## 3 Results and Discussion
### Sensory Properties of the Detected Volatile Components  
In order to evaluate the modifications in the sensory properties of fermented _A. platensis_ in respect to the unfermented materials and to determine the changes in aromatic notes due to the different stabilization processes applied, all of the volatile compounds and their relative concentrations were grouped based on the odor type that they were able to provide. The following ten main different aroma attributes were identified: aldehyde/ethoreal, sulfurous, green/herbal, buttery/waxy, spicy, fruity, floral, nutty/roasted, alkane and fermented. On the basis of this classification, analogies and differences in odor type production among different samples were observed by applying a two way ANOVA test considering fermentation and stabilization treatments as factors (Figure 4, Supplementary Table S2). Lactic acid fermentation of spirulina biomass caused an enhancement in the aromatic profile. In particular, the fermentation process significantly influenced the concentration of those compounds responsible for aldehyde/ethereal, buttery/waxy, alkane and of course fermented aromatic notes (\(p<0.01\)). As expected, buttery/waxy and fermented notes increased with the fermentation process (Figure 4). These aromatic properties can be mainly associated with the presence of diacetyl, acetoin (buttery/waxy) and isoamyl alcohol (fermented). The concentration of all these volatiles showed an improvement in both of the stabilized materials after the fermentation process, but while in sterilized spirulina, _L. casei_ 2240 produced a higher amount of diacetyl and acetoin, in UV-treated material, _L. rhamn_ GG affected the content of these compounds more prominently (Supplementary Table S1). In addition, buttery/waxy and fermented aromatic notes were also influenced by stabilization treatment; in particular, a statistically significant interaction was observed for fermented notes of the two considered factors (\(p<0.001\)) (Supplementary Table S2). Moreover, aldehyde/ethereal and alkane attributes, provided mainly by the presence of aldehydes and hydrocarbons, were strongly influenced by the fermentation step, especially in UV-treated samples (Figure 4). It must be emphasized that hydrocarbons, and in particular heptadecane, could be associate with the off-flavor of algae [41]. Alkane attribute concentrations were also influenced by the applied stabilization method (\(p<0.01\)), as clearly represented in Figure 4. Thus, to limit the formation of these sensory attributes, sterilization must be chosen as the stabilization treatment. On the other hand, significant differences were found in the production of sulfurous, green/herbal, fruits, and nutty/roasted notes (\(p<0.02\)) among the stabilization treatments (Supplementary Table S2). The concentrations of all of these aromatic classes were statistically higher in the sterilized samples (\(p<0.02\)). High temperature can cause the formation of pyrazine and sulfur compounds associated with nutty/roasted and sulfurous notes, as well as the degradation of carotenoids and fatty acids leading to an increase in hexanal, metholanal, 1-hexanol and 1-octen-3-ol (green/herbal and earthy notes), and benzaldehyde, \(\beta\)-cyclocitral, \(\beta\)-ionone 5,6-epoxide and other compounds associated with fruity aromatic notes. In addition, a statistically significant interaction between these two factors was noted for green/herbal and fruity notes (\(p<0.001\)). Since fruity attributes are generally considered as pleasant aromatic properties, in this case, it is also possible to speculate that sterilization may represent the better stabilization treatment because it leads to an augment of this odor class [59; 77; 78; 79]. In conclusion, despite the fact that sterilization may lead to some modifications of the aromatic characteristic of the starting material, _A. platensis_, it seemed to be the best choice to reduce the initial microbial count naturally occurring in the tested samples. Fermentation by _L.