## 5 Natural Methods
### Plant Extract  
Plant extracts are derived from various parts of plants: leaves, flowers, roots, or seeds. Extraction methods vary, including cold pressing, steam distillation, hydrodistillation, supercritical CO\({}_{2}\) extraction, and the use of organic solvents. These methods influence the chemical composition and biological effects of the extracts [156]. Plant extracts and essential oils are effective against Gram-negative and Gram-positive bacteria and are increasingly being studied for their use in the food industry. In particular, essential oils from spices such as pepper, ginger, garlic, and onion have demonstrated antimicrobial and antifungal activities, making them promising candidates for the development of new natural antimicrobial agents [145]. Plants of the genus _Thymus_, used both in traditional medicine and as spices, have been studied for their antimicrobial potential. _Thymus zygis_ has shown broad antimicrobial activity, indicating great potential for food preservation [145]. In parallel, the use of synthetic compounds such as aromatic hydrocarbons, benzimidazoles, and synthetic antioxidants (BHA, BHT) raises concerns about long-term food safety due to potential carcinogenic effects. In response, consumers prefer natural additives, and plant products are becoming viable alternatives to synthetic preservatives. Essential oils and plant extracts offer promising solutions for extending the shelf life of perishable foods, especially in the case of fresh, minimally processed, or ready-to-eat products. Plant antimicrobials are composed of secondary metabolites, such as phenolic compounds, terpen, and alkaloids, which act on microbial cells. Although plant antimicrobials are effective, their use in the food industry is limited by chemical instability, low dispersibility, and flavor issues. In this context, various stabilization techniques, such as nano-emulsions and encapsulation, improve the activity and controlled release of antimicrobial compounds during food storage. A great diversity of structures among plant secondary metabolites (PSM) occurs in nature (e.g., over 12,000 known alkaloids, over 10,000 phenolic compounds, and over 25,000 different terpenoids). Structurally, plant antimicrobials can be divided into two classes: PSMs with one or more nitrogen atoms in their structures, such as alkaloids and glucosinolates, and PSMs without nitrogen, such as terpenoids and phenolics. Alkaloids, glucosinolates, and phenolics are water-soluble compounds, while terpenoids are lipophilic PSMs [134]. The use of garlic extract encapsulated in nanoliposomes showed increased efficacy against _Listeria_ spp. in milk, significantly reducing the number of viable cells after a few hours of incubation. Co-encapsulation of garlic extract with nisin further improved their efficacy, with significantly better results in reducing the population of _L. monocytogenes_, _S. aureus_, _Salmonella_, and _E. coli_ in milk. This technique was also effective at low temperatures, maintaining a significant reduction in pathogenic bacteria for up to 25 days. Extracts of cinnamon, garlic, rosemary, and oregano have been shown to be effective in inhibiting _L. monocytogenes_ in various types of cheese. Plant extracts and essential oils are well-received in the dairy industry, contributing to the improvement of flavors and antioxidant and antibacterial properties. They can be added in free or encapsulated form to protect the active compounds and control their release. Plant extracts and essential oils can also support the survival of probiotics and inhibit pathogenic microorganisms, increasing the value of dairy foods [157]. Natural fruit preservatives, such as citrus or apple peel extracts, have been used to prevent spoilage of milk and dairy products, demonstrating efficacy against lipid oxidation and microbial growth. For example, apple peel extracts added to yogurt improved its properties without negatively affecting pH or syneresis.