High-pressure processing (HPP) of phycocyanin extract solutions: Enhancing stability through molecular interactions

C-Phycocyanin (PC) has been proposed as a replacement for synthetic colors in foods. However, C-PC stability is adversely affected during food processing due to exposure to high temperature, pressure, oxygen concentration or extreme pHs. This study assessed the degradation mechanisms of C-PC under a nonthermal pasteurization technology, i.e., High-Pressure Processing (HPP), and identified potential processing protocols to arrest C-PC instability at low pH. Aqueous C-PC solutions (pH:4–6) were subject to HPP (500–600 MPa) for 1–5 min. C-PC stability was monitored based on changes in the photophysical properties of its fluorophores (phycocyanobilin chromophore and aromatic amino acid residues) and particle size. pH significantly affected C-PC's stability towards HPP (<stability at < pH). Sharper hypsochromic (blue) shifts, lower intensity, and higher anisotropy were observed as pressure and treatment time increased, which suggested conformational changes in C-PC's polypeptides, followed by aggregation. pH adjustment after HPP treatments resulted in a significant reduction in color loss and aggregation, possibly due to partial stabilization of the polypeptide subunits' conformation.