Phycocyanin ultrasound assisted extraction from Spirulina (Arthrospira platensis) using sodium phosphate buffer solvent: Mass transfer modelling and stability test

Microalgae Spirulina (Arthrospira platensis) contains high protein content (55–70 %), consisting of approximately 20 % phycocyanin compounds as a photosynthetic pigment. Phycocyanin has antioxidant and anti-inflammatory properties. This study provides valuable insights involved mass transfer modelling and stability test of phycocyanin extract, leading to several important findings. Phycocyanin yield increases with temperature until 55 °C, beyond which denaturation reduces yield, highlighting the need for optimal temperature control during extraction. In the study at temperatures ranging from 30 °C to 50 °C, the mass transfer coefficients (kca) values ranged from 0.0229/min to 0.2592/min, the effective diffusivity (De)​ values ranged from 0.112 to 0.0519 cm²/min or 1.87 × 10⁻⁸ to 8.64 × 10⁻⁸ m²/s, and the equilibrium constants (K) values ranged from 106 to 572. The mathematical modelling of mass transfer phenomena was validated through comparison with experimental data, and all models showed R-squared (R²) values greater than 0.99, indicating a strong fit. Statistical analysis confirms temperature significantly impacts mass transfer parameters (kca, De, K) in phycocyanin extraction (p < 0.05). Narrow confidence intervals for kca and De indicate high precision, while K shows greater variability, suggesting additional influencing factors besides the temperature. The mass transfer parameter constants increased with temperature due to enhanced molecular collisions, which accelerate solute diffusion and transport within the extraction medium. The degradation behavior of phycocyanin over seven days demonstrates that light exposure significantly accelerates the degradation process of bioactive compounds derived from microalgae. According to the kinetic modelling, the highest R² value among the three reaction rate models was observed for the first-order reaction rate equation, hence indicates that the first-order reaction rate equation accurately represents the degradation of phycocyanin pigment.