ε-Poly-L-Lysine and Oregano Essential Oil Synergistically Extend Strawberry Shelf Life by 5 Days

The global food industry faces significant challenges with perishable fruit spoilage, primarily due to microbial contamination, leading to substantial economic losses and food waste. Current preservation methods often rely on synthetic chemicals, which raise consumer concerns regarding safety and environmental impact. There is a pressing need for natural, effective, and sustainable alternatives that can enhance food safety and extend shelf life without compromising quality. This study explores the potential of ε-poly-L-lysine (ε-PL), a natural antimicrobial peptide, in combination with essential oils to address this critical gap in fruit preservation.

Researchers developed a novel synergistic antibacterial system combining ε-poly-L-lysine (ε-PL) and oregano essential oil (OEO). They screened ε-PL with seven different essential oils, identifying OEO as having the strongest synergistic interaction. The antibacterial efficacy was evaluated using integrated in vitro assays, including assessments of bacterial cell membrane disruption and intracellular component leakage. The most effective combination was then applied in vivo to strawberries to assess its impact on microbial counts, shelf life, and quality parameters. An in silico molecular docking analysis was also performed to understand the binding mechanisms.

The ε-PL/OEO combination demonstrated significantly enhanced antibacterial efficacy compared to individual agents, primarily through disruption of bacterial cell membranes and leakage of intracellular components. In silico molecular docking analysis revealed a strong binding energy of -7.8 kcal/mol, supporting the synergistic interaction. Applied in vivo to strawberries, the ε-PL/OEO treatment effectively reduced total viable counts to < 3.0 log CFU/g. This potent antimicrobial action translated into a substantial improvement in fruit longevity and quality.

The treatment extended the shelf life of strawberries by 5 days when stored at room temperature. Furthermore, the treatment effectively preserved key quality parameters, maintaining pH at 2.69, titratable acidity at 0.493%, total soluble solids at 7.4 °Brix, and reducing sugars at 0.772 g/100 g. Weight loss was also minimized to < 2.0%, indicating superior preservation of fruit integrity.