Sustained Antifungal Protection of Peanuts Using Encapsulated Essential Oils

Abstract

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 (Origanum compactum) and myrtle (Myrthus communis) EOs (75:25, w/w) 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 A. flavus (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 Aspergillus sections Flavi and Nigri, Penicillium spp., Rhizopus, Fusarium, and Alternaria. 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.