## 3 Results and Discussion
### Volatile Profile
Generally, the intensity of the signals recorded for volatile organic compounds' peaks detected by chromatographic analysis showed an increase in all three series of samples from t0 to t3. This phenomenon could be linked to the proteolysis and hydrolysis phenomenon occurring toward polysaccharides and lipids during the first months of caiar aging, as previously indicated in the literature [8; 15]. However, the evolution of the whole profile of parameters measured in samples was related to the increase of different compounds for each group, and, thus, lead to the distribution of scores in different quarters of the PC space. Particularly, the NC samples clearly showed an opposite trend in comparison to the other two treatments. During the sampling time, from t0 to t3, NC samples noticeably moved toward the area of the space related to the higher loadings of many compounds indicative of the occurrence of ripening and spoilage processes: 3-hydroxybutan-2-one, 3-methylbutan-1-ol, and 2-methylhexan-1-ol. Similarly, the NC series was positively related on both PC-1 and PC-2 to the amount of viable counts detected (TVC, total viable count), showing a clear increase from t0 to t3. At t3, 3 samples out of 4 of the NC series showed the presence of microbial counts, reaching an average value of 6.89 log CFU/g. Thus, we evidenced that the NC  
Figure 1: (a) Score plot of caiar samples analyzed in the study obtained by a multilevel principal component analysis (multilevel-PCA). t-0 = unripened rose, t-1 = 4 months of caiar ripening, t-2 = 8 months of caiar ripening, t-3 = 14 months of caiar ripening. (b) Loading plot of parameters measured in analyzed caiar samples obtained by multilevel-PCA. Variables associated with higher loadings on the 1 st or the 2 nd principal component (PC-1 and PC-2 on the x and the y axis, respectively) are related to a higher influence on variability recorded among samples in the multiple level data matrix. samples at t3 showed a higher correlation with the values of all the parameters identified as markers of microbial spoilage. This outcome agreed with the fact that 14 months of storage are considered far and away the optimal ripening time for salted-only caivar from producers, usually indicated as 6-8 months maximum. The microbial counts in this study were detected at different concentrations in the three series, according to the antimicrobial effectiveness of the preservatives employed. For the OAM series, no counts were evidenced at the end of the sampling time (t3). According to this, the OAM samples (the red diamonds in Figure 1b) showed the lowest dispersion from t0 and t3 and the highest tendency to form a condensed cluster characterized by scores inversely associated with the markers of spoilage processes. In the multilevel-PCA plot, this series was positively related on the PC-1 to the loadings for many compounds, such as terpenes and organic acids, which have not been associated with the spoilage of the product. Finally, we observed an intermediate trend for the BSM series. A clear evolution was evidenced between t1 and t2 (4 and 8 months of ripening, respectively), with BSM moving toward the lower quarters of the PC space, positively related on the PC-2 with the loadings of many compounds, such as aldehydes, ketones, and alcohols, particularly 2-penten-1-ol. Then, the profile of the BSM series showed a smaller changes between t2 and t3. Actually, the time range t1-t2 was the one in which the most interesting changes on the volatile and microbial pattern was evidenced in all samples analyzed. In this time range, enzymatic, oxidative, and microbial activities took place in samples from all the series, leading to the formation of several chemical compounds responsible for the fishy flavor of caivar (2-penten-1-ol, 3-pentanone, 4-heptenal), but at a different rate in the different treatments.