Extraction and characterization of pectin from carambola (Averrhoa carambola) peel using conventional, microwave-assisted and ultrasound-assisted techniques

This study aimed to extract and characterize pectin from carambola (Averrhoa carambola) peel using three extraction techniques: conventional acid extraction (CAE), microwave-assisted extraction (MAE), and ultrasound-assisted extraction (UAE). Pectin was extracted using organic citric acid at pH 2, and the study comprehensively evaluated its yield and solubility along with physicochemical properties—equivalent weight (EW), methoxyl (MeO) content, anhydrouronic acid (AUA) content, degree of esterification (DE), ash percentage, and pH—across the three extraction methods. The results revealed that the extraction technique significantly impacted the yield and properties of pectin. Among the methods, MAE produced the highest yield of pectin (22.38 ± 0.32 %), demonstrating its efficiency. Each extraction method offered distinct advantages, influencing both the physicochemical characteristics and solubility behavior of the pectin. Based on the MeO and DE values, all extracted pectins from carambola peel were identified as high-methoxyl pectins, making them suitable for various industrial applications. Additionally, the high AUA content indicated the purity of the extracted pectin. Fourier transform infrared (FTIR) spectroscopy was employed to distinguish the extracted pectin structurally. The spectral analysis identified functional groups within the 1800–800 cm−1 range, confirming the presence of key chemical components associated with pectin’s structure. This study highlights the comparative advantages of MAE and UAE in enhancing pectin yield and purity while preserving its functional properties. These findings underscore the potential of carambola peel-derived pectin for applying in gel formation, stabilization, emulsification, and thickening of food products.