## 2 Challenges in Food Supply Chains Related to Packaging Characteristics  
### Current Packaging Characteristics  
While bio-based systems are the focus of the review, we begin by discussing general issues of packaging and the reasons behind the current ubiquitousness of fossil-based food packaging. Intensive research and development efforts over a long period of time resulted in packaging solutions which are optimized with regard to various important parameters that guarantee their functionality including material weight per unit of packed volume [8; 36], mechanical characteristics (impact and tear strength, stiffness, flexibility), durability, and many others [2; 5; 9; 17; 37; 38]. Moreover, fossil-based plastics are less expensive per weight unit compared to most of the bio-based materials. Therefore, currently, alternative bio-based materials are more expensive because of poor commercial availability and lack of efficient production processes. In the future, the prices for fossil resources will rise due to the limited availability, and on the other hand, costs for bio-based plastics may drop due to improvements in production process efficiency [39]. The current focus of research activities is the reduction of packaging waste especially fossil-based material [5]. LCA showed that a reduction in environmental impact of the packaging itself can be best achieved by minimization of used materials (thinner layers) that retain mechanical and barrier properties rather than emphasizing end-of-life issues (such as recycling or disposal) [7]. Today, multi-layer materials are widely used for food packaging throughout the food industry. As multi-layers of plastic can be easily adjusted to the various requirements of different food types, this kind of packaging can offer effective solutions to maintain food safety and quality, achieve optimal shelf life, and minimize food waste [8]. Although from an environmental, sustainability, and biocompatibility perspective, the use of multi-layered packaging materials has to be reduced, their global use for food applications is growing. This development is based on the mechanical and barrier properties of multi-layer materials (higher resistance to water, gas, and aroma transfer) [1; 7; 8]. Especially, the barrier against oxygen is a key factor for food quality and safety [7]. According to [PERSON], appearance, color, lipid stability, nutritive value, and palatability (texture, flavor, aroma) are significant factors that must be considered when choosing a packaging solution [40]. Changing to biobased packaging materials, these factors have to be considered to ensure the shelf life and quality of the food [41; 42]. So far, a broad variety of bio-based materials have been investigated to meet the purpose and achieve the properties of commercial packaging plastics. Although many new materials are used, companies worry about their physical inferiority compared to conventional polymers. Currently, European legislation and regulations are forcing companies to eliminate or reduce conventional plastic in packaging (COM/2018/028 final) [8]. Even if there is a desire to change, there is a conflicting pressure that prohibits changes in packaging because of different attitudes along the supply chain. The companies are faced with a challenge of alternatives offering higher costs and lower functionality, existing infrastructure, and inconsistent legislation [43; 44]. Today, many companies are trying to use materials that are more recyclable instead of using bio-based materials. According to the adopted \"European strategy for plastics in a circular economy\" (COM/2018/028 final) where sustainability is the underlying motivation, recycling of plastic packaging is a key factor [8]. Recycling is viewed as the primary mechanism to reduce the environmental and waste management issues that are related especially to the use of conventional plastic [45]. Therefore, sorting and recycling capacities have to be expanded and modernized.