Morphological characteristics, ascorbic acid and antioxidant activity during fruit ripening of four lemon (Citrus limon (L.) Burm. F.) cultivars

Citrus limon (L.) Burm contains many important natural bioactive compounds, such as ascorbic acid, essential oils, and antioxidant substances. An experiment was carried out on four lemon cultivars (Ovale di Sorrento, Sfusato Amalfitano, Femminello Cerza and Femminello Adamo) from Southern Italy to study the changes in physico-chemical properties of juice during fruit ripening. Morphological characteristics of fruits, total soluble solids, pH and titratable acidity, ascorbic acid (AsA), and antioxidant activity (TEAC) of juice were tested. The concentrations of AsA in lemon juice showed significant differences among cultivars and ripening stages, with a steadily decrease along ripening stages: from 31.38 of stage I to 23.71 mg 100 g−1 of stage IV. The juice AsA concentration correlated with the colorimetric parameters of peel: L (r = −0.643), a (r = −0.719) and b (r = −0.654). The cv Ovale di Sorrento showed the highest average AsA concentration (29.91 mg 100 g-1). The level of the total TEAC showed a significant steadily decrease from the first to the fourth ripening stage that on average approached 38 %. Principal component analysis showed that lemon fruits at the ripening stages II and III were highly similar each other and well discriminated from the first and last ripening stages that also performed more distantly each other. The paper provides in-depth knowledge about the trend in AsA content and antioxidant activity of lemon juice across ripening