Investigating the effect of cold store airlocks on the temperature control and protocol compliance during orange handling operations

Abstract

Background: Cold storage facilities must balance energy conservation with temperature compliance for perishable exports, yet comparative evidence on airlock design and refrigeration technology remains limited.
Objectives: This study compared cooling performance of two cold storage facilities with differing refrigeration technologies and airlock configurations during orange handling.
Method: iButtons^® were placed in orange cartons across five pallets per facility during July–August, coinciding with peak Western Cape Valencia orange export season. CS1 used conventional refrigeration with non-temperature-controlled (NTC) airlocks; CS2 used advanced refrigeration with temperature-controlled (TC) airlocks. Data were recorded at 15-minute intervals and analysed using descriptive statistics, a chi-square test, and the Mann–Whitney U test. Cooling rate was defined as time elapsed until average pallet temperature first reached 5 °C.
Results: CS2 achieved superior control, with 85.92% of readings at or below 5 °C versus 57.46% for CS1. Mean temperatures were 2.98 °C (CS2) and 6.14 °C (CS1). CS2 reached 5 °C within approximately 1.5 hours of pallet arrival; CS1 required approximately 25 hours. Differences between facilities were highly significant (p < 0.001), with large effect sizes (Cohen’s d = 1.04; rank-biserial r = 0.73).
Conclusion: TC airlock systems substantially improved protocol compliance over selective-cooling approaches. For citrus exports requiring sub-5 °C storage, TC airlocks are essential for maintaining export quality.
Contribution: Findings offer evidence-based guidance for cold chain operators and policymakers balancing energy efficiency with temperature control in South African agricultural export management.