## 3 Results and Discussion
### Comparison of MW-HPCO\({}_{2}\) and CE Methods
\begin{table}
\begin{tabular}{l l l} \hline \hline
**Sample** & **CE-GPP** & **MW-HPCO2-GPP** \\ \hline Yield (\%) & 24.74 \(\pm\) 0.07 \({}^{\text{a}}\) & 27.69 \(\pm\) 0.07 \({}^{\text{b}}\) \\ GaIA (\%) & 73.79 \(\pm\) 0.23 \({}^{\text{a}}\) & 83.90 \(\pm\) 0.06 \({}^{\text{b}}\) \\ DE (\%) & 69.30 \(\pm\) 0.92 \({}^{\text{a}}\) & 71.76 \(\pm\) 0.81 \({}^{\text{b}}\) \\ Eq.W & 2383.8 \(\pm\) 2.19 \({}^{\text{a}}\) & 5049 \(\pm\) 1.41 \({}^{\text{b}}\) \\ Methoxyl content (\%) & 8.93 \(\pm\) 0.05 \({}^{\text{a}}\) & 10.44 \(\pm\) 0.08 \({}^{\text{b}}\) \\ Reducing sugar (\%) & 8.43 \(\pm\) 0.23 \({}^{\text{a}}\) & 7.68 \(\pm\) 0.22 \({}^{\text{b}}\) \\ Color & & \\ L* & 74.69 \(\pm\) 0.35 \({}^{\text{a}}\) & 90.68 \(\pm\) 0.22 \({}^{\text{b}}\) \\ a* & 1.43 \(\pm\) 0.09 \({}^{\text{a}}\) & 1.42 \(\pm\) 0.11 \({}^{\text{a}}\) \\ b* & 23.36 \(\pm\) 0.49 \({}^{\text{a}}\) & 21.10 \(\pm\) 0.10 \({}^{\text{b}}\) \\ Viscosity (mPa.s) & 16.67 \(\pm\) 0.43 \({}^{\text{a}}\) & 31.37 \(\pm\) 0.63 \({}^{\text{b}}\) \\ \hline \hline \end{tabular}  
* CE-GPP: grapefruit peel pectin obtained by conventional extraction; MW-HPCO\({}_{2}\)-GPP: grapefruit peel pectin obtained by MW-HPCO\({}_{2}\); GaIA: galacturonic acid; DE: degree of esterification; Eq.W: equivalent weight. Data are presented as mean \(\pm\) standard deviation. Different superscript letters in the same row differ significantly (\(p\) < 0.05).  
\end{table} 
Table 3: Physicochemical properties of extracted GPP samples. peel pectin had higher DE values than conventionally extracted pectin. DE is a significant factor for the gelation and emulsion capacity of pectin [35]. [PERSON] et al. [36] stated that pea pectin with high DE showed greater interactions than pectin with lower DE, and that the emulsifying properties of citrus pectins at different DE also changed. DE values of GPP obtained by both methods are greater than 50% and can be classified as HMP. Additionally, it has the facility to form a fast-setting gel with DE > 70%. According to the GalA and DE results, the MW-HPCO\({}_{2}\)-GPP can be used commercially in food applications in which high methoxyl pectin is required. The exact number of unesterified free galacturonic acid in the pectin chains is equal to the equivalent weight of pectin, and a high value of equivalent mass for pectin is a good indicator of gel formation [37; 38]. MW-HPCO\({}_{2}\)-GPP had significantly higher (\(p\) < 0.05) equivalent weight compared to CE-GPP (Table 3). It may be due to less pectin degradation in the MW-HPCO\({}_{2}\) method. Similarly, [PERSON] and [PERSON] [26] reported that equivalent weight of pectin achieved by microwave-assisted extraction was higher than that obtained by the traditional extraction method due to more pectin degradation in the traditional method. The methoxyl percentage of pectin shows the number of methyl ester clusters on its structure and is an important factor determining its gel-forming ability, sensitivity to polyvalent cations, and setting time. It also represents the ability of pectin to disperse in water. The methoxyl percentage of MW-HPCO\({}_{2}\)-GPP was significantly higher (\(p\) < 0.05) than that of CE-GPP (Table 3). The methoxyl percentage of GPP obtained by both extraction techniques was higher than 7. This indicates that pectins obtained in this study are classified as high-methyl pectin (commercially 8-11% methoxyl content) [34; 39]. Methoxyl contents greater than 7% indicate that pectin can form gels at high sugar concentration (>65% sugar). Therefore, the GPP obtained in the current study is easily dispersed in water, has high sugar-binding capacity, and may be suitable for the preparation of products such as jam and jelly, because products with high acidity and high sucrose concentration (>65%) require high methoxyl pectin [38]. Pectin monosaccharides are linked together by glycosidic bonds. The breakdown of these linkages leads to an increase in the reducing sugar content of pectin [40].