Effects of Intracellular Distribution of Sugar and Acid at Different Developmental Stages on Sweetness and Sourness of Peach Fruit

To understand the distribution and changes of sugars and acids in peach fruit during the growing stages, their distribution and concentrations in vacuoles, cytoplasm, and free space in fruits of Prunus persicae‘Hakuho’ at different growing stages were studied by compartmental analysis, and their contribution to fruit sweetness and sourness was assessed. Results showed that the concentration of sugars (sucrose, glucose, fructose and sorbitol) and acids (malate, citrate, quinate and shikimate) in vacuoles, cytoplasm and free space of mature fruits was 27.3, 11.6 and 9.0 mg/g, and 2.09, 0.94 and 0.35 mg/g, respectively, and was 0.97, 2.2 and 2.3 mg/g, and 0.25, 0.44 and 0.82 mg/g in immature fruit, respectively. Sweetness and sourness was less affected by the different distribution of sugar and acid in cells in immature fruit than that in mature fruit. There was an obvious concentration gradient between the vacuoles, cytoplasm and free space for sugars and acids, and the differences in the intracellular distribution of sugar and acid may be responsible for the changes of fruit sweetness.