Spectroscopic and Microscopic Analysis of Apple Pectins
Agata Serrafi, Agnieszka Wikiera, Konrad Cyprych, Magdalena Malik
Abstract
Apple pomace pectins, extracted using various methods (water, cellulase, arabinase, and arabinase with mannanase), and commercial apple pectin were studied, analyzing their morphology and chemical structure. The microscopic analysis revealed morphological differences, with a log-normal particle size distribution observed in most samples, except for those extracted with water. Cellulase-extracted pectin exhibited the most spherical morphology, while enzymatically extracted pectins displayed uneven surfaces. The FT-IR analysis indicated structural changes, shifts in O-H bands, and the degree of methoxylation (DM) ranged from 30.25% to 58%, with all the pectins classified as high-methoxy pectins. The NMR (1H and 13C) analysis confirmed the presence of arabinans, galactans, galacturonans, and rhamnose, and the calculated DM and acetylation (DAc) values were consistent with the results obtained using conventional methods. These results provide insight into the influence of extraction methods on pectin properties, which is relevant to the pharmaceutical and food industries, and confirm the structural similarity between enzymatically extracted pectins and commercial pectin.