## 3 Results and Discussion
### Chromatography and Mass Spectrometry of ISP Extracts  
The RP-HPLC chromatograms of samples of brine and meat ISP extracts are presented in Figure 1 in the main text, and in Figures S1-S6 in the Supplementary Materials. Figure 1 presents chromatograms within the time interval up to 60 min. Chromatograms presented in this figure show peaks with retention times between 15 and 60 min. Entire chromatograms are presented in the Supplementary Materials (Figures S1-S6). Our resignation from the interpretation of the injection peaks may appear controversial, due to the fact that short and hydrophilic peptides may be not retained at the column, but on the other hand, absorbance at the injection peak apex is c.a. 4, and is too high to provide predictable dependence between the composition of the solution and the output from the detector. The peaks at the start of the chromatogram contain many low-molecular compounds belonging to various classes. It is impossible to estimate the contribution of peptides in this fraction. In our previous works [27; 28; 29], interpretation of the area of injection peaks did not provide valuable information, in contrast to fractions with retention times exceeding 15 min. A time interval exceeding 60 min contains so-called system peaks, artifacts that are useless from the point of view of information about the sample [30]. The sample concentration of the meat extracts was three times higher than the concentration of the brine samples. The retention times of peptides depend on their hydrophobicity and length. More hydrophobic and longer chains have longer retention times than those that are shorter and more hydrophilic. Reversed-phase HPLC does not provide a simple correlation between retention time and molecular mass [31; 32], but experiments using proteins from herring [33] and other sources [27; 28; 34; 35; 36; 37] may serve as examples, illustrating the fact that retention times of proteolysis products are usually shorter than those of entire proteins. Thus, RP-HPLC \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Analyses**} & \multicolumn{3}{c}{**Marinating Temperature**} \\ \cline{2-4}  & 2 \({}^{\circ}\)C & 7 \({}^{\circ}\)C & 12 \({}^{\circ}\)C \\ \hline Appearance & 4.95 \(\pm\) 0.09 \({}^{\mathrm{a}}\) & 4.91 \(\pm\) 0.10 \({}^{\mathrm{a}}\) & 4.79 \(\pm\) 0.23 \({}^{\mathrm{a}}\) \\ Color & 4.60 \(\pm\) 0.51 \({}^{\mathrm{a}}\) & 4.65 \(\pm\) 0.41 \({}^{\mathrm{a}}\) & 4.79 \(\pm\) 0.25 \({}^{\mathrm{a}}\) \\ Flavor & 4.30 \(\pm\) 0.42 \({}^{\mathrm{a}}\) & 4.39 \(\pm\) 0.53 \({}^{\mathrm{a}}\) & 4.78 \(\pm\) 0.23 \({}^{\mathrm{a}}\) \\ Texture & 4.37 \(\pm\) 0.35 \({}^{\mathrm{b}}\) & 4.42 \(\pm\) 0.23 \({}^{\mathrm{b}}\) & 4.91 \(\pm\) 0.07 \({}^{\mathrm{a}}\) \\ Overall sensory & 4.45 \(\pm\) 0.40 \({}^{\mathrm{a}}\) & 4.51 \(\pm\) 0.37 \({}^{\mathrm{a}}\) & 4.84 \(\pm\) 0.17 \({}^{\mathrm{a}}\) \\ \multicolumn{4}{c}{} \\ TPA hardness & 10.49 \(\pm\) 0.95 \({}^{\mathrm{a}}\) & 8.03 \(\pm\) 0.57 \({}^{\mathrm{b}}\) & 7.40 \(\pm\) 1.14 \({}^{\mathrm{b}}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Sensory assessment and TPA hardness of marinated meat; \({}^{\mathrm{ab}}\) means within the same row with different lowercase letters differing significantly. may serve as a tool for the comparison of the proteolysis degree if it is not determined directly. Chromatograms of samples with an unknown composition may be subjected to simple interpretation by comparison of the relative area of peaks within various retention time intervals [27; 28; 29]. The relative areas of peaks within the intervals 15-34.99 min (shorter) and 35-60 min (longer) are presented in Table 4. It is possible to discriminate the chromatographic patterns of the brine and meat extracts. The brine extracts contain more material within a shorter retention time interval, compared with the meat extracts. This suggests the predominant extraction of hydrophilic or short peptides during marinating.