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

Abstract

Understanding the mechanism of interaction between food proteins and bioactives constitutes the preliminary step to design food grade nanocarriers. We investigated the interaction between cyanidin-3-O-glucoside (C3G), and 20nm-sized sodium caseinate nanoparticles (NaCas) at pH 7 and pH 2 by fluorescence spectroscopy and dynamic light scattering. The characterization of the C3G-NaCas interaction indicated that the fluorescence quenching mechanism was predominantly static. C3G interacted with two sets of binding sites with association constants Ka of 10 and 10M. Electrostatic interactions dominated at pH 7, while hydrophobic effects were the main force at pH 2. Interestingly, the two sets of binding sites were discriminated by ionic strength at pH 7. The binding of C3G slightly modified the average diameter of NaCas nanoparticles without alteration of its surface charge suggesting a complexation of C3G molecules in the internal casein structure. Thus, NaCas constitutes a putative nanocarrier for anthocyanins in new functional foods.

Unraveling the molecular mechanisms underlying interactions between caseins and lutein

“…On the other hand, the major size peak of NaCas solution exhibited the average hydrodynamic diameter around 20 nm. As expected, the average hydrodynamic diameter of PPCN was 10-fold higher than that observed for NaCas in aqueous solution (Casanova et al, 2018;Pan et al, 2013). This result is directly related to the highest content of colloidal calcium-phosphate in PPCN which plays an important role in casein micelle stabilization.…”

Occurrence, environmental implications and risk assessment of Bisphenol A in association with colloidal particles in an urban tropical river in Malaysia

“…Additionally, the binding interactions between colloidal particles (humic acid test suspension) and BPA are highly influenced by the conditions of the solution, since hydrophobic interactions, aromatic stacking and hydrogen bonds are taking place and developing at different temperatures, ionic strengths and pH values. The latter in particular is considered a vital variable that governs and influences the different interactions between dissolved organic matter and pollutants 20 . Depending on pH level, BPA can exist in three different forms in solutions (mono-anion, molecular and dianion) since it carries two phenol groups 21 .…”

The Chemical Reactivity of Anthocyanins and Its Consequences in Food Science and Nutrition

“…However, STP-NMR did not point protons specifically involved in the interaction. Cyanidin 3-glucoside expresses a rather high affinity for sodium caseinate (NaCas) [ 48 ]. Two binding sites were identified at pH = 2 and pH = 7, one of high affinity ( K b ≈ 1–7 × 10 6 M −1 depending on pH and T) and a second of lower affinity ( K b ≈ 2–7 × 10 5 M −1 ).…”