EXTENDING POSTHARVEST QUALITY OF SWEET CHERRIES:  COLD CHAIN REGIMES AND FRUIT TEXTURE COMPONENTS

Gabriela Paola Bolanos

Sweet cherry (Prunus avium L.) is a highly perishable fruit whose postharvest quality, texture, and storage potential are critical for consumer acceptance and marketability. This thesis evaluated factors affecting sweet cherry quality during postharvest storage and investigated the structural basis of texture differences among fruit tissues.The first study evaluated the effects of storage atmosphere, harvest maturity, and season on fruit quality in four sweet cherry cultivars: ‘Rainier’, ‘Bing’, ‘Skeena’, and ‘Sweetheart’. Fruit were harvested at early (H1) and commercial maturity (H2) stages during the 2024 and 2025 seasons, hydrocooled, and stored at 0.5 °C and >95% relative humidity under regular atmosphere, modified atmosphere packaging (MAP), and controlled atmosphere conditions of 11% O₂ + 15% CO₂ (CA-High) and 1% O₂ + 1% CO₂ (CA-Low). Fruit quality attributes, including color, weight loss, respiration, stem quality, stem force retention, firmness, soluble solids content, titratable acidity, and postharvest disorders, were evaluated during storage and shelf life. Harvest maturity strongly influenced initial fruit quality, with H2 fruit generally showing greater weight, skin color development, and soluble solids concentration. Storage responses varied among cultivars, maturity stages, and seasons. MAP generally maintained higher firmness and reduced weight loss, whereas CA-Low generally maintained better stem condition and, together with Control, was associated with lower respiration rates at selected evaluation times. Internal browning was more frequently associated with CA-High, particularly during extended storage. The second study examined the relationship between tissue texture, cell wall composition, and anatomy in five sweet cherry breeding selections from the WSU Sweet Cherry Breeding Program. Fruit were harvested at three maturity stages during the 2024 and 2025 seasons. External and internal mesocarp tissues were evaluated for texture, cell wall composition, and parenchyma cell area. Fruit quality traits and texture classifications changed with harvest maturity, although responses differed among selections and seasons. Cell wall fractions showed tissue- and maturity-dependent responses. Water-soluble pectins increased with maturity in several selections and were occasionally greater in soft tissue, while CDTA-soluble pectins were generally higher in external tissue. However, pectic fractions, neutral sugar fractions, alcohol-insoluble residue, and cell area did not consistently distinguish firm from soft tissues. Overall, these findings showed that sweet cherry storage performance depended on cultivar, maturity stage, season, and storage atmosphere, while tissue texture in breeding selections was associated with some changes in cell wall composition and anatomy. However, these texture-related patterns were not consistent across all selections or harvest maturities.

EXTENDING POSTHARVEST QUALITY OF SWEET CHERRIES: COLD CHAIN REGIMES AND FRUIT TEXTURE COMPONENTS

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