# Chitosan Films with Caffeine and Propolis as Promising and Ecofriendly Packaging Materials
## 1 Introduction  
Nowadays, plastics are materials commonly used in the packaging sector. This can be attributed to their easy accessibility, affordability, and exceptional longevity. Unfortunately, the durability of plastics does not necessarily yield positive results. A substantial time investment is necessary to break them down, which is a serious problem if they are not properly disposed of. Due to the observed degradation of the environment associated with excessive consumption and the increase in consumer awareness, the packaging industry is facing the challenge of finding appropriate materials that could replace plastics. This challenge is being addressed by the quest for new, natural and biodegradable materials that will be ecofriendly, while, like plastics, being noted for their advantageous mechanicalor optical properties. In addition, these materials, through the use of appropriate additives, can ensure the preservation of high quality and freshness of packaged products [1; 2]. The initial purpose of food packaging is to safeguard the enclosed food while it is being transported or stored. Moreover, it is important for the packaging to shield the packaged food from the detrimental impact of external factors such as UV radiation and to exhibit appropriate mechanical or barrier properties. Packaging serves the essential purpose of maximizing the lifespan of food products, preserving their quality, and protecting them from external factors that could accelerate spoilage or compromise their nutritional properties [3]. The greatest food losses during production and transport are caused by microbial transformations. One way to protect finished food products from negative external influences is packaging. However, traditional packaging does not guarantee that food will be durable and fully safe for consumers. This is because many products succumb to microbial contamination during or even after the final stages of production. In such cases, protecting food with traditional packaging is insufficient. This is because a number of undesirable microorganisms, both pathogenic and spoilage-causing, can thrive in contaminated products packaged in traditional packaging. These include pathogenic strains of the genus _Listeria_, _Pseudomonas_, _Salmonella_, _Clostridium_, _Brochtotrix_ and psychrophilic molds, among others [4; 5]. Reducing the growth of these microorganisms is possible by replacing traditional packaging, or the so-called passive packaging, with active packaging. One form of active packaging that is attracting increasing interest from consumers and food manufacturers is active antimicrobial packaging. Such packaging can be produced with components that exhibit natural activity, such as, e.g., chitosan, or gain such activity following their physical or chemical modification. Many chemical compounds have proven to be agents through which antimicrobial activity can be imparted to packaging [5]. Packaging materials that are both natural and biodegradable are typically composed of film-forming substances, commonly from proteins, polysaccharides, lipids, and resins, either individually or as composite materials [1; 5]. Studies have shown that chitosan is an effective packaging material because it is a biodegradable natural polymer. Chitosan is a polysaccharide that offers various advantages, including lack of toxicity, biocompatibility and ability to break down naturally. Derived from the shells of crustaceans, which are a byproduct of the seafood industry [6]. This versatile material finds applications in several industries, including medicine, agriculture, textiles, food, and environmental protection [7; 8]. Also, chitosan exhibits great potential as a biopolymer used for the production of functional and natural packaging [9; 10; 11]. Therefore, it holds significant promise as a suitable choice for serving as a base material in natural and biodegradable composite materials, thanks to its multitude of advantageous characteristics.