Changes in sugars, organic acids and amino acids in medlar (Mespilus germanica L.) during fruit development and maturation

The contents of sugars, organic acids, and amino acids (after acid hydrolysis) were determined during development and maturation of medlar (Mespilus germanica L.) fruit from 39 days after full bloom (DAF) until 2 weeks after the beginning of fruit drop (161 DAF). Fructose, glucose and sucrose were identified as the principal sugars and their levels varied remarkably during development. The fructose level increased continually through development reaching its maximum by 161 DAF (1200 mg/100 g fresh weight) while the increase of sucrose reached maximum at 131 DAF and had decreased at 161 DAF. After some fluctations at 69 DAF, glucose level remained high (686 mg/100 g fresh weight) at 161 DAF, when compared with Stage IV (131 DAF). While the level of malic acid increased continually, the ascorbic acid level decreased dramatically through fruit development; both acids reached their maximum and minimum levels at 161 DAF, i.e. 428 and 8.4 mg/100 g fresh weight, respectively. The total amino acid composition also changed in decreasing trend throughout development and remained low at 161 DAF. In the ripe fruit, glutamate and aspartate were the major amino compounds identified. These changes in the identified compounds can be related to the metabolic activity during fruit development and maturation. (C) 2003 Elsevier Ltd. All rights reserved.