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Relationship of typical core temperatures after hydrocooling on retention of different quality components in sweet cherry Published In HortTechnology, 24 (4):457-462, 2014, by P.M.A. Toivonen

The research was conducted to first determine the commercial reality in regards to effectiveness of hydrocooling of sweet cherries (Prunus avium) at commercial packing houses. Temperature data obtained from the commercial studies were then used as a guide to evaluate the effect of small differences (0.5, 3, and 5 °C) in sweet cherry core temperature on the quality retention of ‘Sweetheart’ sweet cherries over 6 weeks of storage to simulate container shipment. Sweet cherry core temperatures after in-line hydrocooling and at the time of packing were generally around 3 or 5 °C. Once palletized and placed in commercial cold rooms, the internal boxes of a pallet did not cool any further. Only when a pallet was exposed to direct airflow from cooling coils did the exterior boxes in an assembled pallet show any further reduction in core temperature of packed sweet cherries. Experiments to evaluate the differences in quality retention at close to ideal core temperature (0.5 °C) vs. at more typical 3 or 5 °C core temperatures demonstrated significant decline when the two higher temperatures were maintained over 6 weeks of storage. Sweet cherry firmness, titratable acidity, and stem removal force value declines in storage were significantly affected by these small differences in core temperature, showing the best retention at 0.5 °C. Stem browning increased significantly with 3 or 5 °C storage by 6 weeks of storage. Decay was also significantly increased with warmer temperatures, but the results were variable likely due to differences in fruit infection at the time of harvest. Soluble solids were unaffected by storage temperature, and weight loss and pitting severity were somewhat affected. These results support the need for post packing cooling of sweet cherries as the core temperatures achieved by in-line hydrocoolers during packing do not reduce temperatures sufficiently to ensure good quality retention over longer periods of time that are required for container shipping to export markets. Therefore, forced-air cooling is recommended to further reduce sweet cherry temperatures in the box, before shipping.

Washington State University