## 4 Discussion  
The primary function of food packaging is to protect food from external contamination, with the aim of both improving its shelf life and ensuring its safety for the consumer. During the last few years, the changing demands of the market have induced food industries to direct their research towards innovative and sustainable technologies of food preservation. Active food packaging is the most innovative system of interaction between packaging and food, capable of extending its shelf-life and increasing the quality, safety and organoleptic characteristics during the storage period. The development of technological innovations in the agri-food field to expand the \"life\" of perishable foods, however, have not prevented the increased incidence of bacteria with high adaptability to survive in adverse environmental conditions. The most relevant pathogens are those endowed with psychotrophic characteristics, able to survive and even multiply at temperatures close to zero. Among the psychotrophic bacteria, _L. monocytogenes_ appears to be the main human food-borne pathogen abundantly widespread in nature and isolated from a wide variety of foods. The data obtained in the present investigation can represent an important step forward in the control of _L. monocytogenes_ in foods that require storage at refrigeration temperature, notably perishable products such as seafood. All the EOs employed in the study confirmed their anti-_L. monocytogenes_ activity in the \"in vitro\" studies, even when incorporated into the coatings. The coating matrix has been found to be suitable for its use in the food field, allowing a gradual release of the EOs on packaged food, thereby sustaining a marked antibacterial activity during preservation at refrigeration temperature. At the same time, the EOs have shown to act synergistically even when incorporated into the coating, and the significant reduction in the amount of EOs (10-20 times) needing to be employed against _L. monocytogenes_ overcomes the problem of their limited use due to the undesirable organoleptic impact when added to foods in high concentration [49; 50; 51]. Hence, the inclusion of the EOs within the coating not only ensures the anti-_Listeria_ activity, increasing the shelf-life of the food products, but it also mitigates the strong smell of EOs, improving the sensory properties of the food, as already reported [45]. These results have also shown the capability of the bacteriocin bacLP17 to maintain unaltered antibacterial activity against _L. monocytogenes_ inside the coatings, with a gradual release from coating to food. Among active packaging applications, the incorporation and subsequent slow release of antimicrobials is receiving much attention as a means to extend the bacterial lag phase and slow down the growth of microorganisms to  
Figure 3: Coating together with bacLP17 (**a**) and with the best combination bacLP17/EOs: bacLP17/_Citrus lemon_ (**b**), bacLP17/_M. pipertia_ (**c**), bacLP17/_M. pipertia_/_T. vulgaris_ (**d**), applied on artificially contaminated shrimp samples. Experiments were performed in triplicate _p_-values of ¡ 0.05 (*), \(p\) ¡ 0.01 (**), \(p\) ¡ 0.001 (***) and \(p\) ¡ 0.0001 (****) were considered significant by _t_-test and ANOVA. maintain food quality and safety over time [52; 53; 54]. The combined use, inside an edible coating, of antimicrobial natural substances of different origin and endowed with peculiar characteristics can overcome some of the drawbacks associated with the use of chemical additives, as well as some limitations due to features of EOs and bacLP17, namely that bacterios are not usually characterized by a broad host range, and the use of EOs is often limited by undesirable organoleptic impact.