Extraction and characterization of pectin from pinto bean (Phaseolus vulgaris L. var. Pinto) husk waste with hot acid and ultrasonic assisted extraction methods

In this master thesis study, extraction and characterization of pectin from pinto bean husks by hot acid extraction (HAE) and ultrasonic assisted extraction (UAE) methods were studied. The solid-liquid ratio was kept constant as 1/30 (g/mL) and extractions were carried out at different temperatures and for different times. In the study, dilute solutions of organic acids (CH₃COOH, C₆H₈O₇), inorganic acids (H2SO4, HCl) and water were used as extractants. The highest pectin yield was 29.63% with UAE and 26.05% with HAE. For the characterization of pectins, physicochemical properties such as degree of esterification (DE), methoxyl content (MeO), equivalent weight (EW), galacturonic acid (Gal-A) content were determined. FTIR and thermal analyses of some extracted pectins were performed and compared with commercial pectin. All the pectins obtained from the extractions were classified as high ester pectin. The methoxyl content of the pectins varies in parallel with their DE values. When compared with the EW value of commercial pectin, this value is higher in pectins extracted with inorganic acids and lower in pectins extracted with organic acids. Gal-A content of pectins extracted by HAE method increased with increasing temperature and time, while it decreased in pectins extracted by UAE method. The FTIR spectra and thermal behavior of the extracted pectin samples were similar to those of commercial pectin.