# Functional Characterization of _Saccharomyces_ Yeasts from Cider Produced in Hardanger
## 4 Conclusions  
A fermentation screening of six _S. cerevisiae_ and fourteen _S. warrant_ strains isolated from ciders produced in Hardanger [4] provided information on metabolic capabilities with an emphasis on aroma production. This is a first selection small-scale fermentation experiment with chemical characterization and is a stepping stone for the selection process of indigenous yeasts from Hardanger with respect to their suitability for cider production. Using the HPLC-UV/RI and HS-SPME/GC-MS methods for chemical characterization of cider produced with different strains tested, we determined seventeen AAs, two BAs, four organic acids, ethanol, glucose, fructose, and twenty-six volatile compounds, including eighteen esters (seven ethyl esters of fatty acids, two ethyl esters of branched acids, and nine acetate esters), three C6 alcohols, and five volatile phenols. In addition, in the current study, we also successfully implemented a new analytical approach for the simultaneous determination of AAs and BAs using the HPLC-UV system. When statistical analyses were applied to the obtained chemical data, cluster analysis allowed us to divide the _Saccharomyces_ strains into four main groups. The yeast groups differed in the production of aromatic components. Two groups produced few aromatic compounds. The other two groups, primarily consisting of _S. warrant_ strains, were good producers of aromatic components; one was characterized by the highest production of acetate esters, while the other exhibited the highest production of ethyl esters, volatile phenols, and C6 alcohols. Additionally, with PLS regression, we established a relationship between aroma compounds and predictor variables (AAs, BAs, organic acids, sugars, H\({}_{2}\)S production, and CO\({}_{2}\) release), and the obtained VIP scores showed that the most important predictor variables affecting aroma compounds were 16, most of which belong to the following AAs: phenylalanine, asparagine, aspartic acid, tryptophan, histidine, valine, methionine, serine, glutamic acid, glutamine, and proline. Further detailed studies on the representatives of the four yeast groups identified in our study during the fermentation process on larger scales, including sensory evaluation, are needed to find an alternative _Saccharomyces_ yeast for potential cider production from Hardanger. **Supplementary Materials:** The following supporting information can be downloaded at [[https://www.mdpi.com/article/10.3390/](https://www.mdpi.com/article/10.3390/)]([https://www.mdpi.com/article/10.3390/](https://www.mdpi.com/article/10.3390/)) fermentation090824/s1, Table S1: Yeast strains used in the study. Table S2: Calibration parameters for sugars, acids, and ethanol by HPLC-UV/RI method. Table S3: Gradient profile of HPLC-UV method for determination of amino acids and biogenic amines. Table S4: Calibration parameters for amino acids and biogenic amines detected by HPLC-UV method. Table S5: Physicochemical parameters of apple juice used in the study. Values represent the mean \(\pm\) SD for three replicates. Table S6: Content of amino acids (mg/L) and biogenic amines (mg/L) in ciders produced from apple juice fermentation carried out by 19 _Saccharomyces_ strains. Table S7: Content of organic acids, sugars, ethanol, and other measured parameters (CO\({}_{2}\) release) in ciders produced from apple juice fermentation carried out by 19 _Saccharomyces_ strains. **Author Contributions:** Conceptualization, A.H., B.M.V. and L.B. ; Data curation, U.C., I.O., B.M.V. and L.B. ; Formal analysis, U.C., M.M., T.R.V. and A.H.; Funding acquisition, I.O. ; Investigation, U.C. and L.B. ; Methodology, L.B. ; Project administration, I.O., B.M.V. and L.B. ; Resources, I.O., B.M.V. and L.B. ; Supervision, B.M.V. and L.B. ; Validation, U.C., M.M., T.R.V., A.H. and L.B. ; Visualization, A.H. and L.B. ; Writing--original draft, U.C., A.H., B.M.V. and L.B. ; Writing--review and editing, M.M., I.O., A.H., B.M.V. and L.B. All authors have read and agreed to the published version of the manuscript.