Prompt cooling reduces incidence and severity of decay caused by Botrytis cinerea and Rhizopus stolonifer in strawberry

Abstract

Delays in initiating the cooling of freshly harvested `Chandler' strawberries (Fragaria xananassa) were compared with prompt cooling to determine how such handling affected development of postharvest decays during subsequent storage and marketing. Strawberries at the three-quarter to full red ripeness stages were harvested four times between mid-June and late July, inoculated with Botrytis cinerea or Rhizopus stolonifer and then handled to simulate prompt or delayed precooling prior to storage. This was done by incubating fruit at 35 °C (95.0 °F) and 70% to 80% relative humidity (RH) for 1 or 6 hours. The fruit were then forced-air cooled to 5 °C (41.0 °F) in 1 hour and stored for 7 days at 2 °C (35.6 °F) and 85% to 95% RH, plus displayed in a simulated market at 20 °C (68.0 °F) and 85% RH for 1 day. Decay incidence increased as the season progressed. For non-inoculated fruit, prompt cooling reduced the incidence of decay by an average of 25% and the decay severity by ~24%. With inoculated fruit, prompt cooling resulted in 15% and 29% decreases in the incidence and severity, respectively, of rhizopus rot compared to delayed cooling, and 5% and 22% decreases in the incidence and severity, respectively, of botrytis rot. Overall, the incidence of botrytis and rhizopus fruit rot averaged 60% and 85% in the prompt and delayed cooling treatments, respectively. Although prompt cooling is important for minimizing postharvest decay of strawberries, temperature management alone may not sufficiently control postharvest decay when decay pressure is high.