Encapsulation of Thymol and Eugenol Essential Oils Using Unmodified Cellulose: Preparation and Characterization

Abstract

Essential oils (EOs) are volatile natural organic compounds, which possess pesticidal properties. However, they are vulnerable to heat and light, limiting their range of applications. Encapsulation of EOs is a useful approach to overcome some of these limitations. In this study, a novel emulsification technique is utilized for encapsulation of thymol (TY) and eugenol (EU) (EOs) within microcapsules with an unmodified cellulose shell. Use of low cost materials and processes can be beneficial in agricultural applications. In the encapsulation process, unmodified cellulose was dissolved in 7% aqueous NaOH at low temperature, regenerated to form a dispersion of cellulose hydrogels, which was rigorously mixed with the EOs by mechanical mixing followed by high-pressure homogenization (HPH). Cellulose:EO ratios of 1:1 and 1:8 utilizing homogenization pressures of 5000, 10,000 and 20,000 psi applied in a microfluidizer were studied. Light microscopy, high-resolution cryogenic scanning electron microscopy (cryo-SEM) and Fourier transform infrared spectroscopy (FTIR) revealed successful fabrication of EO-loaded capsules in size range of 1 to ~8 µm. Stability analyses showed highly stabilized oil in water (O/W) emulsions with instability index close to 0. The emulsions exhibited anti-mold activity in post-harvest alfalfa plants, with potency affected by the cellulose:EO ratio as well as the EO type; TY showed the highest anti-mold activity. Taken together, this study showed potential for anti-fungal activity of cellulose-encapsulated EOs in post-harvest hay.

Cellulose Nanocrystal-Based Emulsion of Thyme Essential Oil: Preparation and Characterisation as Sustainable Crop Protection Tool

“…These data are in line with our outcomes for the last NEs. The same trend was observed for cellulose-based EO MEs [33,35]. Finally, we can deduce that the crosslinking by Ca 2+ compensates for the inefficient coverage of the droplet surface due to excess oil, thus increasing the stability of NEs without increasing the CNCs amount.…”

“…CNCs-stabilised emulsions of clove, oregano, and thyme white essential oils showed enhanced antimicrobial activity against food-related microorganisms and larvae, stronger than that of pure EOs [29,33,34]. In addition, the encapsulation of thymol and eugenol EOs has been effectively achieved with a new emulsification method using an unmodified cellulose shell, achieving high antimould activity, which is useful for ecological pre-and postharvest pathogen control [35]. Thymol, the primary phenolic component of thyme (Thymus vulgaris) essential oil, displays rapid activity against gram-negative and gram-positive bacteria compared with other plant metabolites [36,37].…”

Plant Essential Oils: Dual Action of Toxicity and Egg-Laying Inhibition on Tetranychus urticae (Acari: Tetranychidae), Unveiling Their Potential as Botanical Pesticides

“…Research on the encapsulation materials of EOs is also crucial for the practical application of EOs in the field [ 38 ]. Lemon peel EO and its nanomaterials could enhance the insecticidal efficacy [ 25 ].…”

Sustainable Filters with Antimicrobial Action from Sugarcane Bagasse: A Novel Waste Utilization Approach

“…The C1 beads exhibited the highest EE; this measurement involved determining the final eugenol concentration in the liquid once the beads were completely dissolved. Considering the volatile nature of eugenol, the encapsulation process can benefit by protecting the bioactive compounds and facilitating a target delivery [26,27]. As we will discuss in further sections, the encapsulation efficiency influences the release kinetics and, consequently, the effectiveness of the antimicrobial filter.…”