Effect of blueberry extract addition on bovine sodium caseinate

LANARI, GABRIEL; HIDALGO, MARÍA EUGENIA; RISSO, PATRICIA

BIOCELL

INST HISTOL EMBRIOL-CONICET

Año: 2022

Anthocyanin/protein complex formation can be used to overcome chemical instability, that affects the health-beneficial properties and color stability of anthocyanins, by confining this active compound within a polymeric matrix for its encapsulation. This work aimed to study, using fluorescence spectroscopy, the interaction between sodium caseinate (NaCAS) and a blueberry extract (BEX) that contains anthocyanins. Furthermore, it assessed the effect of temperature (25, 37, and 42 °C) on the system. BEX was extracted from blueberries using a 0.25 M citric acid aqueous solution. The anthocyanin concentration of BEX was determined by the differential pH method based on the colored oxonium form predominating at pH 1.0 and the colorless hemiketal form at pH 4.5. The maximum excitation (EX) and emission (EM) wavelengths () of a 0.06% NaCAS solution in 10 mM Tris-HCl buffer pH 6.5 were determined at room temperature. EX and EM spectra were performed on a thermostatted Aminco Bowman Series 2 spectrofluorometer, with 286 nm and 340 nm determined as the EX and EM, respectively. Then, EM spectra of 0.06% NaCAS were performed in the absence and the presence of different amounts of BEX (anthocyanin concentration: 56 ± 6 mg/L) in the named buffer and at a given temperature (in duplicate). In addition, at the same pH and temperature, the fluorescence intensity (FI) of the BEX was measured. It observed that, as the BEX concentration increased, there was a decrease in FI without significant changes in the EM peak. This extinction of fluorescence (quenching) may be due to the collisions of the fluorophore (NaCAS) with the solvent molecules, decreasing the FI due to the loss of energy in a non-radiative way (dynamic quenching). Or it may be due to static quenching due to the formation of a non-fluorescent complex between the fluorophore and the BEX (quencher). To determine the quenching type, the Stern-Volmer constant (KSV) obtain from an adjustment of the F/F0 vs. BEX concentration graphics, where F is the FI in the presence of BEX and F0 is the FI in the absence of BEX. The values of KSV (mM-1) at 25, 35, and 42 °C were (0,549 ± 0,001), (0,572 ± 0,001), and (0,711 ± 0,001), respectively. It observed that there was a significant increase (p