Abstract:

Three elite Jincheng varieties selected from Jiangjin sweet orange, including a low-acid (long-leaf), a normalacid
(Jincheng) and a high-acid (Daguo) cultivar, were used as materials to analyze the dynamic changes in fruit quality and
organic acids including citric acid, quinic acid and malic acid in their juice after the expanding phase. Results showed that the
size of fruit of three cultivars almost reached the maximum in late October and the total soluble solids (TSS) was gradually
increased with a decrease in titratable acid (TA). Of three organic acids, citric acid was the most dominant. During fruit
development, the content of citric acid gradually declined while malic acid showed the opposite trend; the content of quinic
acid was greatly fluctuated as it was increased in the earlier stage and then decreased, and finally reached the maximum in the
middle of November. At maturation, the fruit weight and the citric acid content of Jincheng were both in between ‘Long-leaf’
orange and ‘Daguo’ Jincheng orange, and its TSS content was highest. The fruit weight of Long-leaf was lowest (155.27 g),
and the same was true for the TA (0.55%) and the citric acid content (6.95 mg/g); on the contrary, the fruit weight (311.92 g),
TA (titratable acidity) (1.02%) and citric acid content (11.72 mg/g) of ‘Daguo’ Jincheng orange were highest among three
cultivars. These data showed a tendency that the higher TA was, the higher citric acid content and the lower quinic acid
content occurred.

Key words: sweet orange, fruit quality, organic acid components