Sustained Antifungal Protection of Peanuts Using Encapsulated Essential Oils

Essential oils (EOs) are promising bio-preservatives for oilseeds; however, their high volatility and strong aroma limit practical applications. In this study, we developed a dual-size microencapsulated formulation of oregano (<i>Origanum compactum</i>) and myrtle (<i>Myrthus communis</i>) EOs (75:25, <i>w</i>/<i>w</i>) using gelatin-gum arabic complex coacervation, and evaluated its antifungal efficacy and effect on seed viability in peanuts. GC-MS analysis of the EO blend identified carvacrol (33.83%) as the dominant constituent. The microcapsules exhibited an encapsulation efficiency of 83.56% and were produced in a 70% small/30% large particle ratio to ensure both immediate and sustained vapor release. In vapor-phase assays against toxigenic <i>A. flavus</i> (RP-6), both free and encapsulated EOs inhibited fungal growth in a dose-dependent manner and achieved complete suppression at concentrations ≥0.2 µL mL^-1, whereas the wall material alone showed no activity. In a 120-day microcosm storage experiment (0.2 mg EO g^-1 kernels; 0.96 mg microcapsules g^-1), treated peanuts showed an immediate reduction in total fungal load from 3.52 to 1.48 log₁₀ CFU g^-1 (≈58%), which stabilized near 1.42-1.43 log₁₀ CFU g^-1 up to 90 days, while the control samples increased to 4.25 log₁₀ CFU g^-1 by day 120. The formulation effectively suppressed major storage fungi, including <i>Aspergillus</i> sections <i>Flavi</i> and <i>Nigri</i>, <i>Penicillium</i> spp., <i>Rhizopus</i>, <i>Fusarium</i>, and <i>Alternaria</i>. The antioxidant activity (DPPH assay) was retained after encapsulation (IC₅₀: 0.52 mg mL^-1 encapsulated vs. 0.58 mg mL^-1 free). Germination power remained comparable to the control throughout storage (≈50-52%), indicating no adverse impact on seed viability. These findings demonstrate that vapor-active, dual-size microencapsulation of oregano-myrtle EOs offers a practical and sustainable approach to enhance peanut safety during storage without compromising germination potential.