Comparison of physico-chemical characteristics of myrtle at different ripening stages

The fruits of myrtle at different stages of development, namely green (G), colour break (C) and mature (M), were used to investigate the changes of fruit quality and anthocyanin composition during its development. Five anthocyanin components, such as delphinidin (Dp), cyanidin (Cy), pelargonidin (Pg), peonidin (Pn) and malvidin (Mv), were detected. Among them, the content of Dp glucoside was the highest (2.12 μg · g⁻¹) and the content of Pn glucoside was the lowest (0.17 μg · g⁻¹) at the green stage. The content of Cy glucoside was the highest (120.94 and 1,200.03 μg · g⁻¹), and the content of Mv glucoside was the lowest (19.50 and 62.72 μg · g⁻¹) at the colour break and mature stages. The single fruit weight, vertical diameter and transverse diameter at the mature stage were significantly higher than those at the colour break and the green stages by 0.87 g, 1.27 mm, 1.53 mm and 1.54 g, 3.4 mm, 3.55 mm, respectively. Fruit quality, the contents of soluble sugar and carotenoids, gradually increased with the development of fruit; and the contents were the highest at the mature stage (17.68% and 16.90 μg · L⁻¹). The contents of titratable acidity, total phenol, flavonoids, chlorophyll a and total chlorophyll gradually decreased with the development of fruit, the content was the lowest at the mature stage (2.71 mmol · 100 g⁻¹, 9.29 μg · g⁻¹, 0.1%, 0.37 μg · L⁻¹, 0.9 μg · L⁻¹) and the content was the highest at the green stage (5.25 mmol · 100 g⁻¹, 21.07 μg · g⁻¹, 0.17%, 8.86 μg · L⁻¹, 15.47 μg · L⁻¹). The difference between the green period and the colour break period was significant.