Colour development and quality of mangosteen (Garcinia mangostana L.) fruit during ripening and after harvest

The colour of mangosteen (Garcinia mangostana L.) fruit changes from green to purple black after harvest as the fruit ripens, and is used as a quality guide for growers and consumers. We determined the relationship between anthocyanin composition and content during fruit colour development in relation to fruit maturity and postharvest quality. Fruit at different stages of maturity (light greenish yellow with 5% scattered pink spots to purple black) were harvested and kept at 25 °C (85–90% RH). Fruit from each maturity stage all developed to the final purple black stage. During the postharvest period, hue angle values and pericarp firmness decreased significantly, while soluble solids contents increased. Anthocyanin contents in the outer pericarp were higher than in the inner pericarp and increased to a maximum at the final colour stage. Sensory evaluation and fruit quality (hue angle values, soluble solids and titratable acidity) of fruit harvested at the different stages did not differ once the fruit had finally developed to the purple black stage. The anthocyanins in the outer pericarp mainly consisted of five compounds, identified by HPLC/MS as cyanidin-sophoroside, cyanidin-glucoside, cyanidin-glucoside-pentoside, cyanidin-glucoside-X, cyanidin-X₂ and cyanidin-X, where X denotes an unidentified residue of m/z 190, a mass which does not correspond to any common sugar residue. Cyanidin-3-sophoroside and cyanidin-3-glucoside were the major compounds and the only ones that increased with fruit colour development.