# Red Orange and Bitter Orange IntegroPectin: Structure and Main Functional Compounds
## 3 Results and Discussion
### DRIFT Structural Analysis
The components' centers and integrated areas are summarized in Table 2 for the two samples, as well as the values obtained for DE and to quantities proportional to HG regions. Although both pectins were extracted by the same procedure (though bitter oranges were not industrially squeezed to extract the juice), the IntegroPectin from bitter orange is an HM pectin with DE = 59%, whereas blood orange IntegroPectin is a LM pectin with DE of 32%. This outcome has known consequences in terms of applications and demand, as LM pectins tend to form gels electrostatically, in the absence of sugar and in a broad pH range (2-7), in the presence of a small amount of divalent cations such as Ca\({}^{2+}\)[20]. The outcome is another proof of the dependence of DE on the extraction method, but also on the fruit source and its processing [21]. The DE of blood orange waste IntegroPectin, in its turn, is close to that of pectin extracted from blood orange waste via microwave-assisted hydrodiffusion in water (DE = 25%) under acid-free conditions [21]. For comparison, pectin extracted from blood orange peel at pH 3 and at 100 \({}^{\circ}\)C has a high degree of methylation (>60%) and 81% galacturonic acid content [22]. This shows that the HC-based extraction acts similarly to extraction in a single-mode microwave cavity system which promotes rapid pectin de-esterification [23]. Indeed, also in the case of bitter orange, when the extraction is carried out at pH 1.5 under microwave irradiation, the bitter orange pectin obtained is an LM pectin (DE of 1.5%) [24]. The HC-based extraction, on the other hand, prevents the hydrolytic loss of the RG-I regions, particularly in the case of pectin derived from blood orange biowaste. Both pectins obtained, indeed, are rich in smooth HG regions, with bitter orange IntegroPectin having a substantially higher share of HG regions (71% vs. 63%). This points to higher quality of blood orange IntegroPectin not only because the latter is a valued LM pectin, but also because pectin molecules richer in hairy branched chains have a better and longer emulsifying activity, forming a thicker interfacial layer on the oil-water interface [25]. The structure, for example, provides stronger steric hindrance, promoting the long-term stability of the emulsion [26]. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Assignment**} & \multicolumn{2}{c}{**IP-Bitter**} & \multicolumn{2}{c}{**IP-Blood**} \\ \cline{2-5}  & **Center/cm\({}^{-1}\)** & **Area** & **Center/cm\({}^{-1}\)** & **Area** \\ \hline \(\text{v}(\text{C=O})_{\text{methyl-ester}}\) & 1749 & 3.80 & 1754 & 1.16 \\ \(\text{v}(\text{C=O})_{\text{ester}}\) & 1717 & 19.80 & 1731 & 7.09 \\ \(\text{v}(\text{C=O})_{\text{carboxylic acid}}\) & 1641 & 8.45 & 1663 & 9.25 \\ \(\text{v}_{\text{as}}(\text{COO}^{-})\) & 1592 & 8.11 & 1603 & 8.10 \\ \hline \multirow{6}{*}{v(\text{C-O-C})\({}_{\text{pyranose}}+\text{v}(\text{C-OH})+\text{v}(\text{C-C})\)} & 1138 & 2.61 & 1145 & 2.48 \\ \cline{1-1}  & 1109 & 1.77 & 1110 & 2.28 \\ \cline{1-1}  & 1081 & 3.61 & 1076 & 4.02 \\ \cline{1-1}  & 1054 & 2.49 & 1051 & 0.33 \\ \cline{1-1}  & 1020 & 4.59 & 1023 & 4.71 \\ \cline{1-1}  & 989 & 1.53 & 970 & 0.99 \\ \hline \multirow{6}{*}{v(\text{C-O-C})\({}_{\text{pyranose}}+\text{v}(\text{C-OH})+\text{v}(\text{C-C})\)} & DE & 0.59 & DE & 0.32 \\ \cline{1-1}  & HG \(\alpha\) to & 0.71 & HG \(\alpha\) to & 0.63 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Decomposition results of the 850–1800 cm\({}^{-1}\) region of the DRIFT spectra.