Taguchi Design and MFA Screening of Corncob-Derived Cellulose and Lignin Particles for Photoprotective Cocoa Pickering Emulsions

Corncob, a maize by-product, contains cellulose and lignin fractions that act as complementary Pickering stabilizers. Their combined use and relative proportion have been scarcely investigated. This study screened corncob-derived cellulose particles (CP) and lignin particles (LP) as dual stabilizers in cocoa-loaded Pickering emulsions using a Taguchi L8 design combined with multiple factor analysis (MFA). CP were obtained by sulfuric acid hydrolysis of bleached cellulose pulp and LP by pH-shift precipitation from alkali-solubilized lignin. Both fractions formed colloidal aggregates near 3 µm; LP were strongly anionic (ζ ≈ −32 mV) and CP nearly neutral (ζ ≈ +2 mV). Four factors were screened at two levels: CP:LP ratio (75:25/25:75), particle concentration (0.25/1.00% w/v), sunflower oil fraction (10/30% v/v), and cocoa concentration (0.5/2.0% w/v). Emulsions were prepared by Ultra-Turrax homogenization (13,500 rpm, 5 min) at 40 °C. Six responses were measured: droplet size (Sauter diameter D32, µm), sedimentation (%, 24 h), creaming index (%, 24 h), antioxidant capacity (TEAC, µmol TE/mL via DPPH), phenolic compounds (gallic acid and vanillyl alcohol, mg/mL, HPLC), and zeta-potential resilience (|ζ| loss after 10 days of storage). The last three were also assessed before and after 5 h of UV-C exposure. D32 ranged from 5.86 to 62.2 µm and showed the largest dependence on particle concentration (S/N range = 7.19). Sedimentation (0.09–1.23%) depended mainly on oil fraction (S/N range = 9.90). TEAC photoprotection depended mainly on CP:LP ratio (2.82). Phenolic retention and zeta resilience depended mainly on cocoa concentration (10.6 and 13.3). Creaming index remained low across all runs (3.85–8.70%). MFA identified two independent axes: a functional-protective dimension (Dim 1, 41%), in which antioxidant, phenolics, and charge blocks contributed jointly over 90%, and a morphological-physical dimension (Dim 2, 23%). RV coefficients indicated high covariation between phenolics and charge (0.79) and between phenolics and antioxidant capacity (0.56). CP:LP ratio produced opposing optima: 75:25 favored physical stability and 25:75 favored antioxidant and phenolic protection. Particle concentration (0.25%) and cocoa load (2.0%) were optimal across all six responses, while the CP:LP ratio defined a trade-off between physical and functional performance that intermediate formulations may address.