Different strategies to reinforce the milk protein-based packaging composites

Background: The increase in environmental concerns and the severe energy depletion as a result of using petroleum-based polymers have led to the introduction of biopolymers such as milk proteins as a hot topic due to their biodegradability, biocompatibility, and renewability. Scope and approach: In the current review, we first discuss packaging composites based on milk proteins and their structural challenges. Then an overview of different functional and structural reinforcement methods, such as loading natural bioactive compounds, nanofillers, cross-linking agents, and plasticizers for milk protein-based packaging composites, is reported. The potential applications in the food packaging sector are discussed as well. Key findings and conclusions: Milk-based proteins are considered as valuable biopolymers with suitable thermal stability, non-toxicity, preventing moisture and flavors losses, exceptional functionalities due to their unique structure, and excellent gas barrier attributes. However, their limitations (moisture sensitivity, brittleness, low elasticity, etc.) should be addressed prior to further industrial applications to fill the gap between them and synthetic polymers. The main drawbacks of milk protein-based packaging systems can be modified by applying bioactive compounds, nanofillers, cross-linkers, plasticizers, etc. In conclusion, the modified milk protein-based biopolymers could be introduced as promising alternatives to petroleum-based polymers. However, selecting the correct milk protein source in addition to appropriate reinforcing agents and procedures based on food nature could guarantee a well-protected food with extended shelf-life and the least environmental impacts.