## 3 Discussion  
As described in the Introduction section, the production of sweet wines may face challenges such as the high cost of the alcohol added for their fortification or the need for osmotolerant and alcohol tolerant yeasts [11; 13; 14; 15; 16]. Fortification with alcohol may increase the production cost of a sweet wine vertically and may lead to wines being deprived of typical fermentation aromas and with imbalanced acidity (usually low) or sweetness (high) [13]. In this study, in the frame of efforts to develop added value products by the exploitation of FSS, three methods for sweet wine making are proposed and compared (Figure 1). The starting raw material was aqueous FSS extract of high sugar content (-264 g/L), and the fermentation took place by the alcohol tolerant strain _Saccharomyces cerevisiae_ AXAZ-1 [2]. The method relied on the complete conversion of sugars to produce at least 15% _v/v_ ethanol. In the dry wine that was produced, an appropriate amount of either FSS (SW-F wine) or brown syrup made from FSS (SW-S wine) were added to adjust the sweetness, post-fermentation. Therefore, these methods do not require the addition of alcohol, which would greatly increase the cost of production due to the high taxation of ethanol. Wine was also made by fortification with alcohol for comparison (SW-A wine). The lower-upper limits of the various oenological parameters of the produced wines are discussed in this section, while all analyses took place right after the wines' production (no storage or stabilization treatment applied). The concentration of ethanol in the non-fortified wines (SW-F and SW-S), obtained by complete fermentation, was in the range 15.2-15.5% (Table 1), and their residual sugar contents were in the range 115-145 g/L, which are typical levels for many sweet fortified  
Figure 3: (**a**) Sweet wines produced from Corinthian currants finishing side-stream (FSS). From left to right: SW-S: Sweet wine with added FSS syrup to adjust sweetness. SW-F: Sweet wine with added FSS raising to adjust sweetness. SW-A: Sweet wine with alcohol added to cease fermentation at the desired sweetness level. (**b**) Samples for sensory evaluation. (**c**) Spider web diagrams obtained from the descriptive sensory evaluation scores for visual, olfactory, and gustative descriptors of the sweet wines. wines produced commercially or at research level [13; 14; 19]. However, the level of sugar may be adjusted if a different protocol is followed, e.g., different amount and contact time of the added FSS to extract sugars in the wine or a different amount of added FSS syrup. The VA of the non-fortified wines was low (0.24-0.33 g/L) (Table 1), and lower than that of the SW-A wine (0.6-0.8 g/L), but all were within acceptable limits, i.e., below 1.5-2 g/L (depending on the type of sweet wine; ideally, acetic acid should not exceed 0.7 g/L in wines) [13; 19], and similar to that reported for commercial sweet wines. For example, [19] reported VA levels (av.) of 0.6-1.2 g/L for natural sweet wines obtained by different grape dehydration processes, [20] reported levels of 0.8-1.0 g/L in sweet wine exposed to different storage conditions, and [14] reported levels of 1.2-1.4 g/L in fortified raisin wines. In [2], VA levels of 0.4-0.6 g/L were reported in dry wines made from the same batch of FSS as in this study. It should be noted that FSS was also found to have a VA of 2.0 g/kg [2], which was considered indicative of microbial spoilage, and therefore, better handling of this raw material in the factory was recommended if it is destined for high-quality, added value products such as wines, syrups, vinegars, etc. [2; 3; 4]. The non-fortified wines had TTA levels in the range 7.2-7.6 g/L (SW-A wine had 6.1-6.6 g/L) (Table 1), which are within the range reported for commercial sweet wines [13]. The higher acidity of the SW-F and SW-S wines is obviously due to the addition of FSS or FSS syrup, which increased the organic acid content of the wines post-fermentation.