# _Torusspora delbrueckii_ Strain Behaviour within Different
## 4 Conclusions  
In the search for new actors able to confer unique aromatic characteristic to ciders, we tested the ability of two commercially available _T. delbrueckii_ strains to ferment apple juice under different conditions. The obtained results show that both _T. delbrueckii_ strains were able to withstand high pressure and deplete all the sugars, producing a correlated amount of ethyl alcohol. The profile of volatile organic components for each yeast strain was documented as well as their capability to produce different amounts of glycerol and organic acids, offering to the cider maker the possibility to master the extract and mouthfeel using selected yeasts. Despite the differences detected in volatile organic compounds, both strains imparted sensorial characteristics dominated by a fruity/floral aroma. In conclusion, our study contributes to expand the knowledge on _T. delbrueckii_ behaviour during apple juice fermentation in relation to volatile and non-volatile metabolite production and paves the way for using _T. delbrueckii_ as a solo player to produce ciders with unique aroma profiles.  
The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app13064015/s1](https://www.mdpi.com/article/10.3390/app13064015/s1)]([https://www.mdpi.com/article/10.3390/app13064015/s1](https://www.mdpi.com/article/10.3390/app13064015/s1)), Figure S1: Experiment design and flowchart: C: base cider; PN: Pet-Nat method; CM: tank-conditioned or Charmat method; TM: bottle-conditioned or Charponeable method; A: strain A; and B: strain B; Figure S2: Fermentation monitoring shows the fermentation curve for base cider expressed as sugar consumption measured by refracometer (Brix). The recorded values have been adjusted for ethanol effect; Figure S3: (a) Volatile compounds measured by HS-SPME-GC-MS-analysis in traditional bottle-fermented cider (Champenoise) inoculated with _Toruslospora delbrueckii_ strain A; (b) Volatile compounds measured by HS-SPME-GC-MS-analysis in traditional bottle-fermented cider (Champenoise) inoculated with _Toruslospora delbrueckii_ strain B; Table S1: Physiological composition of Topaz apple juice with added yeast nutrient prior to inoculation; Table S2: (a) Volatile organic compounds in ciders produced with  
Figure 6: Sensory analysis aroma profile of the final products. PN = Pét-Nat, Char = Charmat method, and Cham = Charponeise method in cider produced after inoculum with _Toruslospora delbrueckii_ strain A (A) or strain B (B). The attributes were assessed on a continuous scale from 0 to 10, with 0 being the lowest and 10 the highest score. Perlage: effervescence intensity; persistency: effervescence persistency.  
strain A also compared to the apple juice; (b) Volatile organic compounds in ciders produced with strain B also compared to the apple juice; Table S3: Organic volatile compounds in ciders produced with two different strains of _T. delbrueckii_ and different methods to produce sparkling cider.  
Conceptualization, S.S., D.R. and L.C.; data curation, N.T.; formal analysis, M.E., P.H., C.S., B.B., S.B. and S.F.; funding acquisition, L.C.; investigation, M.E., D.R. and L.C.; methodology, M.E., D.R. and L.C.; project administration, L.C.; resources, D.R. and L.C.; supervision, S.S., D.R. and L.C.; validation, D.R.; writing--original draft, M.E.; writing--review & editing, N.T., S.S., D.R. and L.C. All authors have read and agreed to the published version of the manuscript.  
Laimburg Research Centre is funded by the Autonomous Province of Bozano. The Autonomous Province of Bolzano, Department of Innovation, Research and University is gratefully acknowledged for its financial support for the Capacity building 1 (Decision n. 1472, 07 October 2013) and the project Step-Up (Decision n. 864, 04 September 2018).  
Not applicable.  
The authors declare no conflict of interest.