Physicochemical Characterization of the Local Apple Cultivar 'Douce de Djerba' Compared with Introduced Cultivars in Tunisia

摘要

The objective of this study was to compare the physicochemical properties of 'Douce de Djerba' apple cultivar grown in Southern Tunisia, exactly in the island of Djerba (which is known for its good organoleptic qualities) to the introduced cultivars ('Golden', 'Startcrimson', 'Anna' and 'Richared') grown in the region of Sbiba (North-West of Tunisia). Apple dry matter, total soluble solids, pH and titratable acidity were measured. Composition and level of sugars, vitamin C and phenolic compounds wereanalysed by high-performance liquid chromatography (HPLC). The content of major (Na, K, Ca, Mg and P) and minor elements (Fe, Cu, Zn and Mn) has been determined by using flame atomic absorption and the spectrophotometer method. The dry matter varied from 12.15% ('Anna') to 27.89% ('Douce de Djerba'), the soluble solids content was between 11.0 °Brix ('Golden', 'Startcrimson', 'Richared' and 'Anna') and 12.4 °Brix ('Douce de Djerba'), pH values varied from 3.81 ('Golden') to 4.25 ('Richared') and thetitratable acidity content (g 100 g"1) varied from 0.20 ('Richared') to 0.31 ('Golden'). The values of the vitamin C content (mg/g) ranged from 2.93 ('Anna') to 5.63 ('Douce de Djerba'). For all cultivars studied, the peel of the apple is richer in vitamin C than the pulp. Quantitative analysis of phenolic compounds revealed differences between pulp and peel in all cases studied. The highest levels of phenolic compounds were found in the peel. Chlorogenic acid was the major peak in the pulp for all apple cultivars studied. Significant differences were observed in the mineral contents of the apple samples. This difference between mineral contents and cultivars is reported in the literature and a comparison has been carried out with diverse fruits. In generally, apples are rich in macroelements (P, Na, K, Ca and Mg) while the microelements (Cu, Zn, Fe and Mn) are in the form of traces. AH results suggested that genotype is the main factor that determines the composition of bioactive compounds in applesand this provides important information on how to make the best use of the apple cultivars investigated.