pH- and ionic strength-dependent interaction between cyanidin-3-O-glucoside and sodium caseinate

Area of Science:

• Food Science and Technology
• Nanotechnology
• Biochemistry

Background:

• Designing food-grade nanocarriers requires understanding interactions between food proteins and bioactive compounds.
• Cyanidin-3-O-glucoside (C3G) is a key anthocyanin with potential health benefits.
• Sodium caseinate nanoparticles (NaCas) are potential candidates for encapsulating bioactives.

Purpose of the Study:

• To investigate the interaction mechanism between cyanidin-3-O-glucoside (C3G) and sodium caseinate nanoparticles (NaCas).
• To characterize the binding sites and forces involved in the C3G-NaCas interaction at different pH levels.
• To evaluate the potential of NaCas as a nanocarrier for anthocyanins.

Main Methods:

• Fluorescence spectroscopy was employed to study the binding interaction and quenching mechanism.
• Dynamic light scattering (DLS) was used to analyze nanoparticle size and surface charge.
• Experiments were conducted at pH 7 and pH 2 to assess the influence of pH on the interaction.

Main Results:

• The interaction between C3G and NaCas nanoparticles was characterized by a predominantly static fluorescence quenching mechanism.
• C3G exhibited binding to two distinct sites on NaCas nanoparticles, with association constants of 10^6 M^-1 and 10^5 M^-1.
• Electrostatic interactions were dominant at pH 7, while hydrophobic interactions prevailed at pH 2. Ionic strength influenced binding site discrimination at pH 7. C3G binding slightly altered nanoparticle size but not surface charge, indicating encapsulation within the casein structure.

Conclusions:

• Sodium caseinate nanoparticles demonstrate a strong interaction with cyanidin-3-O-glucoside, driven by both electrostatic and hydrophobic forces depending on pH.
• The binding characteristics and minimal impact on nanoparticle integrity suggest NaCas is a suitable matrix for C3G.
• Sodium caseinate nanoparticles show significant potential as effective nanocarriers for anthocyanins in the development of novel functional foods.