**5. Industrial applications in agronomy and agrifood industry**

Essential oils are employed in agriculture, medicine, and food industries among others, due to their antimicrobial, antiviral, insecticidal, and antifungal properties. They are specially employed in agriculture, against phytopathogenic fungi such as *Aspergillus, Penicillium, Fusarium, Rhyzoctonia,* and other fungi, which produce many loses in agronomic crops. Also, these fungi are pathogenic to many forest species, and nowadays, we are losing many trees due to these fungi. Essential oils and their effect as antifungal agents must be approached from a biotechnological point, taking in account their genomic, proteomic, and metabolomic functioning. Finally, industrial and commercial applications are being developed, so these products can reach easily their target and have the desired effect for which they are designed. Antimicrobial volatile substances from plants, such as essential oils (EOs) present an alternative to chemical fungicides and food preservatives. Their main new uses and industrial applications of essential oils as antifungals in agronomic crops and in the agrifood industry are the pre- and postharvest treatment of vegetables such as fruits and grains in order to prevent their decay and increase their time of storage, to protect seeds against fungal attack, to prevent food spoilage due to fungal attack, and to produce active containers for vegetables and other food.

Eos are employed to avoid pre- and postharvest fungal diseases of vegetables, but their stability, solubility, and bioavailability are limited and the use of EOs as antifungal agents is limited due to the degrading ability of these volatile compounds under the action of heat, pressure, light, and oxygen. In addition, the fact that there are not water soluble limits their use in certain applications, especially when a controlled release is required [105]. Also, it must be considered that the application of these natural products may alter the characteristics of food, such as aroma or taste, so this is another factor which to be taken in account. The main ways of application of EOs as fungicidal in the agrifood industry, from crops to preservation, are emulsions, encapsulation, and vapor application. All these biotechnologies allow a good contact of the EOs with the plant, a time controlled release, and avoid the alteration of the properties of vegetables. It must be also taken in account that the antifungal effect of the EOs depends on the application method. Suhr and Nielsen [106] have studied how larger phenolic compounds such as thymol and eugenol (from thyme, cinnamon and clove) have best effect against rye bread spoilage when applied directly to the medium, whereas other smaller compounds such as allyl isothiocyanate and citral (from mustard and lemongrass) are most efficient when added as volatiles.

EOs can be prepared into **emulsions** by different techniques. **Microemulsion** of EOs is prepared with EO, Tween 20, and ethanol, and can be unlimitedly diluted with water, being stable for long time. *Laurus nobilis* EO has been proven to be effective in cherry tomatoes applied in this way [107]. **Nanoemulsions** of thymol without carrier oil have also been studied to avoid the deployment of wheat due to *Fusarium gramineum* [108]. **Double w/o/w emulsion** type prepared lipophilic and hydrophilic emulsifiers with xanthan gum as thickener showed stability and water-dilution tolerance and retained most of the electrolytes included in the internal aqueous phase. Antifungal activity of the EOs increased, and the absence of organic solvents makes these formulations environmentally safe. Also, the property of controlled electrolyte release makes these formulations attractive [109].

(*Syzygium aromaticum*), eucalyptus (*Eucalyptus citriodora*), mint (*Mentha spicata*), and savory (*Satureja montana*) with priority components such as eugenol and carvacrol. They also found that each strain of the fungus reacted differently to each treatment, indicating that each strain

Essential oils are employed in agriculture, medicine, and food industries among others, due to their antimicrobial, antiviral, insecticidal, and antifungal properties. They are specially employed in agriculture, against phytopathogenic fungi such as *Aspergillus, Penicillium, Fusarium, Rhyzoctonia,* and other fungi, which produce many loses in agronomic crops. Also, these fungi are pathogenic to many forest species, and nowadays, we are losing many trees due to these fungi. Essential oils and their effect as antifungal agents must be approached from a biotechnological point, taking in account their genomic, proteomic, and metabolomic functioning. Finally, industrial and commercial applications are being developed, so these products can reach easily their target and have the desired effect for which they are designed. Antimicrobial volatile substances from plants, such as essential oils (EOs) present an alternative to chemical fungicides and food preservatives. Their main new uses and industrial applications of essential oils as antifungals in agronomic crops and in the agrifood industry are the pre- and postharvest treatment of vegetables such as fruits and grains in order to prevent their decay and increase their time of storage, to protect seeds against fungal attack, to prevent food spoilage due to fungal attack, and to produce active containers for vegetables

Eos are employed to avoid pre- and postharvest fungal diseases of vegetables, but their stability, solubility, and bioavailability are limited and the use of EOs as antifungal agents is limited due to the degrading ability of these volatile compounds under the action of heat, pressure, light, and oxygen. In addition, the fact that there are not water soluble limits their use in certain applications, especially when a controlled release is required [105]. Also, it must be considered that the application of these natural products may alter the characteristics of food, such as aroma or taste, so this is another factor which to be taken in account. The main ways of application of EOs as fungicidal in the agrifood industry, from crops to preservation, are emulsions, encapsulation, and vapor application. All these biotechnologies allow a good contact of the EOs with the plant, a time controlled release, and avoid the alteration of the properties of vegetables. It must be also taken in account that the antifungal effect of the EOs depends on the application method. Suhr and Nielsen [106] have studied how larger phenolic compounds such as thymol and eugenol (from thyme, cinnamon and clove) have best effect against rye bread spoilage when applied directly to the medium, whereas other smaller compounds such as allyl isothiocyanate and citral (from mustard and lemongrass) are most

EOs can be prepared into **emulsions** by different techniques. **Microemulsion** of EOs is prepared with EO, Tween 20, and ethanol, and can be unlimitedly diluted with water, being stable

**5. Industrial applications in agronomy and agrifood industry**

of the pathogen had different survival mechanisms.

and other food.

154 Potential of Essential Oils

efficient when added as volatiles.

The **microencapsulation** in porous materials allows direct contact between the fungus and the microparticle in the soil, which acts more efficiently against the fungus. That is, these could be put directly into the crop acting as biopesticides throughout the growth of the vegetables. Microencapsulation can be done by simple coacervation [110–111] and it has been tried already in fruits such as mango with thyme and rosemary EOs [110] and to preserve peanut seeds with *Lippia turbinata* EO [111]. Carvacrol and thymol from oregano and thyme have also been studied in microcapsules of mesoporous silica and B-cyclodextrin, together with cinnamaldehyde and eugenol from cinnamon and clove, respectively. **Nanoencapsulation** is also used to enhance antifungal activity and stability of the oils against fungi. Nanoencapsulation in chitosan nanoparticles (CSNPs) is done by an ionic gelation technique. This technique has shown a controlled and sustained release of EOs for 40 days in comparison with unmodified EOs [101]. Nanoparticle carriers of EOs, as compared to microsize carriers, show a better surface area rate, solubility, bioavailability, controlled release, and targeting of the ingredients [101]. Nanoencapsulation of EOs has been studied also for their incorporation into fruit juices to prevent fungal activity while not affecting on the quality attributes of the product [112].

**Simple vapor application** of EOs can change the sensory profile of fruits and vegetable [113–114]. EOs from cinnamon (*Cinnamomum zeylanicum* Nees.), thyme (*Thymus vulgaris* L.), oregano (*Origanum vulgare* L.), clove (*Syzygium aromaticum* L.), lemongrass (*Cymbopogon citratus* [DC] Stapf.), and ginger (*Zingiber officinale* Rosc.) have shown to inhibit the growth of Aspergillus spp. in oats [114]. But furthermore, there are new technologies of application of the EOs, such as the combination with **warm air flow (WAF)**, that can be used in the control of postharvest fungal pathogens of grains [115], being more effective compared to standard vapors in disc volatilization [113] with very low effect on their sensory profile.

EOs are a very good source of natural additives for **active packaging (films & coatings)**, which refers to the incorporation of additives into the packaging material, maintaining its properties without adding active agents in the food product, thus reducing the use of aggressive techniques and synthetic chemicals in food. Oregano is one of the EOs that has been positively tested in this way [116]. In that sense, chitosan **composite films** enriched with essential oils of cinnamon, thyme, clove, and lime alone or in combination have been tried against *Colletotrichum gloeosporioides* in papaya fruit. This coating can be an alternative to potentially reduce the need for cold storage during postharvest handling [117]. Edible coatings with oregano EO have been proved for the preservation of tomatoes against *Alternaria alternata* growth maintaining the sensorial acceptability of tomatoes [118].
