## 5 Natural Methods
### Essentials Oils  
Essential oils are a promising alternative, having antimicrobial and antioxidant effects and being able to extend the shelf life of foods. However, the problems related to the low solubility in water, limited stability, and strong aroma of some essential oils can represent a disadvantage in certain food products. To overcome these limitations, oils can be integrated into edible and biodegradable films, which allow a controlled release of active compounds to create smart or active packaging. These represent innovative solutions that interact with the food atmosphere, allowing a more efficient preservation of food products. In addition, various modern technologies, such as hydrogels, nanoemulsions, and nanoparticles, are applied to improve the delivery of oils and protect foods against microbial contamination [136; 137; 138]. Also, microencapsulation of essential oils in a protective matrix, such as aloe vera or inulin, can improve the stability and antimicrobial and antioxidant efficacy of these oils during storage [139; 140]. Natural methods and chemical agents used to reduce the incidence of _L. monocytogenes_ in dairy products are presented in Figure 2.  
In the food industry, essential oils are regulated and generally recognized as safe (GRAS), which has contributed to the growing interest in their use in food preservation. Although they are effective against bacteria and other microorganisms, the high concentrations required to ensure preservation can negatively influence the sensory properties of the products. Therefore, current research is focused on developing techniques  
Figure 2: Natural methods and chemical agents used to reduce the incidence of _L. monocytogenes_ in dairy products. that allow the use of essential oils at lower concentrations without compromising their antimicrobial efficacy [141; 142]. Essential oils are volatile secondary metabolites extracted from various parts of plants, such as fruits, seeds, flowers, leaves, bark, and roots. They are bioactive components of spices and are formed by a complex mixture of volatile and non-volatile compounds, with a concentration ranging from 1% to 17%. Essential oils are mainly extracted from plants in the families _Poaceae_, _Lantiaceae_, _Pinaceae_, _Rutaceae_, _Asteraceae_, _Lauraceae_, _Apiaceae_, _Piperaceae_, _Angiosperms_, _Sapindaceae_, and _Mytaceae_, among many others [143]. Essential oils are generally lipophilic and can be classified into various categories, such as monoterpenes, phenolic acids, alkaloids, flavonoids, carotenoids, and aldehydes. Their antimicrobial activities have been documented, including those of essential oils obtained from cinnamon, anise, dill, cloves, oregano, and zedoary. Synergistic effects of mixtures of these oils in combating microorganisms have also been reported [144]. The composition of essential oils varies depending on the part of the plant from which they are extracted by various methods, such as steam distillation, mechanical processing, or solvent extraction, and are composed of mixtures of phenylpropenes, terpen, and other volatile compounds with strong antimicrobial and antioxidant properties. They can penetrate the bacterial membrane, inhibiting their essential functions [145]. For example, terpen are known for their action against bacteria, viruses, and fungi. Currently, approximately 3000 essential oils are known, and some of them are commercially important, being used in the agronomic, cosmetic, chemical, perfume, pharmaceutical, and food industries due to their potential bioactivities [146]. Essential oils have the ability to act synergistically; that is, combining several essential oils can enhance antimicrobial activity, thus reducing the need for synthetic agents. These oils work by disrupting the cell membrane of microorganisms, making them effective against bacteria. Gram-positive bacteria are more susceptible to essential oils due to their cellular structure, while Gram-negative bacteria are more resistant [147].