## 3 Results and Discussion
### Laboratory Tests  
In order to evaluate the optimal temperature to use in the pilot phase, we conducted a series of pre-screening tests at 20, 40, 55 and 87 \({}^{\circ}\)C (Table 3).  
Extraction tests were conducted using a hydroalcoholic mixture (50% V/V).  
Operating conditions:  
Temperatures: 20, 40, 55, and 87 \({}^{\circ}\)C;  
Solid/liquid ratio = 1/10;  
Extraction time: 3 h;  
At the end of the extraction, the extracts were filtered with Whitman and [PERSON] filters.  
From the data obtained in Table 3, we can draw several conclusions:  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Sample** & **gg\(\pm\)/Kgss** \\ \hline
**Fresh** & 45 \(\pm\) 2 \\
**Frozen (1a)** & 44 \(\pm\) 3 \\
**Dry (1b)** & 41 \(\pm\) 2 \\
**Frozen (2a)** & 42 \(\pm\) 5 \\
**Dry (2b)** & 40 \(\pm\) 3 \\ \hline \hline \end{tabular} Data are expressed as mean \(\pm\) standard deviation (n = 3) at \(p\) = 0.05.  
\end{table}
Table 2: Comparison of polyphenol content between dry and frozen matrix.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Parameters** & **20 \({}^{\circ}\)C** & **40 \({}^{\circ}\)C** & **55 \({}^{\circ}\)C** & **87 \({}^{\circ}\)C** \\ \hline
**pH** & 4.00 \(\pm\) 0.01 \({}^{\text{a}}\) & 4.00 \(\pm\) 0.04 \({}^{\text{a}}\) & 4.00 \(\pm\) 0.01 \({}^{\text{a}}\) & 4.00 \(\pm\) 0.04 \({}^{\text{a}}\) \\ \hline
**Dry residue \%** & 1.8 \(\pm\) 0.1 \({}^{\text{c}}\) & 1.7 \(\pm\) 0.1 \({}^{\text{c}}\) & 3.7 \(\pm\) 0.1 \({}^{\text{b}}\) & 9.1 \(\pm\) 0.1 \({}^{\text{a}}\) \\ \hline
**Total phenols** & & & & \\ **(mg/L of _A. gallic_)** & & & & \\ **(mg/L of _A. gallic_)** & & & & \\ \hline
**No flavonoid phenols** & & & & \\ **(mg/L of _A. gallic_)** & & & & \\ \hline
**Flavonoid phenols** & & & & \\ **(mg/L di _A. gallic_)** & & & & \\ \hline
**Anthocyanins** & & & & \\ **(mg/L of Malvin)** & & & & \\ \hline
**Antioxidant activity** & & & & \\ **(\(\mathbf{\mu}\)mol TEAC/mL)** & & & & \\ \hline \hline \end{tabular} Data are expressed as mean \(\pm\) standard deviation (n = 3). The letters (a,b,c,d) indicate significant differences (\(p<5\%\)) after the ANOVA analysis of variance.  
\end{table}
Table 3: pH, dry residue %, total phenols mg/L of _A. gallic_, no flavonoid phenols mg/L of _A. gallic_, flavonoids mg/L of _A. gallic_, anthocyanins mg/L of Malvin, and antioxidant activity \(\mathbf{\mu}\)mol TEAC/mL of extract of the pomace extracts obtained using temperatures of 20, 40, 55, and 87 \({}^{\circ}\)C.  
The pH in the various extractions carried out at the indicated temperatures is approximately 4, a value that does not allow the conservation of the extracts in liquid form, which, having a high water activity, could be altered by the development of unwanted bacteria. Therefore, if one did not want to proceed with the drying process of the extracts (the possible industrial production of extracts in aqueous solution), it would be necessary to use acidifiers such as citric acid (E330) and lactic acid (E270).  
At higher temperatures, a higher dry residue is obtained, a higher quantity of phenols (flavonoids and otherwise), and a greater antioxidant activity of the extracts, also given the use of an inert atmosphere (N\({}_{2}\) 100%): in these conditions, the increase in the extraction of the analysed compounds is decidedly greater than any thermal degradation of the same.  
Based on the results obtained in the laboratory, we subsequently continued with pilot-scale studies. We conducted three phenolic compound extraction tests, exploiting all the variables developed in the previous phase.