COMPOSITIONAL CHANGES DURING THE FRUIT-DEVELOPMENT OF 2 PEACH CULTIVARS DIFFERING IN JUICE ACIDITY

Changes in metabolites were studied during the fruit development of tw o greenhouse grown peach [Prunus persica (L.) Batsch] cultivars with l ow acidity ('Jalousia') or normal acidity ('Fantasia'), Both cultivars had the same sucrose concentration in fruit mesocarp at maturity. In the fruit juice, pH was higher and titratable acidity was lower for 'J alousia' than for 'Fantasia' from 80 days after bloom to maturity. At four different times during fruit development, in vivo C-13 NMR spectr oscopy was used to measure the vacuolar pH of fruit mesocarp. At 55 da ys after bloom, the vacuolar pH of fruit mesocarp was not significantl y different between 'Jalousia' and 'Fantasia', whereas the juice pH wa s different between cultivars. The three major organic acids in fruit mesocarp were malic, citric, and quinic acids for both cultivars, Citr ic acid concentrations were similar in both cultivars until approximat e to 85 days after bloom and then became significantly higher in 'Fant asia'. A significantly higher concentration in malic acid in 'Fantasia ' than in 'Jalousia' was observed from the end of the first growth pha se to maturity. At maturity, 'Fantasia' fruit had two and five times m ore malic and citric acid, respectively, than 'Jalousia' fruit. The di fferences observed between 'Jalousia' and 'Fantasia' fruit for melic a nd citric acid concentrations accounted for the difference in titratab le acidity. The differences in acid concentration appeared during the plateau between the two rapid growth phases of the fruit, i.e., far be fore the onset of maturation. The three major amino acids were asparag ine, glutamic acid, and proline for both cultivars, Their concentratio n followed similar patterns in acid and low-acid fruit.