Testing and design of a passive precooling system for the postharvest quality preservation of Alps blueberries from Valtellina

Background Fruit quality must be maintained during transportation to markets to guarantee the acceptability from consumers. A rapid and uniform postharvest cooling is critical to maintain the quality and enhance the shelf life of fresh horticultural products. The aim of this work is to test a passive precooling system on highbush blueberry (Vaccinium corymbosum L.) from Valtellina (SO, Italy) to verify precooling performance on this small fruit. Based on experimental results the precooling trend was modelled and a dedicated system was designed for the optimization of Alps blueberries cold chain. Methods The system was used for the precooling during transportation of the blueberries from the field to the storage cells. The monitoring of the internal conditions was carried out by means of six stand-alone data logger temperature sensors, positioned in different points of the pack. Based on the temperature profile registered during transport, precooling performance was analyzed. The evolution of qualitative characteristics of stored fruits were evaluated by periodic sampling, analyzing the percentage of damaged berries, the weight loss and the texture. Moreover, the main chemical analysis (titratable acidity and content of total soluble solids analysis) were carried out. Results The temperature profiles during transport WPPS shows how this device is not fast enough in tearing down the blueberries field heat. Indeed, after two hours of use, the temperature inside the device has not dropped below 15 °C. It is necessary to design a dedicated system for blueberries with structural features allowing a rapid cooling at least to 5 °C within 2 hours. To reach this objective a computer simulation, using finite elements method modeling, taking into account the thermo-physical properties of materials used and the boundary conditions arising from experimental data collected was carried out. Conclusions Computer modeling provided the characteristics of geometry, thickness, type and density of the material to obtain the desired precooling performance.