Effects of heat shock and nitrogen shock pre-treatments on ripening heterogeneity of Hass avocados stored in controlled atmosphere

- Heat treatment followed by CA storage reduced ripening heterogeneity.
- Heat + CA presented a higher respiration rate during the first week of storage.
- Heat + CA display differences in ACO transcript accumulation.
- Heat + CA did not alter the fatty acid profile.

Hass avocado ripening heterogeneity generates logistics problems to importers and ripeners due to higher labour costs, inconsistent quality delivery and postharvest losses. The main aims of this research were: (i) to evaluate two postharvest pre-treatments (nitrogen shock N2 and heat shock) prior controlled atmosphere (CA) on reduction of ripening heterogeneity of Hass avocado without being detrimental to fatty acid profile and (ii) to study the potential metabolic processes implicated in such ripening synchronization with focus on cell wall remodelling and ethylene biosynthetic pathways. Results showed that heat shock prior to CA storage significantly reduced ripening heterogeneity in early and middle season fruit while N2 + CA did not. Pectin methyl esterase (PME) and polygalacturonase (PG) activity did not display significant differences among treatments. Additionally, none of the treatments altered the fatty acid profile. ACS transcript for early and middle season fruit kept constant during storage for heat + CA, CA and N2 + CA. ACO instead displayed less abundance after 21 d storage for all treatments of early season fruit. These results point to ripening synchronization in Hass avocado subjected to heat to be related to induction of metabolic processes related to ethylene (biosynthesis), possibly at the action level (receptors) but the efficiency of the heat treatment was related to the maturity stage of the batch.