## 4 Conclusions  
The results of this study showed that it is possible to produce vinegar from sweet wine made by the alcoholic fermentation of aqueous extracts of the side stream generated from Corinthian currants (FSS), using a mixed selected culture (_A. aceti_ and _K. europaeus_) and a wild AAB culture, free or immobilised on a natural cellulosic material. The cultures could be reused for repeated actification batches, which is important for the functional stability of the process. However, the recovery of the biocatalyst is easier in the case of the immobilized cells, which remain in the bioreactor while the vinegar is easily decanted and has a better clarity compared to that made by free cells. The effect of cell immobilization on the acidification kinetics was more obvious in the case of the _A. aceti_ and _K. europaeus_ culture, as well as in the case of all cultures after storage for 2 months at 4 \({}^{\circ}\)C. Specifically, cold storage of all cultures reduced their activity during the first fermentation batch, but the immobilized cells, especially of the selected culture, performed better in the subsequent fermentation batches, indicating better survival of the immobilised bacteria during storage and readaptation to the actification environment. The vinegar had a high antioxidant capacity and phenolic content and a rich volatilome. Higher percentages of esters on total volatiles were identified in vinegar made by immobilized cells, while higher percentages of alcohols were found in vinegar made by free cells of the wild culture. The results are encouraging for vinegar production from sweet FSS wine with immobilized cells of a mixed _A. aceti_ (quick fermentation starter) and _K. europaeus_ (acetic acid resistant) culture.  
The following are available online at [[https://www.mdpic.com/article/10.3390/foods10123133/s1](https://www.mdpic.com/article/10.3390/foods10123133/s1)]([https://www.mdpic.com/article/10.3390/foods10123133/s1](https://www.mdpic.com/article/10.3390/foods10123133/s1)), Figure S1: Kinetics of the actification of wine at 30 \({}^{\circ}\)C using wild AAB culture, free (FCW) and immobilized (ICW), and the mixed AAB culture (_A. aceti_ & _K. europaeus_), free (FCM) and immobilized (ICM), Figure S2: Kinetics of the actification of wine at 30 \({}^{\circ}\)C, reusing the wild AAB culture, free (FCW-2M) and immobilized (ICW-2M), and the mixed AAB culture (_A. aceti_ & _K. europaeus_), free (FCM-2M) and immobilized (ICM-2M), after 2-months of cold storage at 4 \({}^{\circ}\)C. Table S1: Parameters of the sigmoidal (Boltzmann) model curve fit of the experimental data means of 3 acidification batches (Figures 3 and 4), Table S2. Actification rates as slopes of the linear fits of the growth phases of the Boltzmann sigmoidal curves of Figures 3 and 4.  
Conceptualization, supervision, resources, A.B., A.A.K., E.K. and A.M.; methodology, investigation, data curation, I.P., A.B., A.T., A.M. and S.P.; validation, software, writing-original draft preparation, review, and editing. A.B., A.T. and S.P.; funding acquisition, A.A.K., A.B., I.P. and E.K. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Agricultural Cooperatives' Union of Aeghion S.A. (project \"Exploitation of raisin finishing side-stream\" (MIS/E420) and the \"Food Innovation Research Infrastructure\" (MIS/5027222), implemented under the Action \"Reinforcement of the Research and Innovation Infrastructure\" of the Operational Programme \"Competitiveness, Entrepreneurship and Innovation-NSRF 2014-2020\", co-financed by Greece and ERDF.  
Not applicable.  
The work was also supported by the Andreas Mentzelopoulos University of Patras Scholarships.  
The authors declare no conflict of interest.