Partial Restriction. Restriction lift date: 2029-12-31
The formation and physiochemical properties of Tremella fuciformis polysaccharide-proteins complex
Loading...
Files
Date
2024
Authors
Tian, Lili
Journal Title
Journal ISSN
Volume Title
Publisher
University College Cork
Published Version
Abstract
Protein-polysaccharide electrostatic interactions have received increasing research interest during the last two decades due to their potential applications in food systems. The nature of protein-polysaccharide interactions varies depending on biopolymer characteristics and environmental conditions. However, the effects of internal and external factors on protein-polysaccharide interactions and complex formation have not been thoroughly studied. This study compares the electrostatic interactions of different protein-polysaccharide systems under varying solution pH levels, biopolymer concentrations, and biopolymer ratios. Additionally, the impact of physical treatments on these interactions and the resulting physicochemical properties of the protein-polysaccharide complexes are investigated.
Tremella fuciformis polysaccharide (TPS) was extracted and characterized for its chemical composition and functional properties. As an anionic polysaccharide, TPS exhibited a high viscosity and strong emulsion-stabilizing ability. The interaction between TPS and whey protein isolate (WPI) at a biopolymer concentration of 0.1% was strongest at pH 3.2 with a WPI/TPS ratio of 2:1. Compared to gum Arabic (GA), TPS showed a stronger affinity to WPI with more binding sites. When WPI was compared to lentil protein isolate (LPI) and soy protein isolate (SPI), both similarities and differences were observed in their complex coacervation with TPS and in the characteristics of emulsions stabilized by these protein-TPS complexes. The turbidity curves showed that the onset pH of soluble complex formation remained unchanged for all protein-TPS systems, and the onset pH of insoluble complex formation shifted to higher values with increasing protein/TPS ratios; the pH at which the maximum amount of insoluble WPI:TPS and SPI:TPS complexes formed shifted to higher values with increasing protein/TPS ratios, a shift that was not observed for the LPI:TPS system, likely due to the lower solubility of LPI. The main components of each protein interacting with TPS have been identified. Different proteins exhibited distinct changes in secondary structure when interacting with TPS. At pH 4.5, a high ratio of TPS increased the stability of protein emulsion, regardless of protein type. However, WPI:TPS emulsions with low TPS ratios were extremely destabilized due to the formation of insoluble WPI:TPS complex coacervates, a phenomenon not observed in the emulsions stabilized by LPI:TPS and SPI:TPS groups.
To address LPI’s low solubility, the ultrasound treatment (UT) was applied. The interaction between sonicated LPI and TPS was studied. As the duration of sonication increased, the sonicated LPI samples exhibited decreased intrinsic fluorescence, higher zeta potential values, and increased solubility. The pH at which the maximum amount of insoluble LPI:TPS complexes formed shifted to higher values as the LPI solubility improved. The longest ultrasound treatment (40 min) resulted in the strongest binding affinity of LPI with TPS, corresponding with the highest viscosity observed in their mixture solution as the amount of complex formation increased. The effect of UT on the physicochemical properties of three WPI:TPS mixture systems at pH 3.0, pH 4.5, and pH 6.0 was studied. The electrostatic interaction between WPI and TPS at pH 4.5 and 6.5 could be improved by appropriate UT (20 min), as revealed by the higher turbidity and decreased absolute zeta-potential value of their mixture solution. Increases in β-sheet and random coil were observed for WPIs and WPI:TPS systems sonicated for 20 min. The surface hydrophobicity of the WPI:TPS system at pH 4.5 increased significantly with the duration of UT; moreover, this system showed enhanced emulsifying properties following appropriate UT.
On the whole, this thesis will provide important information on the impact of external factors, ultrasound, and protein types on the interaction of TPS with proteins, which may lead to the development and application of new protein-polysaccharide-based food ingredients or structured products.
Description
Partial Restriction
Keywords
Protein , Polysaccharide , Electrostatic interaction , Protein-polysaccharide complex , Ultrasound
Citation
Tian, L. 2024. The formation and physiochemical properties of Tremella fuciformis polysaccharide-proteins complex. PhD Thesis, University College Cork.