Sugar/Acid Composition and Development of Sweet and Tart Carambola Fruit

Abstract

Abstract The oxalic-acid-accumulating fruit of carambola ( Averrhoa carambola L. Oxalidaceae) was examined during development to characterize changes in sugars and acids and to evaluate potential maturity indices. Commercial maturity (color break) occurred 65 and 60 days after fruit set of sweet ‘Arkin’ and tart ‘Golden Star’, respectively. Fruit size at this stage was highly variable (51 to 103 mm long) and not a reliable indicator of maturity. Total soluble sugar concentration, mainly glucose and fructose, was almost 25% greater in the sweet ‘Arkin’ fruit (≈27 mg·g −1 fresh weight) than in the tart ‘Golden Star’ carambolas (22 mg·g −1 fresh weight). At harvest, sucrose made up only 15% to 20% of the total soluble sugars. Oxalic acid was the predominant organic acid in young fruit of both cultivars, but levels differed dramatically between sweet ‘Arkin’ (≈1 mg·g −1 fresh weight) and tart ‘Golden Star’ (≈7 mg·g −1 fresh weight). Malic acid (<1.5 mg·g −1 fresh weight) was also present. Acidity in sweet ‘Arkin’ carambolas declined rapidly during early growth, but remained high during development of tart ‘Golden Star’. Sugar accumulation, acid reduction, and color development continued for at least 7 days after color break if fruit remained on trees, but such fruit were not firm enough for typical commercial handling.