Evaluation of Sugar and Organic Acid Composition of Apple Cultivars (Malus domestica Borkh.) Grown in Serbia

Apple (Malus domestica Borkh.) is a widely cultivated fruit tree species valued for its nutritional and sensory properties. The global market is dominated by a limited number of cultivars selected for appearance, shelf life, and consumer preference. As a result, many traditional or autochthonous cultivars, which often possess richer phytochemical profiles and greater environmental adaptability, remain underutilized. Herein, a comprehensive study of the sugar and organic acid content of the apple pulp and leaves of 19 autochthonous apple cultivars, along with 5 standard and 6 resistant cultivars for comparison, was undertaken. Fructose (47.9–74.0 mg/g FW), glucose (16.4–33.7 mg/g FW), and sucrose (25.0–34.0 mg/g FW) were detected at the highest concentrations in the apple pulp, while sorbitol (49.9–71.5 mg/g DW) predominated in the apple leaves. Principal component analysis identified xylose, quinic acid, shikimic acid, arabinose, raffinose, malic acid, citric acid, and isocitric acid as the main factors responsible for the classification patterns among cultivars. A number of autochthonous cultivars, such as ‘Gružanjska letnja kolačara’, ‘Šećeruša’, ‘Demirka’, and ‘Hajdučica’, showed characteristics comparable to commercial cultivars such as ‘Red Delicious’, ‘Golden Delicious’, and ‘Gala Galaxy’. The obtained results empasize the value of some of the analyzed cultivars and contribute to the broader re-evaluation of the local apple germplasm.