Influence of structure of the diluted alkali soluble pectin (DASP) fraction on physical stability of emulsion

PRELUDIUM 22

Funding Organization: National Science Centre

Project title: Influence of structure of the diluted alkali soluble pectin (DASP) fraction on physical stability of emulsion

Agreement number: UMO-2023/49/N/NZ9/01701

Project implementation period: 01.02.2024 - 31.01.2027

Principal Investigator: dr Adrianna Kaczmarska-Król

Project value: 209 840,00 PLN

Funds granted for Lublin University of Technology: 121 920,42 PLN

Abstract: The goal of this research is to identify influence of structure of the diluted alkali soluble pectin (DASP) on physical stability on pectin-containing emulsions.

Diluted alkali soluble pectin fraction, extracted by sodium carbonate is obtained after depleting water and calcium chelator soluble pectins from cell walls. DASP is then considered as the pectin covalently linked in cell wall and is extracted with the highest efficiency of all fractions by sequential extraction. DASP has been the subject of research due to its characteristic self-assembled network on mica, which disintegrated during postharvest ripening (Cybulska et al., 2015). Extensive analysis were conducted on molecular structure of DASP using atomic force microscopy as well as molecular dynamics simulations (P. M. Pieczywek et al., 2020). Modeling studies confirmed that rhamnose interspersions create kinks (c.a. 118°) in linear homogalacturonan (Rees & Wight, 1971). The kinks may affect the cross-linking properties of DASP, and thus the gelling properties, as the greater mobility of linear segments allows for an increase in the degree of interaction with other molecules.

Recent studies in my doctoral thesis, suggested that removal of rhamnose units with simultaneous deacetylation and removal of arabinose side chains in DASP solution resulted in obtaining similar rheological parameters for two plant sources with initially different properties (not published yet). The selective degradation of arabinose side chains, caused significant decrease in elastic properties of DASP solution. The described changes were coupled with changes in the structure of molecules on the mica observed by the AFM. It is suspected that arabinose is involved in the formation of the pectin network, affecting the pseudoplastic properties and viscosity, but does not affect the mechanical strength in pectin solutions and rhamnose is one of the factors influencing the properties of pectin matrix in solution (Project no. 2019/35/O/NZ9/01387 Preludium BIS1 headed by prof. Artur Zdunek in which I am PhD student). Recently, more attention is given to the emulsifying and emulsion-stabilizing properties of pectin, which is closely related with evaluation of the specific structural features of pectin on their functions. Stability of emulsion systems is closely related to the preparation method, emulsifier type and concentration, temperature, and pH of the media. Identification of physical and/or chemical mechanisms responsible for the emulsion instability is crucial for design the most effective technique to improve its stability. Pectin gelling capacity and viscous properties can be used to improve the stability of emulsions It has been shown that polysaccharides in O/W emulsions increase the viscosity of the aqueous phase, as well as the spatial repulsive force and electrostatic repulsion between the oil droplets, being effective in the preparation of emulsions and improving of their rheological properties

In this project it is hypothesized that in DASP fraction, the rhamnose units with attached arabinose and galactose side chains, forming interspersions in the linear HG may influence emulsion formation and/or emulsion-stabilizing properties.

An approach of this study is to use  specific enzymes that modify the backbone and side chains of DASP fraction polysaccharides. This will allow for precise control of the occurrence of selected structural elements within a fraction and determination of influence of particular saccharides of emulsifying and emulsion-stabilizing properties. Apples, widely used in the juice industry and being a waste product, will be used as the source of pectin. The properties of the DASP-stabilized emulsions in relation to their structural characteristics will be assessed through an experimental approach involving the determination of a range of physicochemical and emulsifying properties as well as the physical stability of the emulsions.