## 3 Discussion
Additionally, the TTA of the FSS extracts had been adjusted before the fermentation by the addition of tartaric acid, as described in the Section 4, contributing to the final TTA of the wines. Acidity adjustment is important for both balancing the taste of the wines as well as for better resistance to spoilage [13], and is usually performed in the must to achieve a TTA level of 5.5-8.5 g/L (red wines being more appreciated at the lower end). However, the pH levels of all three wines are quite high for the given TTAs; therefore, this is an observation that should be further investigated, as a pH above 3.8 may provide a flat taste to the wine [13]. Other authors reported TTA levels (av.) of 4.6-9.1 g/L [19], 5.2-5.4 g/L [20], and 3.3-4.5 g/L [14], while dry wines made from the same batch of FSS [2] and the same yeast (free or immobilized) had TTA levels in the range 3.8-4.3 g/L (after stabilization treatments). Among the wines, SW-A contained the lowest quantities of specific organic acids, as analyzed by HPLC (Table 1). Moreover, high levels of succinic (1.9-2.9 g/L) and malic acid (3.2-3.7 g/L) were found in all three wines, as previously reported [2] for dry FSS wine made by a more dilute FSS extract (11.3 \({}^{\circ}\)Be) (0.3-1.6 g/L malic acid, and 0.5-2.0 g/L succinic acid, after the post-fermentation treatments). Although the differences in organic acid concentrations among the samples were significant, they were at levels commonly found in wines. For example, [14] reported succinic acid levels (av.) of 0.2-0.3 g/L in sweet raisin wines produced by two osmotolerant strains in free and immobilized form. The TPC of the sweet wines was at levels usually found in white and rose wines [21]. Red sweet wines usually contain a much higher phenolic content (e.g., 894-3241 mg GAE/L [22] due to their production method (fermentation in the presence of grape marc). The SW-F and SW-S wines contained higher a TPC (in the range 280-330 mg GA/L) than SW-A (2.39-2.49 mg/L) (Table 1), obviously due to the addition of FSS or FSS syrup. Specifically, syrups made from the same FSS batch, condensed at a density of 38-40 \({}^{\circ}\)Be (65.4-69.4% sugar), had TPC levels (av.) of 1340-2133 mg/L [4], while FSS itself has 4760 mg/kg, as determined in its aqueous extract by the Folin-Ciocalteu reaction [2]. It should also be noted that the Corinthian currants are dark, almost black, grapes, but the produced wines, as in the case of most dried grape wines, are not red in color but have more yellow-brown (amber) shades [2; 17] due to their dehydration process that affects the color imparted by the polyphenols of the skins (browning reactions). The wines were additionally analyzed for polyphenol content (PPC) by a method based on the reduction of Fe(III). The PPC in the non-fortified wines was found to be 550-581 mg/L, also higher than that of SW-A (454-464 mg/L) (Table 1). The AC of the non-fortified wines SW-F and SW-F (23.8-35.6 mg AA/L) was also higher than that of SW-A (17.6-18.4 mg AA/L) (Table 1), which is consistent with their higher TPC of PPC. Dry wines previously produced by the same batch of FSS and yeast strain had AC levels (av.) of 21.0-26.3 mg AA/L [2]. In all cases, the non-fortified wines had better characteristics in terms of their antioxidant and phenolic contents. Therefore, the wine production method has a significant impact on these nutritionally important characteristics. Regarding the volatilome of the wines, it can be observed that higher amounts of esters were contained in SW-A (72.1%), compared to SW-F (45%) and SW-S (44%) (Table 2), indicating that they were contained in the alcohol used for the fortification of this wine. Higher amounts of alcohols (45-51%) were contained in SW-S or SW-F, also indicating an effect of the complete fermentation process applied in the production of these wines. The total volatile organic acid levels were similar in samples SW-S or SW-A (2.1% and 2.3%, respectively), with lower levels found in SW-F (1.3%).