Assessment of organic acid and sugar composition in apricot, plumcot, plum, and peach during fruit development

Variation in content of organic acids and soluble sugars, and in physical characteristics was evaluated in apricot (P. armeniaca L. cv. Harcot), plumcot (plum-apricot hybrid, P. salicina x P. armeniaca L. cv. Harmony), plum (P. salicina Lindl. cv. Formosa), and peach (P. persica L. Batsch cv. Jinmi). The content of organic acids and sugars, as well as parameters of fruit quality (weight, dimensions, firmness, total soluble solids, and total acidity) in Prunus fruits during fruit development were determined. Organic acids, including oxalic acid, quinic acid, malic acid, shikimic acid, citric acid, and quinic acid, sugars, including sucrose, fructose, glucose, and sugar alcohol (sorbitol), were identified and quantified using HPLC. Organic acid mostly increased during the early stages of fruit growth (30 - 60 days after full bloom) and decreased until fruits were fully ripened. In general, plum was the highest in most organic acids compared with the other fruits, while apricot contained the lowest acid content except for citric acid. Sucrose, fructose, and glucose content increased with fruit development, unlike content of sorbitol. Plumcot contained the highest fructose, and peach showed the maximum content of sucrose at full maturation stages. Total soluble solids averaged 17.5, 14.8, 11.9, and 10.6 degrees Brix in apricot, plumcot, plum, and peach, respectively, whereas total acidity was 0.9, 1.4, 0.5, and 0.3% in four Prunus cultivars at ripened stages. Shikimic acid was significantly correlated with oxalic acid in apricot, plumcot, and plum, but not in peach. Fructose and glucose were highly correlated in plumcot, plum, and peach.