The Antimicrobial and Antioxidant Effects of Bilayer Films Based on Polylactic Acid ( <scp>PLA</scp> )/Chitosan: Starch Containing Bitter Orange Essential Oil on the Fresh Rainbow Trout ( <i>Onchorhynchus mykiss</i> ) Fillet

This study investigated the antibacterial properties of polylactic acid (PLA)/chitosan: starch films incorporated with bitter orange essential oil (BOEO) for preserving rainbow trout fillets. Three BOEO concentrations (0.7%, 1.4%, and 2.1% w/w) were incorporated via casting. Increased BOEO concentration enhanced film hydrophobicity and thermal resistance, but reduced tensile strength while increasing elongation. Atomic force microscopy revealed altered surface roughness. Antibacterial testing showed optimal activity against both Gram-positive and Gram-negative bacteria at 1.2% BOEO. Films containing 1.2% BOEO were applied to rainbow trout fillets, significantly reducing spoilage bacteria (total bacterial count, psychrotrophic, lactic acid bacteria, and Enterobacteriaceae), slowing chemical spoilage (pH and TBA values), and minimizing weight loss during 16 days of refrigerated storage (4°C). These results demonstrate the potential of BOEO-incorporated PLA/chitosan: starch films for extending the shelf life of rainbow trout.