Ultrasound-assisted extraction of pectin from Spondias purpurea L. peels residues: optimization, characterization, and comparison with commercial pectin

This study investigated the extraction of pectin from the byproduct of Spondias purpurea L. peels using the ultrasound-assisted extraction (UAE) technique. The extraction process was optimised using the Box-Behnken design (BBD), resulting in a maximum yield of 24.2% under ideal conditions of temperature at 70 degrees C, power at level 4, and pH 1.9, after 35 min of sonication, as validated by the experimental results (25.09 +/- 0.12%). Both commercial pectin (CP) and UAE pectin exhibited high esterification, with a degree of esterification of 51.10 +/- 0.24% and 53.19 +/- 0.71% (p = 0.072), respectively. Methoxyl contents were determined as 7.01 +/- 0.03% for CP and 7.23 +/- 0.19% (p = 0.092) for UAE. Additionally, UAE demonstrated high antioxidant capacity (p = 0.059) as well as water/oil holding capacity (p = 0.058; p = 0.051) and emulsification properties similar to those of CP. X-ray diffraction (XRD) patterns indicated greater crystallinity in the pectin obtained by ultrasound compared to commercial pectin. Scanning electron microscopy (SEM) revealed a smoother surface on the ultrasound-obtained pectin than on commercial pectin. Fourier transform infrared (FT-IR) spectroscopy confirmed the presence of galacturonic acid units in both samples. Thermal analysis by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) revealed greater thermal stability in the pectin obtained by ultrasound compared the commercial pectin. A detailed comparative study on the properties of pectin extracted by ultrasound from Spondias purpurea L. peels and commercial pectin confirmed the quality of the extracted pectin, indicating its potential use as a food ingredient in the food industry.