# Rosehip Seed Oil-Incorporated Chitosan Films for Potential Fruit Packaging Applications
## 1 Introduction  
In recent years, a tendency to replace plastic packaging with environmentally friendly, edible, and biodegradable films using natural resources has been observed [1]. This shift is primarily driven by concerns about environmental pollution caused by plastic packaging and the desire to minimize food waste. Plastic pollution has become a pressing global issue, prompting governments, businesses, and consumers to seek alternative packaging solutions that are more sustainable [2]. Edible films are thin layers of edible material derived from sources such as polysaccharides, proteins, or lipids [3, 4]. These films can be formulated to have properties similar to traditional plastic packaging, such as barrier properties and mechanical strength, while being edible and biodegradable. In addition, they have the advantage of containing various biologically active substances, such as coloring agents, antimicrobial agents, and antioxidants [5]. Chitosan stands out as a highly promising biomaterial for substituting synthetic counterparts, especially in the realm of food and packaging applications [6, 7]. It is characterizedas a linear polysaccharide composed of (1,4)-linked 2-amino-deoxy-\(\beta\)-D-glucan. Commercially, chitosan is obtained through the chemical alkali deacetylation process of chitin, which ranks as the second most abundant polysaccharide in nature, following cellulose [8]. Chitosan has some advantages over other biomaterials because of its antimicrobial activity against a wide variety of microorganisms including fungi, algae, and some bacteria [7]. One common theory about the way in which chitosan exhibits antibacterial activity suggests that the positively charged amine group in chitosan binds to the negatively charged bacterial cell wall, affecting membrane permeability and disrupting normal cell function. Chitosan may also act as a chelating agent, binding to metal elements and inhibiting toxin production and microbial growth. Another proposed mechanism involves lower molecular weight chitosan entering the bacterial cell and binding to DNA, preventing DNA replication and causing cell death [8]. Another well-known function of chitosan is its antioxidant activity. Chitosan can scavenge the excessive free radicals due to the presence of functional amino and hydroxyl groups on its backbone [9]. Chitosan is reported to present radical scavenging activity, including OH\(\bullet\), O2\(\leftarrow\), DPPH\(\bullet\), and ABTS\(\bullet\)+. The scavenging of these radicals is negatively correlated with the degree of acetylation (DA) of chitosan due to the stabilization of oxidized structures provided by the amino group. Based on [PERSON] et al., native chitosan (MW = 307 kDa, DDA = 80%) had a scavenging ability against the DPPH radical (9.4%) [10]. Similar to many polysaccharide-based films, chitosan films possess a strong hydrophilic nature, granting them favorable barrier properties against gases and lipids but presenting a challenge in terms of water vapor permeability [11]. This limitation restricts the potential applications of chitosan films, as effective moisture control is often essential in food packaging scenarios [12]. The addition of essential oils (EOs) to chitosan films can lead to an improvement in both their antibacterial activity and water-resistant properties [13]. They are a promising alternative to conventional antimicrobials in food packaging applications due to their ability to sterilize headspace and food surfaces [14]. They are approved by the FDA and are generally recognized as safe [15]. Moreover, incorporating EOs can influence the mechanical, barrier, and thermal properties of the final composite, potentially improving their antimicrobial properties [16]. For instance, EOs can reduce the water vapor permeability (WVP) of hydrophilic materials, decrease tensile strength (TS), and increase elongation at break.