe cially when exposed to high humidity. A review by Drs Pankaj Pathare and Linus Opara cites research showing that a load-bearing box can lose 35% of its original strength in 10 days and 45% in 100 days. The strength of cartons depends on the cardboard thickness and material. As Klaus Thieltges explains in an article in Volume 1:1 of the SATI Technical Bulletin,

DEWALD KIRSTEN | LUCENTLANDS

All the packaging elements interact to determine the cooling rate of the pallet stack.

Pallet stacks Carton design interacts with the stacking patterns on pal lets and in containers, which influence how much fruit fits in a container and, therefore, the shipping cost. Stacking patterns also modify airflow, the efficiency and uniformity of cooling, and energy use. As pallet footprints are standardised, the relationship be tween the carton and the pallet dimensions determines

the possible stacking configurations. Different stacking configurations affect the alignment of carton vents and, therefore, airflow. A larger number of smaller cartons in a stack will also have a higher carton surface area per unit of fruit, re sulting in less efficient use of space and more barriers to airflow.

BEYOND THE BUNCH • 10 • QUARTER 3 • 2025