## Materials and Methods
### Volatile Organic Compounds Profile  
For each sample, an aliquot of 5 g of caviar was employed in the analysis without any treatment before volatile organic compounds (VOCs) extraction; each sample was analyzed in duplicate. VOCs were extracted by means of the solid phase microextraction (SPME) technique employed on the sample headspace (HS); then, analytes were separated and identified by gas chromatography coupled to mass spectrometry (GC-MS). The analytical conditions (SPME, GC, and MS parameters) were set according to the optimization used in [PERSON] et al. [18]. Briefly, DVB/CAR/PDMS 1 cm SPME fibers (Supelco) were used for the HS extraction, performed for 30 min at 60 \({}^{\circ}\)C. Then, VOCs were recovered by thermal desorption in the S/SL injection port of the GC system (6890 N Network GC system by Agilent Technologies) set at 250 \({}^{\circ}\)C, in splitless mode. The chromatographic separation was performed by an optimized oven temperature program (from 35 \({}^{\circ}\)C to 150 \({}^{\circ}\)C at 5 \({}^{\circ}\)C/min and then to 260 \({}^{\circ}\)C at 10 \({}^{\circ}\)C/min) employing a DB-5 MS column (30 m \(\times\) 0.25 mm id, 0.25 um film thickness, Agilent Technologies). Helium was used as carrier gas, at a flow of 1 mL min\({}^{-1}\) (pressure 6.71 psi). A 5973 Network Mass Selective Detector (Agilent Technologies, Inc., Santa Clara, CA, USA) was employed for VOCs detection and identification, working in EI mode (70 eV, scan range m/z 35-300 amu, scanning rate 5.19 scans sec\({}^{-1}\)). Data were acquired by Enhanced ChemStation software (Agilent Technologies, Inc., Santa Clara, CA, USA). A first tentative identification of key aroma compounds was performed by comparisons with mass spectra of compounds found in library data (NIST MS library). Then, the identification was performed by means of two approaches:  
\begin{table}
\begin{tabular}{c c c c c c c} \hline  & & & **March 2019** & **July 2019** & **November 2019** & **May 2020** \\  & & & **Raw Eggs** & **4 Months** & **8 Months** & **14 Months** \\ \hline ID & Series & Can & t0 & t1 & t2 & t3 \\ \hline
1 & & & 500 g & \(n=2\) & \(n=2\) & \(n=2\) & \(n=2\) \\
2 & _NC_ & & & & & \\
3 & 3.8\% & & 1800 g & \(n=2\) & \(n=2\) & \(n=2\) \\
4 & & & & & & \\ \hline
1 & & & & & & \\
2 & _OAM_ & 500 g & \(n=2\) & \(n=2\) & \(n=1\) & \(n=2\) \\
3 & 4\% & & & & & \\
4 & & & 1800 g & \(n=2\) & \(n=2\) & \(n=1\) & \(n=2\) \\ \hline
1 & & & 500 g & \(n=2\) & \(n=2\) & \(n=1\) & \(n=2\) \\
2 & _BSM_ & 3.8\% & & & & \\
3 & & & 1800 g & \(n=2\) & \(n=2\) & \(n=1\) & \(n=2\) \\ \hline
4 & & & & & & \\ \hline  & N= & & 12 & 12 & 8 & 12 \\ \end{tabular}
\end{table}
Table 1: Samples collection scheme. Legend: NC, sodium chloride (NaCl); OAM, organic acid mixture; BSM: borax and salt mixture.  
Identification by matching with [PERSON] and [PERSON] [19] retention indices, calculated on the basis of a homologous series of n-alkane injected in the same analytical conditions of samples [20];
2. Identification by mass spectra of authentic standards injected in the same analytical conditions, when available. When analyzing the chemical standards, the injection port of the GC system was set in the split mode (split ratio 1:100) and 1 \(\mu\)L was injected. A purge flow of 50 mL/min was set at 2 min to avoid an oversaturation of the MS ion source.