Maturity, storage and ripening effects on anti-fungal compounds in the skin of ‘Hass’ avocado fruit

Abstract

Fruit rots are a major risk to the quality of avocado fruit in international trade. For New Zealand-grown ‘Hass’ fruit, rots become increasingly problematic later in the harvest season. The presence of antifungal compounds, and associated compounds, in avocado fruit skin has been long documented, with much of the research done on fruit of the cultivar ‘Fuerte’. In this paper, results are presented from an investigation of the effect of fruit maturity, storage and ripening on the concentration of the antifungal compound persin and compounds associated with its metabolism in the fruit skin of New Zealand grown ‘Hass’ avocado fruit. The persin concentration decreased markedly during maturation, with a ∼ 30% decrease in total persin (the combined persin and persenone-A), from ∼ 600 mg kg−1 at the early harvest to ∼ 400 mg kg−1 at the late harvest, approximately 4 months later. The concentration also decreased during storage and ripening, although the degree of change was dependent on the concentration present at harvest. Irrespective of harvest maturity or storage, the concentration of persin in the skin of ripe fruit did not decline below ∼ 200 mg kg−1. The epicatechin concentration declined by ∼ 17% and catechin by ∼ 50% between the early and late harvests. The total (epi)-catechin (the combined epicatechin and catechin monomers, epicatechin dimer B2, and (epi)-catechin oligomers) concentration declined by ∼ 20% between the early and late harvests, from ∼15.4 g kg−1 to 12.5 g kg−1. The changes with storage and / or ripening were of a smaller magnitude than the change with maturation. Also, the total (epi)-catechins concentration tended to increase slightly during storage. The findings are discussed in the context of the risk of rots in late season New Zealand-grown ‘Hass’ fruit based on previously described associations between changes in skin composition with fruit rot development.