‘Hass’ avocado quality as influenced by temperature and ethylene prior to and during final ripening

Authors: ARPAIA, MARY LU - Kearney Agricultural Center; COLLIN, SUE - Kearney Agricultural Center; SIEVERT, JAMES - Kearney Agricultural Center; Obenland, David - Dave

Submitted to: Postharvest Biology and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/13/2018
Publication Date: 3/20/2018
Citation: Arpaia, M., Collin, S., Sievert, J., Obenland, D.M. 2018. ‘Hass’ avocado quality as influenced by temperature and ethylene prior to and during final ripening. Postharvest Biology and Technology. 140:76-84. https://doi.org/10.1016/j.postharvbio.2018.02.015.
DOI: https://doi.org/10.1016/j.postharvbio.2018.02.015

Interpretive Summary: Avocados are often held commercially for short periods at relatively high temperatures immediately after harvest but the effect on quality was not known. To address this question, avocados were harvested at five different times during the commercial season and held at 20, 25, 30 or 35 °C for 24 or 48 hours prior to storage and final ripening. Results showed that even a 24 hour exposure to 25 °C or above inhibited ripening and caused more decay to occur. Temperature during final ripening was also shown to be important as when 20 °C was exceeded discoloration of the flesh became evident, although flavor was found to be relatively insensitive to ripening temperature up to 25 °C. Results from this study provide guidelines to the avocado industry for temperatures immediately after harvest and during final ripening that will ensure optimum avocado quality.

Technical Abstract: Avocados (Persea americana Mill.) are often held for short periods after harvest at relatively high temperatures both in the field and in storage during preconditioning and prior to ripening with unknown effects on subsequent quality. To address this question, avocados were harvested at five different times during the commercial season and held at 20, 25, 30 or 35 °C for 24 h or 48 h, with and without ethylene. During the subsequent season the experiment was repeated, but without the 30 and 35°C treatments. In both seasons, following short-term temperature treatment, fruit were either immediately ripened or stored for 14 d at 5 °C and then ripened to determine the influence of storage. After final ripening to eating firmness (4.4 - 6.7N) the fruit were evaluated for quality parameters. Results from the first two seasons showed that even a 24h exposure to 25 °C and above was sufficient to inhibit subsequent ripening and enhance the occurrence of postharvest disorders such as stem end rot and body rot. Application of ethylene during the short-term temperature exposure was ineffective in preventing the disorders. In the third season of the study the effect of prolonged exposure to temperature on final ripening was examined. Although there had been research done in the past on this subject, prior work had not examined the effect of different ripening temperatures on flavor. Avocados were harvested at seven harvest dates, stored for either 4 d or 11 d at 5 °C and then ripened to eating firmness at temperatures ranging from 15 to 25 °C. Increasing temperatures up to 20 °C decreased ripening time, beyond which there was no further change. Avocados ripened at temperatures above 20 °C had an increased incidence of the development of pink discoloration in the mesocarp. Ripening temperature had no effect on overall likeability, or ratings of grassy or rich flavor. This correlated with a lack of clear effect of ripening temperature on aroma volatile content of the fruit. Panelists found fruit ripened at temperatures of 20 °C and above to be slightly less creamy that those ripened at 15°C but this had no influence on likeability. This study strongly indicated the importance of maintaining the temperature of avocados at or near 20 °C both as soon after harvest as possible and during final ripening in order to optimize postharvest quality.