Effects of storage temperature and atmosphere on saskatoon (Amelanchier alnifolia Nutt.) fruit quality, respiration and ethylene production

Abstract

Abstract Low temperature and controlled atmospheres (CA) were tested for their effectiveness in extending the storage life of saskatoon fruit. The quality of fully ripe (purple) `Smoky' and `Pembina' fruit was assessed over 40 days of storage at 0.5 or 4.0°C in humidified (95% RH) air. Fungal colonization, fruit softening, fresh-weight loss, and anthocyanin degradation were substantially lower in fruit stored at 0.5°C than in that stored at 4.0°C. `Smoky' fruit maintained higher soluble solids when stored at 0.5°C than at 4.0°C, but that of `Pembina' was not affected by temperature. Decreasing the O2 concentration from 23 to 5.8% had little effect on fruit respiration at 23°C; however, the respiration rate fell about 26% as the O2 concentration was lowered from 5.8 to 1.7%. A 2% O2 atmosphere was above the extinction point for aerobic respiration at 23°C. Fruit (cvs. `Smoky' and `Northline') of maturity classes seven, eight and nine were stored in 2, 10 or 21% O2 (0.035% CO2) at 4.0°C (95% RH), and respiration and ethylene evolution were monitored over 10 days. The rate of ethylene production by fruit of both cultivars decreased linearly with advancing maturity class and with declining O2 concentration. Furthermore, the increase in ethylene production rate of maturity class nine (fully ripe) fruit with increasing O2 concentration was less than that from fruit of maturity classes seven and eight. Respiration rates of `Northline' and `Smoky' fruit were equal at 21% O2, but `Northline' fruit had a 15% lower respiration rate than `Smoky' fruit at 2% O2. Collectively, our results show that storage at 0.5°C was more effective than 4.0°C at maintaining fresh quality of saskatoon fruit. Low O2 atmosphere (2%) effectively slowed ethylene production and fruit respiration and thus may be a beneficial adjunct to low-temperature storage.