Postharvest Quality of ‘Keepsake’ Apple Fruit

Abstract

Storage information regarding ‘Keepsake’ apple fruit is lacking. The objective of this research was to investigate the postharvest characteristics of ‘Keepsake’ apple (Malus ×domestica Borkh.), which is a parent of ‘Honeycrisp’. Apples were obtained from three orchards in Minnesota in 2022 and 2023, assessed for quality, and stored at 0 to 1 °C or 4 to 5 °C in air. Fruit were tested for firmness, soluble solids content (SSC), and titratable acidity (TA) for up to 6 months in storage. At harvest, fruit from different orchards differed in ground color, firmness, SSC, and titratable acidity. The starch pattern index did not differ among the orchards within a year, but it was greater during the 2023 harvest than during the 2022 harvest. Fruit firmness decreased less rapidly at 0 to 1 °C than at 4 to 5 °C. Changes in SSC with storage varied by orchard, storage temperature, and year. In 2022 to 2023, SSC changes were highly variable, remained the same during storage for fruit from one orchard, increased and then decreased for fruit from another orchard, increased after 1 month of storage, and then remained unchanged thereafter for fruit from the third orchard. In 2023 to 2024, SSC was generally unchanged during storage at 0 to 1 °C, and it increased slightly over time during storage at 4 to 5 °C. Titratable acidity decreased during storage, but there was no difference between storage temperatures. These findings demonstrate the difficulty determining when to harvest ‘Keepsake’ fruit because neither starch pattern index nor ground color is a reliable indicator of ripeness. Growers must rely on experience and fruit redness to determine when to harvest this late-season cultivar. To prolong fruit firmness, growers should store ‘Keepsake’ fruit at 0 to 1 °C rather than at 4 to 5 °C.