## 2 Results and Discussion  
### Total Phenolic Content  
BE apples are highly heterogeneous materials, composed of well-balanced macronutrients (mainly proteins and carbohydrates), micronutrients (minerals and vitamins) and phytochemicals, such as phenolic acids, flavonoids and dihydrochalcone. In Table 1 are presented the results of the TPC from the BE apple extracts, and concentrations varied between 2.82 \(\pm\) 0.21 and 4.64 \(\pm\) 0.64 mg GAE/g of DE depending on the extraction methodology. The extracts with the highest TPC were obtained in CET (4.64 \(\pm\) 0.64 mg GAE/g of DE) and MAE (4.44 \(\pm\) 0.32 mg GAE/g of DE) without statistically significant differences (_p_ > 0.05) followed by CE (2.95 \(\pm\) 0.31 mg GAE/g of DE) and UAE (2.82 \(\pm\) 0.21 mg GAE/g of DE) (_p_ > 0.05). The methodologies with higher temperature extraction (CET and MAE) were shown to generate BE apple extracts with higher TPC values, while CE and UAE showed the lowest values. Since the extracting solvent, solvent/sample ratio and moisture content in the fruit were the same, it can be concluded that the high temperature reached in MAE and CET (80 \({}^{\circ}\)C) was responsible for the highest values of TPC. The temperature might soften the fruit tissue and weaken the polyphenols-protein and polyphenols-polyacrylamide interaction, leading to disruption and consequent migration of phenolic compounds to the solvent [21]. Similarly, several works with apple pomace and other fruits have confirmed that the use of high temperatures promotes an increase of the solute solubility in the solvent, leading to a higher mass transfer rate and, consequently, higher content of polyphenols [21; 22]. For instance, [PERSON], et al. [23] found that CET with 50% of ethanol at 80 \({}^{\circ}\)C, with a solvent/sample ratio 100 mL/g, provided the extract from Red Delicious waste peels with higher TPC than CE. However, the heating created in MAE has been reported to present higher advantages than CET since the process of energy transmission allowed to get homogeneous heating of the sample, shorter extraction time and lower power energy to perform the extraction [24]. Indeed, the study carried out by [PERSON], et al. [25] demonstrated that MAE provided higher TPC than CE (reflux without temperature), and then UAE. Several studies report that UAE was developed to improve the yield of phenolic compounds extraction and other \begin{table}
\begin{tabular}{c c} \hline \hline
**BE Apple** & **TPC** \\
**Extracts** & **(mg GAE/g DE)** \\ \hline CE & 2.95 \(\pm\) 0.31 \({}^{\mathrm{b}}\) \\ CET & 4.64 \(\pm\) 0.64 \({}^{\mathrm{a}}\) \\ MAE & 4.44 \(\pm\) 0.32 \({}^{\mathrm{a}}\) \\ UAE & 2.82 \(\pm\) 0.21 \({}^{\mathrm{b}}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The Total Phenolic Content (TPC) in \({}^{\mathrm{}}\)Bravo de Esmolfe’ apple extracts. Values are represented by the average \(\pm\) standard deviation. Different letters in row (a, b) mean significant differences between extraction methodologies, determined by [PERSON]’s test (_p_ < 0.05). bioactive compounds compared to CE methods [26], including studies with apples and apple by-products report the UAE extracted higher TPC than in CE [26; 27]. For instance, [PERSON] et al. [28] obtained an aqueous extract with ultrasonic bath from Red Delicious apples with great polyphenols content (16.36 mg/g dry weight) comparing to CE. The enhancement of UAE is due to the intensification of mass transfer and solvent penetration into the solute, as well as cell disruption due to the cavitation process, while the MAE allows rapid, efficient and homogeneous heating, which also results in the expansion and rupture of cell walls and increased solvent penetration. However, in this study, the TPC values obtained in the extract from UAE were not statistically different (\(p>0.05\)) from the CE. The reason for the absence of differences could be related to the fact that, in this study, indirect UAE was used to proceed with extraction, i.e., an ultrasonic bath was used (Figure 4).