Optimization of Pectin Extraction from Sweet Potato Peels Using Citric Acid and its Emulsifying Properties

Background: Pectin is a natural polysaccharide that has been used widely as a stabilizer in food emulsion system. Objective: This study aimed to optimize the yield of pectin extracted from sweet potato residue and investigate its emulsifying properties. Methods: Response surface methodology (RSM) has been utilized to investigate the pectin extracted from sweet potato peels using citric acid as the extracting solvent. Investigation of the effect of different extraction conditions namely temperature (°C), time (min) and solution pH on pectin yield (%) were conducted. A Box-Benhken design with three levels of variation was used to optimize the extraction conditions. Results: The optimal conditions determined were at temperature 76°C, time 64 min and pH 1.2 with 65.2% yield of pectin. The degree of esterification (DE) of the sweet potato pectin was determined using Fourier Transform Infrared (FTIR) Spectroscopy. The pectin is a high-methoxyl pectin with DE of 58.5%. Emulsifying properties of sweet potato pectin was investigated by measuring the zeta-potential, particle size and creaming index with addition of 0.4 and 1.0 wt % pectin to the emulsion. Conclusion: Extraction using citric acid could improve the pectin yield. Improved emulsion stability was observed with the addition of the sweet potato pectin.