Tailoring microalgal extract properties via non-thermal pretreatments: application-specific optimization in Chlorella vulgaris

Efficient disruption of the rigid cell wall of Chlorella vulgaris remains a major bottleneck in extracting high-value bioactives for food and nutraceutical applications. This study systematically compared five conditions—ultrasound (U), microwave (M), cold plasma (CP), cryogenic (C), and untreated control (UC)—as non-thermal pretreatments prior to supercritical CO₂ (SC-CO₂) extraction. Structural and compositional changes were analyzed using UV-Vis and FT-IR spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and field emission scanning electron microscopy (FE-SEM). The results revealed distinct effects of each pretreatment on pigment preservation, phenolic release, and antioxidant capacity. The UC condition yielded the highest pigment retention (62.14 mg/g chlorophyll, 32.62 mg/g carotenoids), while cryogenic treatment maximized phenolic content (31.05 mg GAE/g) and antioxidant capacity (56.21 mg TE/g). A multi-criteria decision-making framework, TOPSIS–Shannon entropy, was used to quantitatively rank the pretreatments based on application-specific parameters. The UC condition emerged as the most effective overall, highlighting its potential for pigment-rich food formulations. This is the first study to systematically link non-thermal pretreatment strategies to structure–function outcomes in C. vulgaris, offering a novel and actionable framework for microalgal extract customization in food versus nutraceutical sectors.