Characterization of interactions between chitosan and an anionic surfactant

Area of Science:

• Food Science
• Biopolymer Chemistry
• Physical Chemistry

Background:

• Chitosan, a cationic biopolymer, possesses unique properties valuable for the food industry.
• Its functionality often relies on interactions with anionic molecules like phospholipids and surfactants.

Purpose of the Study:

• To characterize the interaction between chitosan and sodium dodecyl sulfate (SDS), a model anionic surfactant.
• To understand the molecular basis of these interactions for food ingredient development.

Main Methods:

• Isothermal titration calorimetry (ITC) to measure binding thermodynamics.
• Surfactant-selective electrode (SSE) to quantify surfactant binding.
• Turbidity measurements to assess complex formation and light scattering.

Main Results:

• SDS binds strongly to chitosan through a highly exothermic interaction.
• Chitosan forms insoluble complexes with SDS, leading to significant light scattering.
• Chitosan saturation occurs at approximately 4 mM SDS per 0.1 wt % chitosan.
• The interaction is weakened by NaCl, indicating an electrostatic origin.

Conclusions:

• Chitosan and SDS exhibit strong electrostatic interactions, forming insoluble complexes.
• This understanding aids in designing functional chitosan-based food ingredients, potentially for cholesterol reduction or fat replacement.