Multi-objective optimization of pectin extraction from orange peel via response surface methodology: yield and degree of esterification

Abstract

Pectin is extensively extracted from citrus peel for applications in food, nutrition, cosmetics and pharmaceutical industries. In this study, extraction of pectin from orange peels was attempted using different types of acid solvent, namely acetic, hydrochloric, nitric and citric acids. Fourier Transform Infrared spectroscopy revealed that distinctive functional groups of pectin were found in the extracted pectin samples using all acid solvents and the spectra were comparable to the commercial pectin reported in literature. Citric acid was identified as the best extracting solvent for the highest pectin yield (3.82%) and optimum degree of esterification (DE) (> 50%) for the extracted pectin. Multi-objective optimization of the extraction process was performed using Response Surface Methodology on the yield and degree of esterification. A five-level Central Composite Design was adopted for the experimental design involving three process variables namely extraction temperature (60–90 °C), solvent pH (2–4) and extraction time (30–90 min). The highest pectin yield at 35.20 ± 0.39% and DE of 45.43 ± 0.39% was achieved at the suggested optimum extraction conditions at 90 °C, solvent pH 2.19 and 66 min. Verification of the optimization showed that the percentage error difference between the experimental and predicted results was less than 10%, indicating significance of the established extraction model and correlation. Interestingly, the DE (< 50%) of the extracted pectin at optimal conditions revealed that low methoxyl (LM) pectin was obtained rather than high methoxyl (HM) pectin as extracted during the solvent screening process.