Food preservation is a major challenge faced by the food industry. To prevent food from spoiling and deteriorating and extend its shelf life, preservatives are often added to food. The existing food preservatives include chemical preservatives and natural source preservatives. Although chemical preservatives can quickly and efficiently inhibit food spoilage, they are not easy to decompose and remain on the surface of food, posing a great safety hazard to human health and the environment. Plant essential oils, as an important source of natural preservatives, are highly volatile preservatives. They create an antibacterial atmosphere around food through direct contact or fumigation, thereby achieving preservation and freshness.

Plant essential oils possess various biological activities such as antioxidant, antibacterial and insect repellent properties. They can effectively inhibit the oxidation and deterioration of fruits and vegetables, prevent the growth of spoilage microorganisms and avoid pest infestation. They are excellent preservatives for the preservation of fruits and vegetables.

Key Essential Oils: Mechanisms and Targeted Food Applications

Different Essential Oils excel in specific food matrices due to their unique compositions:

1. Oregano & Thyme Oil (Carvacrol/Thymol):

Mechanism: High phenolic content (carvacrol, thymol) provides exceptional broad-spectrum antimicrobial activity (bacteria, fungi) via membrane disruption.

Target Foods: Highly effective in meat and poultry products (against L. monocytogenes, S. enterica), fresh produce (leafy greens, tomatoes against E. coli O157:H7, Salmonella), dairy products (cheese against molds and yeasts), and marinades/oil-based dressings. Often used in edible coatings.

2. Clove Oil (Eugenol):

Mechanism: High eugenol content confers strong antifungal and antibacterial activity, along with significant antioxidant properties.

Target Foods: Particularly effective for baked goods (against mold growth), fruit purees and juices (against spoilage yeasts and molds), processed meats (antioxidant and antimicrobial), and fish products. Its warm aroma suits spice blends.

3. Cinnamon Oil (Cinnamaldehyde):

Mechanism: Cinnamaldehyde is a potent antifungal and antibacterial compound, especially effective against Listeria monocytogenes.

Target Foods: Excellent for fruit preservation (apple, pear, peach coatings against Botrytis, Penicillium), fruit juices and beverages, bakery products, and meat systems. Often applied via vapor phase or encapsulation to manage strong flavor.

4. Rosemary & Sage Oil (Carnosic Acid, Carnosol, Rosmarinic Acid):

Mechanism: Rich in phenolic diterpenes, these oils are primarily powerful antioxidants, inhibiting lipid oxidation. They also possess moderate antimicrobial activity.

Target Foods: Ideal for stabilizing fats, oils, and fatty foods (e.g., frying oils, salad dressings, nuts, snacks), processed meats (delaying rancidity in sausages, patties), and shelf-stable ready meals. Extracts are also widely used.

5. Citrus Oils - Lemon, Orange, Grapefruit (Limonene):

Mechanism: High limonene content provides good antifungal activity, pleasant aroma, and notable antioxidant effects.

Target Foods: Widely used in fruit coatings (citrus fruits, apples, melons against Penicillium spp.), beverages, confectionery, and dairy desserts (yogurts, custards). Their fresh scent is a major advantage.

6. Tea Tree Oil (Melaleuca alternifolia) (Terpinen-4-ol):

Mechanism: High terpinen-4-ol content drives strong broad-spectrum antimicrobial activity, particularly potent against fungi.

Target Foods: Shows significant promise in post-harvest fruit preservation (especially berries, stone fruits against Botrytis cinerea and other fruit rot fungi) and vegetable storage. Research focuses on coatings and vapor phase.

Overcoming Application Challenges

Direct use of pure EOs is limited by strong flavor, volatility, and low water solubility. Advanced application strategies are key:

• Edible Coatings & Films: Incorporating EOs into chitosan, alginate, or protein-based coatings for fruits, vegetables, cheese, and meat provides localized, controlled release.

• Encapsulation: Spray-drying, coacervation, or nanoemulsification (using carriers like maltodextrin, cyclodextrins) protects EOs, masks flavor, enhances dispersion, and enables controlled release. Critical for beverages and aqueous systems.

• Active Packaging: Integrating encapsulated EOs or EO vapors into packaging films, sachets, or pads creates a protective atmosphere within the package headspace (e.g., for bread, cheese, fresh-cut produce).

• Emulsification: Creating stable oil-in-water emulsions allows EO incorporation into sauces, marinades, and dressings.

• Vapor Phase Treatment: Using EO vapors in storage rooms or MAP (Modified Atmosphere Packaging) effectively fumigates fruits, vegetables, and grains with minimal sensory impact.

  
  

Benefits and Future Outlook

Plant EOs offer compelling advantages: natural origin meeting "clean-label" demands, broad-spectrum activity, dual functionality (antimicrobial + antioxidant), reduced synthetic chemical residues, lower resistance risk, and sustainability. While challenges remain (sensory impact, regulatory complexity, cost, optimization), the future is promising:

• Synergistic Blends: Combining EOs with each other, mild physical treatments (HPP, UV), or natural antimicrobials (nisin, organic acids) enhances efficacy and reduces needed doses.

• Advanced Delivery Systems: Refining nanoencapsulation and stimuli-responsive release mechanisms.

• Exploring Novel Sources: Identifying potent EOs from underutilized plants or agricultural by-products.

• Sensory & Microbiological Modeling: Predicting optimal doses and impacts in complex food matrices.

• Regulatory Expansion & Cost Reduction: Streamlining approvals and scaling production technologies.