Ripening Physiology and Storability of Saskatoon Fruit

Saskatoon (Amleanchier alnifolia Nutt.) fruit were stored into nine maturity stages based on color and size. Fruit color ranged from green (stages 1–4) to pink (5 and 6) to red (7 and 8) to purple (9). Fruit diameter of `Smoky' increased linearly as maturity advanced from 1 to 9. Fresh weight increased by 46 mg/fruit for each stage between 1 and 6, and then increased by 141 mg/fruit for each stage between 7 and 9. Firmness declined linearly from maturity 1 to 5, then remained relatively constant through maturity 9. The ability of fruit of maturities 3, 5, and 7 to ripen after harvest was assessed over 6 days (23C). Color measurements of maturities 3 and 5 indicated a change from green to pink, but no further change to purple. Color of maturity 7 changed to equal that of fully ripe (purple) maturity 9 fruit. After 6 days, fruit firmness of maturities 5 and 7 was equal that of freshly harvested maturity 9 fruit; however, maturity 3 fruit were incapable of softening to the same degree as fully ripe fruit. While fruit harvested at stage 7 appear to ripen normally, a significant lower fruit fresh weight precludes harvesting at this stage. Internal C2H4 concentration of fruit, and production by fruit in an open air-flow system, were monitored for `Northline', maturities 1–9. Internal C2H4 concentration of maturity 6 fruit was about 8-fold higher than that of maturity 4 fruit. Moreover, C2H4 production rate of maturity 5 fruit increased 3-fold from 10 to 25 h after harvest and then fell, reached the initial rate by 45 h after harvest. The respiration of these fruits also increased (by ≈70%) from 15 to 30 h after harvest, and then declined. Fruit color had changed from mostly green to red by 45 h after harvest. Collectively, these results indicate that saskatoon fruit exhibit a climacteric ripening patter. Results on the efficacy of controlled-atmosphere and hypobaric storage to delay physiological and pathological deterioration of saskatoon fruits will be presented.