## 3 Results
### Identification of Peptides Likely to Be Bitter Derived from SPC Hydrolysates
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Protein Source** & **Parent Peptide** & **m/z** & **t\({}_{\text{R predicted}}\) (min)** & **t\({}_{\text{R experimental}}\) (min)** & **Motif 1** \\ \hline \multicolumn{6}{c}{B-SPC 2 **} \\ \hline glycinin & \begin{tabular}{c} LSVISPK \\ DVLVIPLG \\ \end{tabular} & 743.466 & 25.430 & 22.580 & **PK**, **VI** \\  & \begin{tabular}{c} DVLVIPLG \\ \end{tabular} & 825.509 & 43.140 & 39.540 & **VL**, **VI**, **LG**, LV 3  \\ \hline \(\beta\)-conglycinin & \
\begin{tabular}{c} LIVILNG \\ NPFLFG \\ \end{tabular} & 741.487 & 38.280 & 39.390 & **VI**, **IV**, **LI**, **IL** \\  &
\begin{tabular}{c} NPFLFG \\ \end{tabular} & 694.356 & 41.170 & 39.860 & FG, **FL**, **LF**, **PF** \\ \hline \multicolumn{6}{c}{F-SPC} \\ \hline
7S globulin & \begin{tabular}{c} ISSTIV \\ glycinin \\ \end{tabular} & \begin{tabular}{c} 619.367 \\ PQMIV \\ \end{tabular} & 700.407 & 34.500 & 40.620 & **II**, **IV** \\ \hline \(\beta\)-conglycinin & \begin{tabular}{c} PFPSIL \\ (\(\beta\)-chain) \\ \end{tabular} & \begin{tabular}{c} 673.392 \\ DDFFL \\ \end{tabular} & 656.293 & 41.170 & 34.782 & **FF**, **FL** \\  & \begin{tabular}{c} **FFE**ITPEK \\ \end{tabular} & 1010.520 & 35.950 & 36.200 & **FF**, **EI** \\ \hline \multicolumn{6}{c}{P-SPC} \\ \hline \(\beta\)-conglycinin & \
\begin{tabular}{c} LIVILNG \\ (\(\alpha\)-chain) \\ \end{tabular} &
\begin{tabular}{c} 741.487 \\ \end{tabular} & 38.280 & 39.390 & **VI**, **IV**, **LI**, **IL** \\ \hline \hline \multicolumn{6}{c}{\({}^{1}\) Bitter-tasting indicators are given in bold; 2 B-SPC, F-SPC, and P-SPC: bromelain-, fcin-, and papain-soybean protein hydrolysate, respectively (see the Materials and Methods); 3 peptides with no indicator status are given in normal font.[ENDFOOTNOTE]**} \\ \end{tabular}
\end{table} 
Table 3: Parent peptides identified in SPC hydrolysates using LC-MS/MS (Reversed-Phase High Performance Liquid Chromatography online with tandem Mass Spectrometry). One peptide, i.e., DD**FFL**, with two encrypted indicators: **FF** and **FL**, was identified in F-SPC. It matched the \(\beta\)-chain of \(\beta\)-congplycinin. The most intensive peak eluted for about 35 min (see Figure 3); however, the theoretical retention time calculated for this peptide was 41.170 min. The difference between \(\mathrm{t_{R}}\) predicted and \(\mathrm{t_{R}}\) experimental exceeded the threshold value of 10% for defining the peptide as identified [21]. The m/z of the (M+H)\({}^{+}\) precursor ion of the DD**FFL** peptide was 656.300 Da, and nine intensive peaks were observed in 35 min. They were the following fragment ions: \(\mathrm{X_{2}}^{+}\), \(\mathrm{C_{4}}^{+}\), \(\mathrm{B_{4}}^{+}\), \(\mathrm{B_{3}}^{+}\), \(\mathrm{B_{2}}^{+}\), \(\mathrm{A_{3}}^{+}\), \(\mathrm{A_{5}}^{+}\), \(\mathrm{Z_{2}}^{+}\), and \(\mathrm{Z_{4}}^{+}\). All of them occurred in thousands of counts. Thus, the DD**FFL** peptide was considered as identified in the F-SPC sample. Some differences between predicted and experimental RT (retention time) were observed during the microLC-ToF-MS (i.e., micro liquid chromatography time-of-flight mass spectrometry) identification of bioactive peptides derived from yoghurt. According to [PERSON] et al. [26], such an unequivocal identification based on retention time differences is called Type 1 identity conflict. Figure 2: LC-MS/MS (Reversed-Phase High Performance Liquid Chromatography online with tandem Mass Spectrometry) chromatograms of total ion current (upper chromatogram: 1010.5 \(>\) 272:1021 Da) and daughter ions of the **FFE**ITPEK peptide matching the \(\beta\)-congplycinin (\(\beta\)-chain) fragment, identified among products of the soybean protein concentrate hydrolyzed by ficin. Nomenclature of daughter ions according to [PERSON] and Fohlman [25]. It is well documented in the literature that some biopeptides impart bitter taste, which is a limitation when thinking about their implementation in foods supporting the prophylaxis of diet-related diseases [27]. This especially concerns ACE-inhibiting peptides [28].