# Repurposing Olive Oil Mill Wastewater into a Valuable Ingredi for Functional Bread Production
## 2 Materials and Methods
### Volatile Organic Compounds  
More than 60 total volatile compounds were recognized from \(B\) process breads, which constitute the aromatic component of all samples analyzed. For each sample, they were grouped by chemical class: acids, alcohols, carbonylic compounds, esters, furan compounds, terpenes, hydrocarbons, and ethers (Table 6). For each compound, the relative abundance was evaluated, a quantitative approach that has limitations, as the areas of each peak do not reflect the real quantities of the different compounds, but, these percentages are very useful as a comparison tool and provide useful indications to evaluate the contribution of OOMW in this case for bread. The volatile aromatic components of the breads were analyzed using HS-SPME-GC/MS. In the CTR\({}_{B}\) bread, 44 compounds belonging to different classes were identified, including 1 acid, 6 alcohols, 15 carboxylic compounds, 7 esters, 4 terpenes, 8 hydrocarbons, and 1 ether. Yeasts, which are crucial in bread production, facilitate the synthesis of various volatiles, such as alcohols, aldehydes, acids, esters, and ketones, through fermentation [44]. The most relevant alcohols identified were ethanol, 3-methyl-butanol, and phenylethyl  
Figure 2: Breads processed with OOMW. (**a**) \(S\) process breads, produced using exclusively sourdough as fermentation agent. Abbreviations: CTR\({}_{S}\), control production; EXP\({}_{S}\)-1, experimental 1 production (50% OOMW in substitution of water); EXP\({}_{S}\)-2, experimental 2 production (100% OOMW in substitution of water). (**b**) \(B\) process breads, produced using a biga-like fermentation agent. Abbreviations: CTR\({}_{B}\), control production; EXP\({}_{B}\)-1, experimental 1 production (50% OOMW in substitution of water); EXP\({}_{B}\)-2, experimental 2 production (100% OOMW in substitution of water). alcohol generated during fermentation or from the Maillard reaction [22]. Interestingly, 3-methyl-butanol imparts balsamic, floral, and malty notes to bread and correlates with the flavor of wheat crumb and that phenylethyl alcohol is known to have fruity, honey, lilac, and rose odors [44]. Among carbonyl compounds, hexanal, benzaldehyde, and nonal contribute to the aromatic component of the control bread and may derive from lipid oxidation. The compound 2-pentyl furan is produced through thermal reactions, such as the Maillard reaction and caramelization, which contribute to the formation of the crust and its characteristic aroma [45; 46]. Limonene is also present in the control bread sample, which is generally associated with naturally leavened bread [23]. Additionally, it is noteworthy that these samples contain several compounds absent in the control bread, suggesting they are specifically introduced by adding OOMW. Key compounds include 2-octen-1-ol, 1-octanol, 2-octanol, copaene, and farnesene. Moreover, the relative area percentages of certain compounds increased from the EXP\({}_{B}\)-1 sample to the EXP\({}_{B}\)-2 sample, indicating that the addition of OOMW had a significant impact on the volatile aroma profile of the breads. Specifically, from the EXP\({}_{B}\)-1 sample to the EXP\({}_{B}\)-2 sample, 3-methyl-butanol increased from 10.76% to 18.47%, 1-hexanol from 2.46% to 3.89%, phenylethyl alcohol from 3.60% to 4.49%, benzaldehyde from 2.74% to 3.66%, and both ethyl caproate and hexanal showed slight increases from 2.66% to 2.99% and from 0.97% to 1.08%, respectively.