Studies on quality of southern highbush blueberry cultivars: effects of pulp temperature, impact and hydrocooling
With increasing production of southern highbush blueberries in mild temperate and subtropical climates, growers with small acreages face several challenges to maintain fruit quality following harvest. Studies were undertaken to investigate effects of delays to cooling, pulp temperature at impact and potential for hydrocooling. Commercial cultivars 'Windsor' and 'Farthing' were harvested directly into rigid, hinged clamshell containers (0.45 kg capacity) and returned to the laboratory. There was no difference in weight loss (n=3 clamshells) loss during 3 h at 22°C (‹1%); however, after 4 h, weight loss for 'Windsor' dramatically increased to 10%, whereas 'Farthing' remained ‹1%. Condensation formed on 'Windsor' fruit in field lugs within 30 min of harvest during handling at ambient temperatures (›30°C), supporting the grower's observation for this cultivar. In a separate test these cultivars were equilibrated to 10 or 20°C, then dropped 60 cm onto a solid surface. After 4 days at 5°C, pulp temperature at impact had no effect on cumulative weight loss, fruit firmness or SSC/TTA ratio. However, firmness measurements determined that 'Windsor' was more sensitive than 'Farthing' to impact, where readings for impacted fruit of the former were 27% lower than those of undropped control fruit. In another test, both cultivars were equilibrated to 30, 10 or 5°C, and then dropped as above. Both cultivars responded similarly: when dropped at 30°C, the respiration rate and ethylene production were approximately 2.5 times higher than undropped; there was no significant difference in respiration or ethylene for fruit impacted at 10 or 5°C. 'Windsor' also demonstrated propensity to lose more weight than 'Farthing', 'Emerald' and 'Jewel' during storage at 1°C following hydrocooling. After 14 days of storage 'Windsor' had 100% shrivel and almost 5% decay, while the other cultivars averaged 43% shrivel and had no decay. These results demonstrate that these cultivars have different responses to postharvest environmental conditions that must be taken into account in order to best maintain fruit quality.
Sargent, S.A., Berry, A.D., Brecht, J.K., Santana, M., Zhang, S. and Ristow, N. (2017). Studies on quality of southern highbush blueberry cultivars: effects of pulp temperature, impact and hydrocooling. Acta Hortic. 1180, 497-502
respiration, ethylene, flavor