## 4 Discussion
Still, it is likely that the high initial levels of the three species in the dough led to a series of positive interactions [32], resulting in rapid dough acidification. In addition, this effect was more pronounced when _L. mesenteroides_ was inoculated individually (C1). During the fermentation process, the B2 trial (_S. cerevisiae_ + _P. terrestris_) exhibited the highest CO\({}_{2}\) production compared to the C2 control (_S. cerevisiae_), aligning with the findings of [PERSON] et al. [19]. The treatments inoculated with _L. mesenteroides_ (C1 and B1) exhibited reduced CO\({}_{2}\) production, attributed to the lower metabolic activity of the LAB starter strain compared to the CO\({}_{2}\) production observed in the _S. cerevisiae_ trial. This phenomenon is expected, as yeasts typically produce more CO\({}_{2}\) than LAB [33]. However, extending the fermentation time to 12 h resulted in comparable CO\({}_{2}\) emissions in doughs inoculated with _S. cerevisiae_ (C2, B2, and B3), both in doughs with only _P. terrestris_ (B2) and in mixed inoculation conditions (_S. cerevisiae_ + _L. mesenteroides_ + _P. terrestris_) in the B3 treatment. [PERSON] et al. [34] demonstrated that _S. cerevisiae_ positively impacts CO\({}_{2}\) production, whether in sourdough starter, co-inoculated with lactobacillus, or as a single inoculum. Non-_Saccharomyces_ yeasts generally have lower CO\({}_{2}\) production capacity, minimally affecting the overall fermentation process. There is, however, a discrepancy regarding the interaction between brewer's yeast and LAB. [PERSON] et al. [35] reported that _S. cerevisiae_ and hetero-ferntative LAB equally contribute to CO\({}_{2}\) production, while other authors, including [PERSON] et al. [36; 37] and [PERSON] et al. [38], have suggested that yeasts produce more CO\({}_{2}\) than LAB. This discrepancy explains why some bakers add _S. cerevisiae_ to sourdough to address leavening issues [34]. Indeed, the highest volume increase was observed in doughs inoculated with _S. cerevisiae_ (C2 and B2), and _P. terrestris_ did not influence this parameter; however, after 9 h, the volume increase was lower in the B2 trial co-inoculated with _S. cerevisiae_ and _P. terrestris_. This is consistent with [PERSON] et al. [27], who reported a slight volume reduction in dough inoculated with _S. cerevisiae_ and _T. delbruekii_ in a 1:1 ratio. The color of the breads' crust and crumb after baking was influenced by the type of co-inoculum, with significant differences observed in the L*, a*, and b* coordinates used to define the CIELAB space. Despite these differences, the effect of _P. terrestris_ on the crust and crumb color was not significant. The variations were attributed to the starter strain used. Both _L. mesenteroides_ and _S. cerevisiae_ shifted the crust and crumb color toward white but with a lower brightness level based on the L* coordinate values. This trend is also consistent with the findings of [PERSON] et al. [39]. Specific volume analyses revealed that the trials in which _S. cerevisiae_ was inoculated exhibited the highest values (C2, B2, and B3). Although the B2 trial also included _P. terrestris_, and in the B3 trial there were both _P. terrestris_ and _L. mesenteroides_, the C1 (_L. mesenteroides_ alone) and B1 (_L. mesenteroides_ co-inoculated with _P. terrestris_) trials demonstrated that the increased specific volume was mainly due to _S. cerevisiae_. These findings are in line with those reported by [PERSON] et al. [8], where a trial fermentation conducted with a commercial _S. cerevisiae_ strain showed a higher specific volume than that fermented by non-_Saccharomyces_ strains. Analyzing the crumb image of different experimental breads is a key parameter in determining product quality after baking [40]. Several authors have indicated that void fraction, cell density, and mean cell area are primarily influenced by factors related to the type of flour and the dough production processes [41].