## 3 Results and Discussion
### Volatile Profile  
Results of the VOCs profile detected by HS-SPME-GC-MS at different times of ripening for each treatment are presented in Tables 3 and 4. Generally, we observed an enhancement of total VOCs amount during the sampling time in all the treatments tested. Aldehydes represented the first group for quantity, followed by alcohols (in all series), ketones (only in NC series), and acids (only OAM series). In all the series, sampling time matching 8 months of storage (t2) was detected as a \"critical\" time point, characterized by a massive enhancement of the signal provided by the VOCs detected, as a consequence of the development of volatile profile because of the ripening processes that occurred. This outcome is particularly interesting since the time corresponding to 6-8 months of ripening is considered by the producers as the optimal time range to obtain high-quality caviar for all the three treatments. Many compounds were found in all the treatments tested. Some of them were detected earlier at t0, then recorded in fluctuating amounts during the storage: 3-methylbutanal, benzaldehyde, octanal, nonanal, 2-phenylacetaldehyde, decanal, and nonanoic acid. Others were merely detected during the progression of the storage, as an outcome of the ripening processes: 2-methylbutanal, 3-methylsulfanylpropanal, heptanal, 2-hexenal, 2-nonenal, 4-methyl-1-heptanol, 6-methyl-1-octanol, and 1-phenylethanone. Most of these compounds are known to belong to the typical volatile profile of fish products, as all of them had been previously found as characteristic volatile in fish products [28; 29; 30; 31; 32], and also in ripened fish roes [18; 33; 34]. 2-methylbutanal, 3-methylbutanal, 2-phenylacetaldehyde, and 3-methylsulfanylpropanal are Strecker aldehydes, known to be formed by the breakdown of amino acids: isoleucine for 2-methylbutanal, leucine for 3-methylbutanal and phenylalanine, and methionine for 2-phenylacetaldehyde and 3-methylsulfanylpropanal [35; 36; 37; 38]. 2-methylbutanal and 3-methylbutanal were found by [PERSON] et al. [39] only in fish tissue models inoculated with bacterial strains, implying that these compounds were specific metabolites produced by the microbial spoilage. On the contrary, hexanal, heptanal, octanal, nonanal, and decanal were found by the authors also in non-inoculated samples, suggesting an enzyme-catabolic or oxidative origin. Actually, most of the saturated and unsaturated aldehydes ranging from 6 to 10 carbon atoms are secondary products of oxidation and enzyme-catabolism of polyunsaturated fatty acids (PUFA): heptanal, octanal, nonanal, decanal, 2-nonenal, and 2-hexenal, found in caviar in this study, are known to derive from the degradation of oleic, linoleic, linoleic, EPA, and DHA fatty acids peroxides [35; 40]. During the storage, carbohydrates, amino acids, and lipids act as substrate for degradation processes promoted by microbial or oxidation spoilage. The rate of lipid oxidation is affected by several factors, including fatty acid composition and the unsaturation degree [35]. White sturgeon caviar contains 40% of PUFA over the total of fatty acids, with half of them being represented by n3-series FA [41]. For this reason, it can be deduced that the high unsaturation degree, associated, in many samples, with the presence of microbial strains, could have promoted the formation of secondary oxidation products with volatile properties, and probably had an impact on caviar flavor [35].