Improved thermal stability of phycocyanin under acidic conditions by forming soluble complexes with polysaccharides

Phycocyanin, a natural blue-colored protein–chromophore complex, forms insoluble aggregates under acidic conditions and loses blue hue during heating. Targeting these issues, phycocyanin was complexed with six polysaccharides (κ-/ι-/λ-carrageenans, xanthan gum, high-methoxyl pectin, guar gum), respectively; the colloidal color behaviors of complexes were examined at pH 3.0 before after heating (60 °C/80 °C, 30 min). A simple HCl titration strategy developed to inhibit associative phase separation commonly occurs complexation. Soluble achieved ι-carrageenan, demonstrating good stability without Fluorescence analyses suggest that electrostatic complexation between mentioned three reinforced by hydrophobic interactions. The ι-carrageenan–phycocyanin complex exhibits best stabilities according laser diffraction particle size analysis colorimetry. Electrophoresis suggests highly negatively charged carrageenans, particularly display high affinity entrapment efficiency phycocyanin. Circular dichroism further reveals ability carrageenans stretch phycocyanin's tertiary structures while maintaining native-like secondary structures, which inhibits changes in resulted from dense interchromophore couplings α-helical coiled-coils. Overall, this work dissects polysaccharide–phycocyanin common beverage processing provides fundamental insights into conformational modifications on imparted improved would facilitate future application foods/beverages as substitutes artificial pigments.