Lipid peroxidation and lipid-soluble antioxidants as quality control markers in cold-stored fruit for establishing commercial acceptability in Bacon avocados

Abstract

Avocados are prone to chilling injury disorders when stored at low temperatures. Although most studies have been performed in the worldwide distributed ‘Hass’ variety, other less exploited commercial varieties such as ‘Bacon’ might be more cold-tolerant. Aiming at evaluating how cold storage influences chilling injury, the extent of lipid peroxidation and the contents of lipophilic antioxidants were measured in ‘Bacon’ avocados. Harvested fruit were divided into two groups: one stored for 6 weeks at 4 °C and sampled at various time intervals for 42 days, and the other maintained at low temperatures for 3 and 6 weeks and then exposed to room temperature for 5 days until ripened. Long-term cold storage negatively influenced tocochromanols and carotenoids composition in unripen fruit, decreasing progressively both vitamin E and plastochromanol-8 contents, and most particularly carotenoids; yet chilling injury was prevented during cold storage for 6 weeks. When these fruits were ripened at room temperature, chilling injury increased 20% in the peel but only 5% in the mesocarp (edible part). Enhanced chilling injury in the mesocarp was associated with a 2.3-fold increase in lipid hydroperoxides (a primary lipid peroxidation product) and a 2.5-fold increase in plastochromanol-8 content, while contents of other tocochromanols, carotenoids and malondialdehyde (a secondary product of lipid peroxidation) kept unaltered. Interestingly, medium-term cold storage (3 weeks at 4 °C) did not lead to chilling injury in ripe fruit, therefore cold storage for 3 weeks is considered optimal to prevent large antioxidant vitamin degradation and maintain fruit quality in ripen avocados. In conclusion, despite the high cold tolerance shown by ‘Bacon’ avocados, fruit showed a strong depletion (60%) in carotenoids content after 6 weeks of storage at 4 °C, negatively affecting their commercial acceptability. Aside from evaluating visual chilling injury symptoms, evaluation of lipid peroxidation markers and contents of lipid-soluble antioxidants are deemed to be essential to establish commercial acceptability in cold-stored fruit.