Interaction of sugar beet pectin and pea protein: Impact of neutral sugar side chains and acetyl groups

Sugar beet pectin (SBP) is becoming increasingly interesting due to its complex molecular structure and emulsifying properties. Compared to citrus pectin, SBP differs, for example, in the content of neutral sugar side chains and acetyl groups. In this study it was assumed that side chains lead to steric hindrance between SBP and pea protein and the electrostatic interactions are reduced. Therefore, the aim of the present study was to investigate the impact of the neutral sugar side chains of SBP on steric hindrances and the impact of the acetyl groups on the interaction with pea protein. The interaction of four SBP samples varying in the content of neutral sugar side chains and three SBP samples differing in degree of acetylation with soluble pea protein fractions were investigated. Electrostatic interaction between SBP and protein was qualitatively tested via turbidity measurements and the results were presented in state diagrams. Quantitative evaluation of the interactions was obtained by isothermal titration calorimetry (ITC). The highest interaction was obtained for both SBP sample sets by a protein-to-pectin ratio of 4:1. Less content of neutral sugars resulted in enhanced maximum turbidity. This was confirmed by the ITC measurement, where more possible binding sites and a higher binding affinity was observed. A higher content of acetyl groups increased the interaction with the pea protein, which was supported by the turbidity and ITC measurement. These effects need to be considered when using SBP for designing new systems with plant-based proteins in the food and pharmaceutical industry. [Display omitted] •Protein-pectin interactions were enhanced in case of less neutral sugar side chains.•Less side chains resulted in more binding sites and a higher binding affinity.•Protein-pectin interactions were increased with a higher degree of acetylation (DAc).•Pectin with higher DAc shows more binding sites and higher binding affinity.