Nanoencapsulation of Thyme Essential Oils: Formulation, Characterization, Storage Stability, and Biological Activity

Nanoencapsulation of Ocimum basilicum L. and Satureja montana L. Essential Oil Mixtures: Enhanced Antimicrobial and Antioxidant Activity

Background/Objectives: Essential oils (EOs) represent a natural alternative to chemical additives due to their biological activity. This study evaluated the antimicrobial and antioxidant activities of basil and winter savory EO mixtures, their interactions, and the biological potential of chitosan-based nano-encapsulated EO mixtures. Methods: Mixtures of basil and winter savory EOs (ratios 1:1, 2:1, 4:1, 8:1, and 16:1) were analyzed for chemical composition via GC-MS. Antimicrobial activity was assessed using minimal inhibition (MIC) and bactericidal (MBC) concentration assays, and interactions were quantified with fractional inhibitory concentration indices (FICIs). Antioxidant activity was evaluated using the DPPH assay, with combination indices used to interpret interaction effects. Chitosan-based nanoparticles were made with the selected oil mixture (2:1), after which characterization and biological activity were performed. Results: The EO mixture with 2:1 ratio exhibited the strongest joint activity, with synergistic or additive effect against four out of six analyzed microorganisms. Antioxidant activity improved with higher basil proportions, with the 16:1 ratio achieving the lowest EC50 value of 0.052 mg/mL after 120 min and demonstrating synergistic effects at all tested ratios. Higher basil EO content also masked the strong odor of winter savory EO. The biological activity of chitosan-based nanoparticles was increased by encapsulation of the EO mixture (2:1), with an encapsulation efficiency of 75.39%. Conclusions: The EO mixture (2:1) showed best antimicrobial efficacy, with synergistic or additive effects. The nano-encapsulated mixture showed good biological potential with effective and complete odor neutralization. These results indicate the potential of basil and winter savory essential oil mixtures for sustainable food preservation applications.

Eryngo essential oil nanoemulsion stabilized by sonicated-insect protein isolate: An innovative edible coating for strawberry quality and shelf-life extension

New bioactive coatings with eryngo essential oil (EEO) nanoemulsions stabilized by ultrasonically-treated lesser mealworm protein isolate (LMPI) were developed to extend strawberry shelf life and quality. EEO due to high carvone (43.03 %), phenolics (87.45 mg gallic acid equivalent/g), flavonoids (13.56 mg quercetin equivalent/g), and carotenoids (635.07 mg/kg) contents exhibited a significant antioxidant activity comparable to ascorbic acid (AA) and BHT. Nanoemulsions stabilized with 9 % sonicated LMPI showed smaller droplet size, higher negative ζ-potential, and greater stability, turbidity, and encapsulation efficiency of EEO compared to those stabilized with native LMPI. The FTIR spectra showed that sonicated LMPI had structural changes enhancing its emulsifying activity, with key peaks indicating the presence of hydrogen bonds, carbonyl groups, and protein conformations in both EEO and LMPI. Strawberries coated with optimal EEO-loaded nanoemulsions showed superior quality with minimal storage-dependent physicochemical, textural, color, and sensory changes compared to control samples. This edible coating also maintained higher total monomeric anthocyanin and AA contents with lower peroxidase activity during storage than EEO-based coatings. However, no significant difference in superoxide dismutase activity between samples covered by EEO and EEO-loaded nanoemulsions over 14 days of storage was found. Bioactive nanoemulsions stabilized by insect proteins would be an eco-friendly and safe approach to upholding quality standards in stored fruits and vegetables.

Antibacterial effects of thyme oil loaded solid lipid and chitosan nano-carriers against Salmonella Typhimurium and Escherichia coli as food preservatives

OBJECTIVES

Escherichia coli and Salmonella Typhimurium are frequent causes of foodborne illness affecting many people annually. In order to develop natural antimicrobial agents against these microorganisms, thyme oil (TO) was considered as active antibacterial ingredient. TO contains various bioactive compounds that exhibit antimicrobial properties. To increase the antibacterial effects and stability of thyme oil, two promising carrier systems, solid lipid nanoparticles (SLN) and chitosan nanoparticles have been fabricated in this study.

METHODS

Nanoparticles were made using natural-based lipids and polymers by a probe sonication method. They were characterized using infrared spectrometry (FTIR), transmission electron microscopy (TEM), particle size, cytotoxicity, etc. Antibacterial effects of TO, thyme oil loaded in SLN (TO-SLN) and thyme oil loaded in chitosan nanoparticle (TO-CH) was evaluated against E. coli and S. typhimurium using Minimum inhibitory/bactericidal concentrations (MIC/MBC) determination. Encapsulation efficiency (EE%) and drug release profile were also studied in vitro.

RESULTS

TEM analysis revealed spherical/ovoid-shaped particles with clear edges. TO-SLN had an average size of 42.47nm, while TO-CH had an average size of 144.8nm. The Encapsulation efficiency of TO-CH and TO-SLN nanoparticles were about 81.6±1% and 73.4±1%, respectively. Results indicated 92% cumulative release in TO-CH in comparison with 88% in TO-SLN in 72 h. MIC against E. coli and S. typhimurium for TO-CH, TO-SLN, and pure TO were 4 and 1.5 μg/mL, 60 and 40 μg/mL, and 180-150 μg/mL, respectively.

CONCLUSION

Nanoencapsulation of thyme oil significantly potentiated its antimicrobial effects. TO-CH exhibited a significantly higher antibacterial effect compared to TO-SLN (6-fold) and pure thyme oil (more than 10-fold).

Nanoencapsulated Essential Oils for Post-Harvest Preservation of Stored Cereals: A Review

Cereal grains are frequently attacked by microorganisms and insects during storage and processing, which negatively affects their quality, safety, and market value. Therefore, protecting stored grains from microbial contamination is crucial for food industries, farmers, public health associations, and environmental agencies. Due to the negative impact of synthetic gray chemicals, antimicrobial plant-based essential oils (EOs) can serve as alternative, safer, environmentally friendly preservatives that can prolong the shelf life of cereals. However, high volatility, low solubility, hydrophobicity, and quick oxidation limit their practical applicability. Using nanotechnology for the nanoencapsulation of EOs into polymeric matrices allows sustained release and ensures targeted delivery without significantly altering the organoleptic attributes of cereals, making EOs a new-generation green preservative. This ultimately overcomes the challenges of practical applications. The application of nanoencapsulated EOs in grain storage provides an effective and novel defense against microbes, insects, and other contaminants. Hence, the current review thoroughly examines the preservative potential of nanoencapsulated EOs in terms of antimicrobial and insecticidal efficacy for protecting stored cereal grains. It also highlights the challenges encountered during application and the safety concerns of using nanoencapsulated EOs in protecting cereal grains during post-harvest storage.

Enhancing therapeutic effects alginate microencapsulation of thyme and calendula oils using ionic gelation for controlled drug delivery

This study focuses on encapsulating and characterizing essential oils such as thyme and calendula oils, which are known for their therapeutic properties but are limited in pharmaceutical formulations due to their low water solubility and instability, with alginate microspheres. Alginate presents an excellent option for microencapsulation due to its biocompatibility and biological degradability. The ionic gelation (IG) technique, based on the ionic binding between alginate and divalent cations, allows the formation of hydrogel materials with high water content, mechanical strength, and biocompatibility. The microspheres were characterized using FT-IR, SEM, and swelling analyses. After determining the encapsulation efficiency and drug loading capacity, the microspheres were subjected to dissolution studies under simulated digestion conditions. It was observed that the swelling percentage of the microspheres in simulated gastric fluid (SGF) ranged from ∼15% to 100%, while in simulated intestinal fluid (SIF) it ranged from ∼150% to 325%. Thyme oil, with low viscosity, exhibited higher encapsulation efficiency than marigold oil. The highest encapsulation efficiency was observed in A-TO-2 microspheres, while the highest drug loading capacity was observed in A-TO-5 microspheres. During the examination of the dissolution profiles of the microspheres, dissolution rates ranging from 10.98% to 23.56% in SGF and from 52.44% to 63.20% in SIF were observed.

Enhancing Antimicrobial Activity of Thyme Essential Oil Through Cellulose Nano Crystals-Stabilized Pickering Emulsions

Essential oils (EOs), such as thyme essential oil (TEO), are widely known for their antimicrobial properties; however, their direct application in food systems is limited due to their poor stability, which affects their efficacy. This study aims to improve the stability and antimicrobial efficacy of TEO by encapsulating it in Pickering emulsions stabilized with cellulose nanocrystals (CNC). Two formulations of Pickering emulsions with 5% and 10% TEO were prepared and compared to traditional surfactant-based emulsions. The stability of the emulsions was assessed over 21 days, and particle size, zeta potential, Raman spectroscopy, and FTIR were used for characterization. The antimicrobial activity was tested against several foodborne pathogens, with minimum inhibitory concentration (MIC) values determined. The 10% TEO Pickering emulsion showed antimicrobial activity, with MIC50 values of 4096 µg/mL against Staphylococcus aureus and Escherichia coli, while the 5% TEO formulation had no effect at MIC50 > 8192 µg/mL. The CNC-stabilized Pickering emulsions exhibited superior stability, showing no phase separation over 21 days. The findings suggest that CNC-stabilized Pickering emulsions are effective at improving the stability and antimicrobial performance of TEO, making them a promising natural preservative for food packaging and safety. Further research is recommended to optimize the formulation and broaden TEO's application in food preservation.

Safety and efficacy of a feed additive consisting of an essential oil derived from the flowering tops of Thymbra capitata (L.) Cav. (Spanish type origanum oil) for use in all animal species (FEFANA asbl)

Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the safety and efficacy of an essential oil from the flowering tops of Thymbra capitata (L.) Cav. (Spanish type origanum oil) when used as a sensory additive in feed and in water for drinking for all animal species. The EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) concluded that the additive under assessment is considered safe up to the maximum use level in complete feed of 15 mg/kg for poultry species, 30 mg/kg for pigs and horses, 20 mg/kg for ruminants, 25 mg/kg for rabbits, dogs, cats and ornamental fish, and 125 mg/kg for salmonids. These conclusions were extrapolated to other physiologically related species. For any other species, the additive is safe at 15 mg/kg complete feed. The FEEDAP Panel considered that the use level in water for drinking is safe provided that the total daily intake of the additive does not exceed the daily amount that is considered safe when consumed via feed. The use of the additive in animal feed under the proposed conditions of use is safe for the consumer and the environment. Regarding user safety, the essential oil under assessment should be considered as an irritant to skin and eyes and as a dermal and respiratory sensitiser. Since T. capitata and its preparations were recognised to flavour food and its function in feed would be essentially the same as that in food, no further demonstration of efficacy was considered necessary.

Comparative analysis of chemical profiles, antioxidant, antibacterial, and anticancer effects of essential oils of two Thymus species from Montenegro

The essential oils of Thymus vulgaris (TVEO) and Thymus serpyllum (TSEO) show different biological activities. The aim of the study was to evaluate the biological activities of TVEO and TSEO from Montenegro. The main components of TVEO were p-cymene (29.52%), thymol (22.8%) and linalool (4.73%) while the main components of TSEO were p-cymene (19.04%), geraniol (11,09%), linalool (9.16%), geranyl acetate (6.49%) and borneol (5.24%). Antioxidant activity determined via DPPH for TVEO was 4.49 and FRAP 1130.27, while for TSEO it was estimated that DPPH was 4.88 μL/mL and FRAP was 701.25 μmol FRAP/L. Both essential oils were active against all tested bacteria, with the highest level of sensitivity of E. coli with MIC of 1.5625 μL/mL. Essential oils showed strong cytotoxic effects on human cancer cell lines, with IC50 values ranging from 0.20 to 0.24 μL/mL for TVEO and from 0.32 to 0.49 μL/mL for TSEO. TVEO caused apoptosis in cervical adenocarcinoma HeLa cells through activation of caspase-3 and caspase-8, while TSEO caused apoptosis through caspase-3. EOs decreased levels of oxidative stress in normal MRC-5 cells. HeLa cells treated with TVEO had reduced MMP2 expression levels, while cells treated with TSEO had lowered MMP2 and MMP9 levels. The treatment of HeLa cells with TVEO increased the levels of miR-16 and miR-34a, indicating potential tumor-suppressive properties. Our findings suggest that Thymus essential oils may be considered as good candidates for further investigation as cancer-chemopreventive and cancer-therapeutic agents.

Plant protein-based emulsions for the delivery of bioactive compounds

Emulsion-based delivery systems (EBDSs) can be used as effective carriers for bioactive compounds (bioactives). Recent studies have shown that plant proteins (PLPs) have the potential to be utilized as stabilizers of emulsions for loading, protection and delivery of bioactives. Different strategies combining physical, chemical and biological techniques can be applied for alteration of the structural characteristics and improving the emulsification and encapsulation performance of PLPs. The stability, release, and bioavailability of the encapsulated bioactives can be tailored via optimizing the processing conditions and formulation of the emulsions. This paper presents cutting-edge information on PLP-based emulsions carrying bioactives in terms of their preparation methods, physicochemical characteristics, stability, encapsulation efficiency and release behavior of bioactives. Strategies applied for improvement of emulsifying and encapsulation properties of PLPs used in EBDSs are also reviewed. Special emphasis is given to the use of PLP-carbohydrate complexes for stabilizing bioactive-loaded emulsions.

Biopolymer- and Lipid-Based Carriers for the Delivery of Plant-Based Ingredients

Natural ingredients are gaining increasing attention from manufacturers following consumers’ concerns about the excessive use of synthetic ingredients. However, the use of natural extracts or molecules to achieve desirable qualities throughout the shelf life of foodstuff and, upon consumption, in the relevant biological environment is severely limited by their poor performance, especially with respect to solubility, stability against environmental conditions during product manufacturing, storage, and bioavailability upon consumption. Nanoencapsulation can be seen as an attractive approach with which to overcome these challenges. Among the different nanoencapsulation systems, lipids and biopolymer-based nanocarriers have emerged as the most effective ones because of their intrinsic low toxicity following their formulation with biocompatible and biodegradable materials. The present review aims to provide a survey of the recent advances in nanoscale carriers, formulated with biopolymers or lipids, for the encapsulation of natural compounds and plant extracts.

Delivery systems for fucoxanthin: Research progress, applications and future prospects

Fucoxanthin is a special kind of keto-carotenoid found only in algae. The unique structure of fucoxanthin endows it with extraordinary biological activities, which are of great significance to improve food quality and enhance human health. However, due to its highly unsaturated structure, fucoxanthin also suffers from some limitations, such as instability, poor water solubility and low bioavailability. Therefore, although its content is relatively abundant, its applications in the food industry are extremely scarce. In recent years, there have been many reports on the preparation and characterization of delivery systems for fucoxanthin. These well-designed delivery systems can efficaciously alleviate the instability of fucoxanthin under adverse conditions, thereby improving its oral bioavailability. Thus, this review emphatically summarizes the delivery systems that are widely used to encapsulate, protect and release fucoxanthin. Besides, the influence of delivery systems on the absorption of fucoxanthin by intestinal epithelial cells is highlighted. The applications and future development trends of delivery systems for fucoxanthin are also discussed. The extraction of fucoxanthin, development of novel delivery systems, sensory evaluation and toxicity studies, and industrial production may be promising research directions in the future. Overall, this review provides guidance for the development of fucoxanthin-loaded delivery systems.