Cross-linking of diluted alkali-soluble pectin from apple (Malus domestica fruit) in different acid-base conditions. (July 2019)

• Record Type: Journal Article
• Authors: Gawkowska, Diana; Cieśla, Jolanta; Zdunek, Artur; Cybulska, Justyna
• Is Part Of: Food hydrocolloids. Volume 92(2019)
• Page Start: 285
• Page End: 292
• Publication Date: 2019-07
• Subjects: Pectin -- Cross-linking -- pH -- FT-IR spectroscopy -- Dynamic light scattering -- AFM nanostructure; Hydrocolloids -- Periodicals; Food additives -- Periodicals; Colloïdes -- Périodiques; Aliments -- Additifs -- Périodiques; Colloids; Food additives; Periodicals; Electronic journals; 664.06
• DOI: 10.1016/j.foodhyd.2019.02.010
• Languages: English
• ISSNs: 0268-005X

Abstract

Abstract: A diluted alkali-soluble pectin (DASP) fraction, extracted using sodium carbonate, is characterized by a low degree of methylesterification and has the ability to self-organize on mica. The aim of this study was to characterize the cross-linking process of this fraction, extracted from apples, over a wide pH range (3-11) and without the addition of salt. An FT-IR study showed an increase in the intensity of bands connected with νas and νs (COO − ) and a decrease in the intensity of the band associated with ν (C=O) in the carboxyl group with increasing pH, which indicated the dissociation of the carboxyl groups of galacturonic acid units. An increase in the surface electrical charge of particles in the pH range of 3–7 confirmed this. The value of the average apparent dissociation constant (∼4.60) indicated the acidic character of the DASP fraction. An AFM study showed the morphological changes of the DASP fraction with increasing pH, which allowed for the evaluation of the cross-linking process. This fraction formed a network on mica at pH 4 and 9, while the aggregates were noted mainly at pH 11. For totally ionized carboxyl groups (pH 7), the pectin chains were separated from each other due to the electrostatic repulsion between them. Graphical abstract: Image 10873 Highlights: Diluted alkali-soluble pectin (DASP) fraction from apples was characterized. The different acid-base conditions (pH = 3–11) were considered. The intensity changes in FT-IR bands indicated the dissociation of carboxyl groups. A surface electrical charge of particles increased in the pH range of 3–7. The DASP nanostructure was changed with increasing pH.