**2. Materials and Methods**

### *2.1. Olive Mill Waste Water Extract and Compositon*

The crude phenolic extract (PE) used in the beef burger formulation was obtained through a three-step membrane filtration process using fresh olive mill wastewaters from processing olives of the Umbrian Moraiolo cultivar, as reported by Ianni et al. [26]. To obtain a stable powder formulation, the extracts were spray-dried after their combination with maltodextrin (1:1 dw), which functioned as a carrier, and is largely used in spray drying in the food industry [27]. The phenolic composition of the spray-dried extracts was assessed by means of high-performance liquid chromatography (HPLC) [28] and is reported in Table 1.


**Table 1.** Composition of spray-dried crude phenolic extract (PE).

\* Results are the mean of two independent analytical determinations ± standard deviation. 3,4-DHPEA = hydroxytyrosol, *p*-HPEA = tyrosol, 3,4-DHPEA-EDA = oleacein.
