Extraction, structure, and emulsifying properties of pectin from potato pulp

Effects of HCl, H2SO4, HNO3, citric acid, and acetic acid on the yield, structure, and emulsifying properties of potato pectins were investigated. Results showed that the highest yield (14.34%) was obtained using citric acid, followed by HNO3 (9.83%), HCl (9.72%), H2SO4 (8.38%), and acetic acid (4.08%). The degrees of methylation (37.45%) and acetylation (15.38%), protein content (6.97%), and molecular weight (3.207 × 105 g/mol) were the highest for pectin extracted using acetic acid, and (galactose + arabinose)/rhamnose was 33.34, indicating that it had a highly branched rhamnogalacturonan I domain. Fourier transform infrared spectroscopy showed a specific absorbance peak at 1064 cm−1, which corresponds to the acetyl groups in potato pectins. SEM showed that all potato pectins are morphologically different. The emulsifying activity (EA, 44.97%–47.71%) and emulsion stability (ES, 36.54%–46.00%) of the pectins were influenced by acid types, and were higher than those of commercial citrus and apple pectin.