## 3 Results and Discussion
### Phenolic Profiles of SWAP Materials and Fortified Wheat Breads  
Besides the determination of TPC and TFC with spectroscopic methods, the major phenolic compounds in SWAP (ORE, ROS, LEB, and SPE) extracts and fortified breads with SWAP were identified using LC/DAD/MS comparing their retention time, \(m/z\), and UV spectra with standards or/and literature data and quantified (Table 3). It is obvious that the main group of phenolic compounds in LEB- and SPE-free extracts were the phenolic acids (PAs \(>90\%\) of the total quantified phenolics), while in ROS extract, phenolic terpenids were the dominant phenolic group (PTs \(>91\%\) of the total quantified phenolics). On the other hand, in ORE-free extract, these two phenolic groups (phenolic acids and phenolic terpenids) were present at similar levels. Regarding individual phenolics, rosmarinic acid (RMA) is undoubtedly the major phenolic acid for all four SWAP-studied extracts, followed by salvianolic acid isomers (SALA, SALB, and SALI) and caffeic acid (CA). Carnacic acid (CARA) was the only phenolic terpenoid present in all four SWAP extracts, while carvacrol (CARV) was detected only in oregano waste extract and Carnosol (CARO) in rosmenary extract. Total flavonoids were found in small but similar amounts in LEB and ROS extracts, while the ORE and SPE extracts have much higher levels. Vicenin-2 (VIC) and luteolin-7-O-glucoside (LUTGL) were present in all SWAP extracts but at less than 1%, except for the ORE extract. The amount of total quantified phenolics decreased in the following order: ROS \(>\) LEB \(>\) ORE \(>\) SPE. It seemed that TPC determined spectroscopically followed a slightly different order: LEB \(>\) ROS \(>\) ORE \(>\) SPE (Figure 6a). In the case of bread samples, alkaline hydrolysis was applied in order to isolate bound phenolic compounds, as phenolic compounds form complexes with proteins via hydrogen, covalent, or ionic bonds and hydrophobic interactions [45]. Figure S1 (supplementary data) presents the chromatograms of soluble-free extracts of fortified wheat breads with ORE, ROS, LEB, and SPE post-distillation solid waste residues at 2% substitution level as well as the soluble-free and insoluble-bound (inset, Figure S1) phenolic extracts of control bread. Besides the main phenolics present in the SWAP-free extracts (Table 3), three other phenolic acids, trans- and cis-ferulic acids (t-FA and c-FA, respectively) and p-coumaric acid (pCA), were detected in both free and bound bread extracts (Figure S1 and Table 4). [PERSON] et al. [46] reported that FA and p-CA exist in the form of free acids, soluble esters, and insoluble esters in cereal grains, and therefore, these two phenolic acids and caffeic acid (CA) were the only detected phenolic compounds in the control bread (Figure S1 and Table 4). The main phenolics found in the control bread and supplemented breads with 1 and 2% SWAP are summarized in Table 4. It is evident that supplemented breads, regardless of the amount of SWAP added, have significantly higher levels of total quantified phenolics than control. Moreover, the higher the supplementation level, the higher the total phenolic compounds content; however, the baking process decreased the free total phenolics in the case of breads fortified with ORE and ROS post-distillation solid wastes (25 and 40%, respectively), compared to the theoretically expected values. On the other hand, an increase was observed in the case of breads fortified with LEB and SPE solid wastes (5 and 34%, respectively). In terms of the breadmaking process, baking decreased the content of all studied phenolic acids except for CA. In their study, [PERSON] et al. [PERSON] et al. (2017) reported that heat treatments quantitatively increased pCA, CA, and FA in brewers' spent grain. On the contrary, [PERSON] et al. (2018) reported that the roasting process adversely affects the amount of pCA in quince fruit. In another study, it was reported that autoclaving of oat grains increased pCA and FA while drastically decreasing CA ([PERSON], 2018).