Written by Janet Turner, Shawn McMurtrey, and Rachel Leisso, U.S. Department of Agriculture, April 28, 2025
Sweet cherries destined for certain export markets must retain fruit and stem quality for 2 to 6 weeks postharvest and be resilient to breaks in the cold chain. Frequent introduction of new varieties requires assessment of their potential for export quality. The goal of this two-year study was to contrast traditional sweet cherry cultivars with newer sweet cherry cultivars to determine relative export suitability. Cultivars selected for evaluation were based on stakeholder input and contained early, early mid-season, mid-season, late and very late season varieties.
Export-quality sorted and packed fruit were obtained from commercial packinghouses during the 2023 and 2024 harvest season. Fruit were separated into two different treatments which included being stored at the optimal 31 °F as well as at 40 °F in modified atmosphere bags. The latter temperature simulating an extended break in the cold chain, intended to assess a variety’s resilience to adverse storage conditions.
Research results indicate that cultivar-specific increased respiration rates precede decreased fruit quality over time as fruit use their carbohydrate reserves, and that higher respiration rates at 1-week post-packing are correlated with differences of fruit quality at 4-week post-packing. Respiration rate is an indication of how quickly fruit are utilizing their energy reserves. Increased stem loss and change in fruit color (darkening) were the 4-week post-packing outcomes most closely correlated with higher respiration rates at 1-week storage.
Post-storage firmness, pitting, pebbling, cracking, °Brix, titratable acidity, color and rot were assessed for the two different storage temperatures. Input from industry members indicated that greater attention to post-storage stem quality should be included in the study. To evaluate stem quality, we measured stem weight to stem length, which indicates stem thickness and/or desiccation. Pedicel retention force was also measured (Table 1).
| Visual Quality | Indirect Sensory / Physiological | Physiological |
|---|---|---|
| Stem browning | Firmness | Respiration |
| Stem presence | Brix (soluble solids) (sweetness) | Bag atmosphere |
| Stem quality | Titratable acidity (TA) | |
| Cut stems | Pedicel fruit retention force (PRF) | |
| Pitting | ||
| Pebbling | ||
| Cracking | ||
| Rot | ||
| Color (lightness, hue, chroma) |
The use of commercially grown fruit post-commercial packing added variability to our results as preharvest management and postharvest handling (e.g., production, harvesting, cooling, grading, packaging) could not be uniformly set and controlled for statistical purposes. Consequently, study results indicate that pre-harvest and postharvest management preceding packed product influence fruit quality outcomes later in the cold chain nearly as much as varietal differences. For instance, stem weight-to-length ratio (an indicator of thickness or desiccation), stem retention, fruit cracking, pitting, and pebbling, were more greatly affected by storage temperature and other management factors and no cultivar-specific influence was apparent. However, certain stem and fruit quality attributes were varietal irrespective of storage conditions, including pedicel fruit retention force, fruit firmness, color, soluble solids content, and titratable acidity. Although cultivar-specific fruit characteristics are important, optimizing every aspect of production and postharvest management is as crucial as cultivar selection in terms of post-storage stem and fruit quality outcomes. Below, Table 2 summarizes study results to date.
| Time of Year | Cultivars Tested | Findings |
|---|---|---|
| Early Season | ‘Black Pearl’ and ‘Chelan’ | ‘Chelan’ had a higher stem weight-to-length ratio (stem thickness) at pickup, but differences were not significant after 4 weeks storage. Pedicel retention force (force required to separate stem from the fruit) was similar for both cultivars at either optimal or high storage temperatures and were the highest of all the cultivars evaluated; fruit firmness was also the highest of all the cultivars evaluated, both at pickup, and at either optimal or high temperature postharvest. Results indicate ‘Black Pearl’ is an unusually low titratable acidity (TA) cultivar; values were lowest among the varieties evaluated, both at pickup and post-storage. |
| Early mid-season | ‘Coral Champagne’ and ‘Santina’ | Of all the varieties evaluated, ‘Coral Champagne’ had the nominally lowest pedicel retention force post-storage, although this was not statistically different from ’Bing’, Regina’, or ‘Santina’. ‘Santina’ had more pitting at pickup than ‘Coral Champagne’, but post-storage, ‘Coral Champagne’ had the lowest pitting of the cultivars evaluated. ‘Coral Champagne’ (and ‘Bing’) had the lowest pebbling incidence of the cultivars evaluated. Both ‘Coral Champagne’ and ‘Santina’ had relatively lower loss of titratable acidity than many of the other cultivars evaluated. ‘Santina’ had mid-range respiration at 31 °F but the highest respiration at 1 week and 4 weeks storage at 40 °F. |
| Mid-season | ‘Bing’, ‘Cristalina’, and ‘Burgundy Pearl’ | For mid-season cultivars, ‘Bing’ is the traditional standard. Only one lot for each of ‘Cristalina’ and ‘Burgundy Pearl’ were evaluated so no statistical analyses were performed, and results could be lot specific. ‘Bing’ stem characteristics at pickup and post-storage were mid-range relative to other varieties. The single lot of ‘Cristalina’ had low stem retention, but nominally lower cracking and pitting than either ‘Bing’ or ‘Burgundy Pearl’. Firmness was nominally higher and color darker for both ‘Cristalina’ and ‘Burgundy Pearl’ relative to ‘Bing’ shortly after packing, but ‘Bing’ had higher firmness than both cultivars after a 4 week hold, both at optimal and high temperatures. ‘Bing also had the highest titratable acidity of all the cultivars evaluated, and one of the lowest incidence rates of pebbling. |
| Late-season | ‘Regina’ and ‘Skeena’ | After 4 weeks, late season cultivars ‘Regina’ and ‘Skeena’ had the highest stem thickness (potentially indicating resistance to desiccation, although percent loss of stem thickness between pickup and post-storage had weak statistical significance according to cultivar) and mid-range pedicel retention force. ‘Regina’ had the lowest firmness of the cultivars evaluated at pickup; ‘Skeena’ had higher fruit firmness post-storage than ‘Regina’, although postharvest ‘Regina’ retained firmness better than ‘Skeena’ (e.g. lost relatively less firmness). ‘Skeena’ and ‘Santina’ lost more firmness than other varieties postharvest. |
| Extra-late season | ‘Sweetheart’ | ‘Sweetheart’ is harvested so much later than other cultivars that it deserves a category of its own. The one lot evaluated indicated that ‘Sweetheart’ stems are relatively resilient to high temperature events impacting stem weight-to-length and pedicel retention force. ‘Sweetheart’ had high firmness at pickup, but also relatively high cracking and pitting incidence. With just one lot evaluated, this data should be viewed as preliminary and lot specific. |
A portion of this project has been published in the open-access journal HortTechnology: Postpacking Sweet Cherry Stem and Fruit Quality Attributes Influenced by Cultivar.
For some newer varieties, there were difficulties obtaining sufficient lots, and the research team intends to continue evaluating fruit on a limited basis to complete data collection. For comments, cultivar suggestions, and questions, please contact Rachel Leisso, Rachel.Leisso@usda.gov.
Contact
Rachel Leisso
Research Horticulturist (Postharvest)
Pacific West Area | Physiology and Pathology of Tree Fruits Research
Hood River Worksite
U.S. Department of Agriculture
Rachel.Leisso@usda.gov
Acknowledgements
The USDA-ARS Hood River Worksite team gratefully acknowledges the Oregon Sweet Cherry Commission for funding this project. We also appreciate the numerous industry and research community members who supported this project through insightful discussion and/or by assisting with coordinating product.
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