# _Torusspora delbrueckii_ Strain Behaviour within Different
## 3 Results and Discussion
### Physicochemical Parameters  
The physicochemical parameters of the final products were measured, and are reported in Table 1. The statistic difference among the samples and correlation to yeast strain, production method, or their interaction have been measured. Most of the measured features appeared to be significantly influenced by the yeast strain and method interaction, with the exception of Brix, inorganic nitrogen content, catechins, and polyphenol content. The catechin content was significantly influenced by both the strains and the method, while the inorganic acids and the polyphenol content were significantly correlated to the methods. Even if the ANOVA analysis revealed some significant difference of pH in the cider produced in this study, the most relevant difference was detected in the base cider produced by strain A (CA) and correlated to the higher total acidity measured for CA. The total acidity was higher in CA (8.19 \(\pm\) 0.08 g/L), compared to PNA, TMA, and CMA. On the contrary, the total acidity of CB was lower (4.82 \(\pm\) 0.72 g/L) than in the related sparkling cider. Considering that the total acidity of juice was 6.5 g/L, it can be assumed that strain A has initially stimulated the synthesis of organic acids, lately consumed under CO\({}_{2}\) pressure. On the other hand, during the production of CB, organic acids were consumed and newly synthesized in the related sparkling wines. This behaviour may be associated with a strain-related response to different stress [31; 32]. The differences in the detected acetic acid and malic acid were highly significant and correlated to the yeast strain, production method, and yeast strain-method interaction. The higher amount of acetic acid was measured in ciders fermented with the _T. delbrueckii_ strain B, and we also observed a lower concentration in the base ciders in comparison with the sparkling ciders. In particular, the base ciders CA and CB had a content about 2- and 3.6-fold lower than the related TM or CM. The initial concentration of malic acid in juice (7.42 g/L) was higher than those recorded in ciders. The malic acid consumption was minimal in CA, with 6.71 \(\pm\) 0.12 g/L left, and almost total in CB, with only 0.32 \(\pm\) 0.45 g/L of malic acid left. In all sparkling ciders from both strain A and strain B, the malic acid was below the detection level. In some studies, it has been reported that _T. delbrueckii_ is able to consume malic acid as a carbon source; this behaviour is strain-dependent, and, also, it depends on nutrient availability [33; 34]. Together with malic acid consumption, the detection of L-lactic acid in all products, with the exception of CA, is suggesting the occurrence of malolactic fermentation. In addition, the presence of D-lactic acid, found in all products, can be a consequence of homo- and hetero-lactic acid bacteria metabolism [35]. The co-occurrence of acetic acid, L-, and D-lactic acid, and the little residual malic acid suggests the contemporary presence and active metabolism of the inoculate yeasts and spontaneous lactic acid bacteria already in the apple juice. \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \multicolumn{1}{c}{} & \multicolumn{3}{c}{**Significance**} & \multicolumn{3}{c}{**Stania A**} & \multicolumn{3}{c}{**Stania B**} \\ \hline  & S & M & S\&M & Base color & Pet-Nat & Churnat & Champenoise & Base color & Pet-Nat  
In all final products, the residual sugar content was below 1 g/L; therefore, in all the products, the yeast fermented all the sugars available to dryness. Despite the ethyl alcohol content in all base ciders (6.30 \(\pm\) 0.08 and 6.21 \(\pm\) 0.16% for CA and CB, respectively) being very similar to the one of the corresponding PN ciders (6.35 \(\pm\) 0.03 and 6.00 \(\pm\) 0.03% for PNA and PNB, respectively), the ethyl alcohol concentration in CB was significantly different from PNB. [PERSON] et al. [11] and [PERSON] et al.