Long-Term Refrigerated Storage of Hyssopus officinalis and Agastache foeniculum (Pursh) Kuntze Essential Oils: Implications for Sustainable Food Preservation

Essential oils (EOs) are promising plant-derived antimicrobial agents for food preservation, and their long-term storage stability is relevant for the continued use of seasonally produced aromatic-plant resources. This study evaluated the chemical profile stability and antibacterial activity of EOs from Hyssopus officinalis L. and Agastache foeniculum (Pursh) Kuntze over a two-year refrigerated storage period, with three annual sampling points. Chemical composition was determined by GC–MS, and temporal variations were assessed by principal component analysis (PCA). Antibacterial activity against Escherichia coli, Staphylococcus aureus, Listeria monocytogenes, and Salmonella Enteritidis was determined using minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) assays. Hyssop EO maintained its characteristic profile, although isopinocamphone decreased from 38.62% to 26.01%, accompanied by increased relative contributions of sesquiterpenes. Anise hyssop EO maintained a stable, estragole-dominated profile (72.89–70.16%). PCA provided a descriptive visualization of temporal changes in the chemical profiles of both EOs. Antibacterial activity remained detectable throughout storage, with EO- and strain-dependent changes. Hyssop EO maintained measurable activity against E. coli (MIC/MBC = 11.36 μL/mL), whereas anise hyssop EO maintained measurable activity against S. Enteritidis (MIC = 5.68 μL/mL; MBC = 11.36 μL/mL). These findings indicate that both batches of EOs preserved measurable antibacterial activity, supporting their potential continued use in food preservation and the more efficient utilization of seasonally produced aromatic-plant resources.