Articles

C-phycocyanin (C-PC) is a high-value pigment–protein in <i>Spirulina</i> biomass whose thermolability makes it vulnerable to degradation during post-harvest drying, yet freeze-drying—the gold-standard preservation method—remains prohibitively energy-intensive for large-scale production. This study investigated whether controlled-humidity air drying can preserve C-PC content and its antioxidant functionality in dried biomass comparably to freeze-drying. Wet <i>Spirulina</i> biomass (25 g fresh weight) was dried under nine factorial combinations of temperature (25, 40, and 60°C) and relative humidity (20, 30, and 40%) using a temperature–humidity chamber, with freeze-drying (FD) as the reference. C-PC was extracted, quantified spectrophotometrically along with allophycocyanin and chlorophyll, and its purity index (A<SUB>620</SUB>/A<SUB>280</SUB>) and antioxidant activity (DPPH radical scavenging, IC<SUB>50</SUB>, and ascorbic acid equivalent antioxidant capacity) were determined. Statistical analyses included one-way ANOVA with Tukey's post-hoc test and partial Pearson correlation. Air drying at 25°C yielded C-PC contents of 184.39 - 194.72 mg g<SUP>-1</SUP> DW (98 - 104% of the FD reference, 188.11 mg g<SUP>-1</SUP> DW) with food-grade purity indices of 0.95 - 1.00, whereas drying at 40°C and 60°C reduced C-PC to 76 - 85% and 58 - 63% of the FD value, respectively. Partial correlation analysis identified temperature as the dominant determinant of C-PC loss (Pearson <i>r</i> = -0.90 to -1.00), while relative humidity exerted a secondary, modulatory influence. The 25°C air-dried C-PC retained 86 - 87% of the antioxidant capacity of a commercial C-PC reference standard, approaching the 94% retention achieved by freeze-drying. These findings demonstrate that controlled-humidity air drying at 25°C and 20 - 30% relative humidity effectively preserves both C-PC yield and bioactivity at levels comparable to freeze-drying, offering a potential scalable and low-cost drying alternative for the <i>Spirulina</i> nutraceutical industry