Harvest maturity highly affects fruit quality attributes of ethylene-treated ‘autumn sense’ hardy kiwifruit

Abstract

Optimal harvest date is an important quality parameter for hardy kiwifruit. We, therefore, examined the ideal harvest date to obtain high-quality ripe “Autumn sense” hardy kiwifruit. The fruit was harvested at four different harvest maturity stages [6.2%, 7.1%, 8.1%, and 9.1% average soluble solids content (SSC); H1, H2, H3, and H4, respectively], then treated with exogenous ethylene at ambient temperature, to examine the quality of the ripening fruit. The four harvest maturity stages differed significantly in firmness, SSC, titratable acidity (TA), and SSC/TA ratio, both in freshly harvested and ripe hardy kiwifruit (p < 0.001). Fruit firmness at harvest gradually decreased from 32.1 to 25.1 N, while SSC increased steadily as harvest maturity increased. TA increased steadily from 0.8 in H1 to 1.1% in H3, and was lower in H4. After ethylene treatment, the range of firmness was much lower, at 2.7–3.1 N, while SSC increased significantly from 15.1% in H1 to 16.4% in H4. TA decreased significantly from 1.0% at harvest to 0.7% after ethylene treatment, regardless of harvest maturity stage. For H3 fruit, TA was 56% lower after ethylene treatment than before treatment. After treatment, H3 had the highest SSC/TA (p < 0.001). Consumer preference was higher for H3 and H4 than H1 and H2, and was highly correlated with the SSC/TA ratio at harvest and after ethylene treatment, and with SSC at harvest. These results suggest that TA, SSC, and SSC/TA should be considered for determining the optimal harvest maturity for hardy kiwifruit. This study reveals that the quality of ripened hardy kiwifruit can be maximized by controlling harvest maturity.