Utilization of Bitter Orange Seed as a Novel Pectin Source: Compositional and Rheological Characterization

The seeds from bitter orange, the by-product of juice making units, hold the potential to facilitate novel, easy yet high-quality pectin extraction. To test this hypothesis, orange seed pectin (OSP) was extracted by distilled water and its compositional parameters and rheological behavior were then evaluated. Results showed that galacturonic acid was the major component of OSP (∼425 mg/g) confirming the purity of the extracted pectin, followed by glucose and some minor neutral sugars. The Mw (weight-average molar mass), Rn (number average molar mass), and Rz (z-average molar mass) values for the OSP were 4511.8 kDa, 61 nm, and 61.1 nm, respectively. Rheological measurements showed a shear-thinning behavior for OSP so that the viscosity of the gum decreased by increasing the temperature from 5 to 45°C. The Power-law model fitted as the best rheological model describing the flow behavior of OSP. The strain sweep dynamic rheological measurements confirmed an entangled network structure for OSP and the NaCl addition to the gum dispersion decreased the consistency coefficient from 35.6 to 23.18 Pa.sⁿ, while the flow behavior index remained unchanged. These results demonstrate that the OSP can be used as a new source of pectin, with likely a wide range of applications in the food industry.