Enhanced Strawberry Preservation Using H. pluvialis Residue-Based Films

Novel films composed of Haematococcus pluvialis residue (HPR), chitosan (CS), citric acid (CA), glycerol (GL), and calcium chloride (CaCl₂) were developed to improve strawberry preservation. The rheological, structural, and functional properties of film-forming aqueous solutions (CS/CA, CS/CA/GL, CS/CA/GL/Ca, CS/CA/GL/Ca/HPR) were analyzed. It revealed HPR-induced shear-thinning behavior ( η = 2260   Pa·s) and enhanced rigidity (G'' = 750.51   Pa at 100   rad/s) via hydrogen bonding and Ca²⁺ crosslinking. FTIR and UV-vis spectra confirmed molecular interactions between carboxyl groups of HPR and amino residues of CS. The films with 0.6% HPR exhibited superior mechanical strength (tensile strength: 12.16   MPa; elongation at break: 135.36%), reduced water vapor permeability (1.14 × 10 -10 gm ⁻¹ s ⁻¹ Pa ⁻¹ ), and antioxidant activity (73.16% DPPH scavenging) than CS film. Antibacterial efficacy against S. aureus and E. coli peaked at 0.8% HPR. The weight loss of strawberry was reduced by using the HPR film (13.08% vs. control: 29.5%), retained ascorbic acid (19.98   mg/100   g vs. control: 6.75   mg/100   g). The shelf life of strawberries was extended by 30 days, which is 15 days longer than that of those wrapped with polyethylene film. The polysaccharides, astaxanthin, and algal proteins in HPR improved barrier properties, oxidative stability, and microbial resistance. These results highlight the potential of HPR films as sustainable, multifunctional packaging to extend fruit shelf life.