## 3 Results and Discussion
### Volatile Profile
4-heptenal is an n3-series PUFA oxidation product previously found in other fish products [29; 43; 48] and ripened fish roes [33; 34], well known to contribute to the expression of the overall cold stored and \"fishy\" flavor [49; 50]. The absence of this compound in the OAM cavair samples suggests that oxidation phenomena occurred to a lesser degree in this series, probably because of the combination of the strongly controlled storage conditions and the efficiency of the preservative added, containing isoascorbic acid as an antioxidant. In a similar way, other compounds were found in the OAM series arising later during the storage time if compared to salt and BSM series. 1-penten-3-ol and 2-ethyl-1-hexanol were detected at t1 in NC and BSM while they appeared only at t2 in OAM samples. Similarly, 2,4-heptadieneal, 2-octenal, and 1-octen-3-ol arose in NC and BSM samples at t2, but in OAM samples only at the end of the storage (t3) and in lower concentrations. These compounds are known to be related to the oxidation processes that occurs toward long-chain PUFA, and they have been found in the volatile profile of several fish products, also during cold storage [28; 29; 32; 51; 52] and also in ripened fish roes [33; 34]. 1-penten-3-ol and 2,4-heptadieral are listed among the main products of n3-series PUFA autoxidation [40]; similarly, 1-octen-3-ol is known to be a degradation product of n6-series PUFA hydro peroxides (mainly, linoleic and arachidonic acid) [53]. Moreover, 2,4-heptadieneal and 1-penten-3-ol have been evidenced as markers for early oxidation in n3- PUFA-enriched fish products, contributing to the sensorial property of rancidity and representing important contributors to off-flavors. Since some authors suggested that 1-penten-3-ol can be produced by microorganisms arousing amino acids and lipids degradation [46; 54], it has been pointed to as an indicator of microbial spoilage as well. Actually, in papers published in 2008 and 2009, [PERSON] et al. [28; 55] showed that the presence of 1-penten-3-ol and 1-octen-3-ol in fish tissues was strongly correlated with the extent of fish oxidation phenomena occurring during the storage. Furthermore, in this study, the alcohol 2-ethyl-1-hexanol was found with a decreasing trend (between t1 and t2 in NC samples, \(p<0.01\)) or completely disappearing (in BSM and OAM at t2 and t3, respectively) during the storage of caviar samples, according to what was previously found in literature [32; 45]. 2-ethyl-1-hexanol is known to be formed during the storage of fish products in vacuum conservation conditions and at low temperatures [44; 45]. [PERSON] et al. [39] found this alcohol in both microbial-inoculated and non-inoculated fish tissues, suggesting that it could be a product of both non-microbial and microbial activity, but they detected significant higher amounts of this alcohol in microbial spoiled samples. According to this, we found the highest amount of 2-ethyl-1-hexanol in NC and BSM samples at t1 (5.87 and 5.70 Log peak area), while in the OAM samples, it was found only at t2 (5.31 Log peak area). The fact that 4-heptenal, 2,4-heptenal, 1-penten-3-ol, 1-octen-3-ol, and 2-ethyl-1-hexanol were belateldly detected in the OAM series again agreed to the delayed process of oxidation hypothesized for caviar treated with this preservative. In Figure 1a,b, the score plot (a) and the loading plot (b) obtained after the employment of a multilevel principal component analysis on the whole dataset (VOCs, pH, a\({}_{\text{w}}\), microbial enumerable counts) are reported. Figure 1: _Cont._  
Changes in caiar chemical and microbiological profile occurred during the ripening time, and a tendency to form clusters among samples belonging to the same treatment can likely be observed in the multilevel-PCA score plot (Figure 1a). For all three series (NC, OAM, and BSM), an evolution from t0 and t3 was observed.