Impact of harvest date on size, composition, and volatiles of Arkansas fresh-market blackberries

While fresh-market blackberries (Rubus subgenus Rubus Watson) can have robust flavors, fruit quality can vary during a harvest season. The impact of harvest date (early, middle, and late) on ‘Natchez’, ‘Prime-Ark^® Traveler’, and ‘Sweet-Ark^® Ponca’ grown in 2020 and 2021 at the University of Arkansas System Division of Agriculture Fruit Research Station were evaluated. Blackberries were hand-harvested on three dates one week apart and frozen (-10°C) for evaluation of berry weight, composition, and volatile attributes. In general, cultivars differed for berry weight (5-11 g), soluble solids (10-13%), pH (3.5-4.0), titratable acidity (0.5-1.0%), and solids/titratable acidity ratio (10-25), but harvest date impact varied by cultivar and year. For berry weight, the cultivar × year interaction was significant with ‘Natchez’ having 45% larger berries in 2021 (13.02 g) than in 2020 (8.97 g), but no difference for ‘Prime-Ark^® Traveler’ (~5.1 g) or ‘Sweet-Ark^® Ponca’ (~5.7 g). The cultivar × harvest date × year interaction was significant for soluble solids with most cultivars in both years having higher soluble solids at early harvest dates as compared to late harvest dates. The harvest date × year interactions were significant for pH, titratable acidity, and solids/titratable acidity ratio with blackberries from the late harvest 2020 having a higher pH and ratio and lower titratable acidity than 2021. For these blackberries, 139-165 volatile compounds were identified across 9-10 compound classes (monoterpenes, alcohols, aldehydes, sesquiterpenes, esters, ketones, fatty acids, aromatic hydrocarbons, furans, and lactones). The cultivar × harvest date × year interaction was significant for total volatiles. In 2020, ‘Sweet-Ark^® Ponca’ middle harvest date (3,977 µg kg^‑1) had the highest total volatiles, while ‘Natchez’ early harvest date (1,258 µg kg^‑1) had the lowest. In general, harvest date impact varied by cultivar and year. This research provided insight into the quality attributes of blackberries to understand how quality can vary by cultivar, harvest date, and year.