**1. Introduction**

Oxidation processes and microbial growth are common causes of food deterioration which result in color changes, texture modifications, development of off-flavor, and loss of nutritional value and quality of foodstuffs [1,2]. In this regard, spices and herbs have been traditionally added to food, not just as flavoring and healing agents, but also as preservatives [3]. Nowadays, many spices and herbs are recognized as sources of bioactive compounds which are able to stabilize free radicals and prevent oxidation processes and/or act as bacteriostatic or bactericidal agents [2,3]. In addition, there is a growing interest from consumers and the food industry for the use of natural active compounds in food preservation due to their synergy, potency, and presumed low side effects when compared to synthetic additives [4]. However, a major drawback for direct food application of extracted active compounds represents their susceptibility to adverse external factors, chemical instability, and interactions with food constituents [5]. Another limiting factor is a rapid actuation and diffusion of active compounds within the bulk of food [6,7]. A promising approach to overcome these problems is the incorporation of active compounds in a polymeric matrix by encapsulation, to provide stability, keep functionality, and increase effectiveness during time, creating a physical barrier between actives and their environment [8].

Many efforts done to prevent food deterioration and achieve higher effectiveness of active compounds have triggered innovations in food packaging. This current trend is reflected in the development of active food packaging with improved functionality. In this context, the passive role of traditional packaging in protecting and marketing of a food product has evolved into a novel function as a carrier of active compounds [9,10]. This novel concept is based on the incorporation of various active agents into a packaging material with the aim to maintain or enhance quality and safety, extend shelf life of a packaged product, and to reduce the packaging related environmental pollution [10,11]. Nowadays, the use of natural active compounds as functional ingredients in active food packaging is highlighted.

Sage (*Salvia officinalis* L.) is a herb widely used in cookery due to its seasoning and flavoring properties as well as in traditional medicine to treat dyspepsia, excessive sweating, age-related cognitive disorders, and throat and skin inflammations [12]. Moreover, sage is one of the herbs with a grea<sup>t</sup> potential for use as a functional ingredient for the development of active food packaging due to its well-known antioxidant [13,14], antibacterial [3], and antifungal [14] effects. These beneficial activities are positively related to phenolic compounds [3,14], such as phenolic diterpenoids (carnosic acid, carnosol, rosmanol), phenolic acids (caffeic acid, rosmarinic acid, ferulic acid) and flavonoids (luteolin derivatives, apigenin derivatives), among others [13–15]. Essential oils and extracts of *Salvia officinalis* are generally recognized as safe according to the U.S. Food and Drug Administration [16].

While formulating active food packaging, an environmental issue related to an increasing quantity of disposed plastic packaging with unknown biodegradation time should be taken into account. This problem has set a strong challenge towards replacement of non-biodegradable polymers by biodegradable ones, especially for single-use plastic items [17]. In this sense, poly(ε-caprolactone) (PCL), a commercially available and biodegradable aliphatic polyester, could represent an alternative. It is a hydrophobic, semi-crystalline polymer with a low melting point and is miscible with many other polymers [18,19]. The rheological and viscoelastic properties allow an easy processability of PCL [18]. This material is very interesting for packaging applications [19], as well as being used as a carrier of active compounds and development of active materials. For instance, Martínez-Abad et al. studied the potential of PCL for preparation of antibacterial solvent casted films containing cinnamaldehyde and allyl isothiocyanate [20]. Also, PCL electrospun fibers loaded with nettle extract and embedded to whey protein isolate were successfully applied as a bioactive coating to inhibit bacterial growth and extend quality of fresh fish fillets [21].

The design of active packaging materials represents a very dynamic field and a real challenge [10]. In this regard, the electrospinning technique supposes an innovative nanofabrication approach for the development of active food packaging coating and interlayer materials. This approach employs a high-voltage electric field imposed on a polymer solution to create ultrathin mats composed of polymeric fibers with diameters in micro, submicro, and nano range [22–24]. Because of a high trapping efficiency and no need for high processing temperatures, the electrospinning technique is very suitable for entrapping active compounds, such as antioxidants [24] and antimicrobials [25] within a fibrous polymer matrix [22]. Fiber-based systems have gained a lot of attention as a way to improve active functionality and achieve an optimal effect during the food storage [6]. Also, characteristics such as cost-effectiveness, continuous fabricating capability, and a facile operating process make the electrospinning technique an excellent candidate for the development of active packaging materials [22].

There are some studies on the incorporation of sage extracts into whey protein isolate [26] and chitosan matrix [2] by means of solvent casting technique. The study on the whey protein isolate-based film has proven that there is grea<sup>t</sup> potential of sage extract to be used as the active constituent of food packaging for antioxidant protection of meat products. Nevertheless, there was no information on film properties [26]. On the other hand, the chitosan-based film loaded with sage extract has been evaluated with respect to its physical properties, regardless of its active functionality [2]. Despite those research works, according to our knowledge there is no commercial application of sage extract in commercial food packaging. When compared to casted films, electrospun films would provide more desirable properties, such as homogeneous dispersion of film constituents and better solvent resistance [27]. However, to the best of our knowledge, the use of the electrospinning technique to develop a PCL-sage extract system has not been carried out so far.

The main aim of this study was to develop and characterize active PCL-based films loaded with sage extract. Formulations containing different sage extract loadings were prepared, employing the electrospinning technique followed by annealing treatment. A comprehensive investigation was performed to assess the effect of the sage extract addition on morphology, transparency, hydrophobicity, thermal stability, tensile properties, water vapor and aroma barrier performance, and, most importantly, on antioxidant and antimicrobial activities of the films.

#### **2. Materials and Methods**
