**4. Incorporation of EOs in active packaging system as antimicrobial agent**

Several microorganisms are a threat for food sustainability and human health. They are implicated in quantitative and qualitative food loss [64]. Indeed, in 2011, it was estimated by the Food and Drug Administration (FDA) that 1.3 billion tons of food are annually discarded owing to their contamination by microbial spoilage, contributing to food insecurity and financial losses. Despite the evolution of production and packaging techniques, food contamination by pathogenic microorganisms has remained a persistent global challenge. Currently, there is a growing interest in integrating EOs as antimicrobial agents in food and food packaging [18]. Many previous studies have found that several EOs are efficient against diverse microbes including yeast, bacteria, fungi, and viruses [16, 18, 65].

Some EOs compounds such as aldehydes, phenols and oxygen-containing terpenes especially compound-containing phenol groups are characterized by their potential antibacterial activity [66, 67]. Indeed, phenolic compounds are implicated in the destruction of the bacterial cell membrane and permeability. The hydroxyl groups carried by the phenolic compound are implicated in the inhibition of microorganism enzyme activity. Eugenol and carvacrol are also reported to be potential antimicrobial agents [20].

Previous works showed that antibacterial activity of EOs depends on many factors including the bacterial cell wall composition [68] and cellular shape [65]. Indeed, it was shown that Gram-negative bacteria are more resistant than Gram-positive bacteria to EOs [68]; moreover, rod-shaped bacteria are more susceptible to EOs than cocci [69]. The antibacterial activity of EOs is associated with their lipophilic nature, enabling their accumulation in membranes, and making the membrane their main target [68].

To avoid food deterioration by microbial contamination, antimicrobial agent can be mixed into the initial food formulations, which may affect the taste of the


#### **Table 2.**

*Incorporation of EOs in active packaging system as antimicrobial agent.*

food [70]. Antimicrobial agents, including EOs can be also applied directly by brushing, dipping or spraying on the food surface. Nevertheless, active agent of antimicrobial substances may be evaporated, inactivated or can migrate into the bulk of the foods [71]. Thus, the incorporation of t EO on the packaging film, where they are gradually released to the food surface reducing the contamination and the development of microbial agent, provide better efficiency for foodstuffs preservation. **Table 2** illustrates many recent works published in the last ten years using EOs as antimicrobial agents in active packaging.
