## 3 Results and Discussion
### Spent Coffee Ground Characterization
Chlorogenic as well as neochlorogenic acids were identified with the use of the respective pure compounds as internal standards. It can be observed that water extracted the majority of CQAs, while the MeOH:H\({}_{2}\)O mixture recovered mainly the residuals of CQAs from the water extraction. The methanol-water mixture additionally extracted 3 CQAs with retention times of 32.8, 33.9, and 36.8 min, and the water either recovered them as traces (former two) or did not extract them at all (CQA, with a retention time of 36.8 min). The peaks that presented the characteristic spectrum of chlorogenic acid (3-CQA) (Figure 1) were summed, and their concentration in each extract was calculated according to the calibration curve of 3-CQA. The recovery of chlorogenic acids by the successive H\({}_{2}\)O and MeOH:H\({}_{2}\)O extractions was determined at 6.5 \(\pm\) 0.4 and 0.98 \(\pm\) 0.07 mg/gdry SCG, respectively. Chlorogenic and neochlorogenic acids were the most abundant CQAs, presenting concentrations of 2.43 \(\pm\) 0.06 and 1.00 \(\pm\) 0.04 mg/gdry SCG, or 37.3% and 15.4% of total CQAs, taking into consideration both higher polarity extracts. In general, the micromolecular phenolic components of SCG were recovered by the polar solvents, and \begin{table}
\begin{tabular}{l c} \hline
**Contents of Dried SCG** & **Concentration** \\ \hline Total Phenolic Content (mg GAE, 1 per g dry SCG) & 21.6 \(\pm\) 0.7 \\ Recovered by H\({}_{2}\)O & 11.0 \(\pm\) 0.6 \\ Recovered by MeOH:H\({}_{2}\)O (1:1) & 5.0 \(\pm\) 0.2 \\ Recovered by acetone:H\({}_{2}\)O (1:1) & 2.2 \(\pm\) 0.1 \\ Recovered by acetone & 3.3 \(\pm\) 0.1 \\ Oil Content (\% on dry SCG) & 12.2 \(\pm\) 0.5 \\ Total Dietary Fiber (\% on dry SCG) & 66 \(\pm\) 5 \\ Total Kjeldahl Nitrogen (\% on dry SCG) & 2.0 \(\pm\) 0.1 \\ Ash (\% on dry SCG) & 2.0 \(\pm\) 0.1 \\ \hline \end{tabular} 1  
\end{table} 
Table 2: Total Phenolic Content, oil content, and Total Dietary Fiber of dried SCG. the mixture MeOH:H\({}_{2}\)O was characterized as the most efficient since it not only extracted the residual phenolics that water could not recover but also the 3 lower polarity CQAs that were in traces or absent from water extract. The following acetone-water and pure acetone extractions did not recover any CQAs (chromatograms not shown) or flavonoids, but at the same time, they possessed 25.6% of the TPC content of SCG. [PERSON] et al. (2019) [PERSON] et al. (2019) identified a- and b-tocopherols in the acetone extract of defatted SCG. The compounds consisted of low-polarity phenolics reactive to the Folin-Ciocalteu reagent. The totaltocopherol content of SCG has been determined by [PERSON] et al. at 193.5 \(\mathrm{\SIUnitSymbolMicro g}/\mathrm{g}_{\mathrm{SCG}}\)[PERSON] et al. (2019). In the current research, the lower polarity extracts presented TPC in total of 5.5 mg GAE/g\({}_{\mathrm{dry\,SCG}}\), almost 30-fold higher than the expected tocopherols. Therefore, TPC values cannot be justified only by tocopherols. The chromatograms of acetone-water and acetone extracts were examined thoroughly for the detection of tocopherols, but no relevant UV spectra were identified. This contradiction could be attributed to non-phenolic compounds that react with the Folin-Ciocalteu reagent, as mentioned above. The low polarity content of SCG exhibits a high yield, up to 11%, according to the fractionation experiments presented in Table 2, a fact that could render coffee oil an exploitable material for future studies. It has been reported that the application of Soxhlet extraction with seven different (polar or non-polar) solvents on SCG at a range of temperatures (boiling point: 60-111 \({}^{\circ}\)C) yielded 9% to 15% oil content per dry base [PERSON] et al. (2019). Furthermore, the low-polarity material could present a severe sensory impact after the incorporation of SCG in cookies. Therefore, it was decided to remove the coffee oil material prior to the addition of SCG to the cookie dough. In the present study, SCG oil removal was carried out with hexane extraction at ambient temperature.