Zein/chitosan/cellulose nanocrystal based active food contact layer: Unlocking the interrelations between release behavior, mechanical stability, and hydrolysis

Abstract

Disposing food and fossil-based packaging waste is currently a huge global challenge. Bio-based active food packaging is potentially an efficient and versatile approach to reducing household and retailer waste. Active compounds released from packaging could increase food shelf-life. Compound release behavior depends on the physical and mechanical durability and strength of the active layer in contact with food. Bio-based polymers are weaker and more prone to hydrolytic degradation than fossil-fuel-derived polymers. In this study, the structure-properties relationships of mechanically and hydrolytically robust and durable bio-based zein/chitosan films with cellulose nanocrystal (CNC) filler network, containing different combinations of active compounds, were investigated pertaining to their role as a food contact layer. Different essential oils (EOs), namely thyme (TEO EO) and oregano (OEO EO), and their complex with the phenolic thymol (THY) were investigated as active compounds. EOs worked synergistically with the phenolic THY to increase the mechanical strength and durability of active film layers. The CNC-incorporated active film layers with TEO EO and OEO EO had higher mechanical strength and greater hydrolytic stability compared to non-CNC-included films, which allowed films to remain in contact with food for longer. EO addition substantially enhanced the gas barrier performance of films, and no further improvement was observed with the addition of CNC. EOs/CNC also imparted films with antimicrobial activity in vitro. This paper provides insights into how to design filler network-based active food packaging layers, with regards to which combination of active compounds and fillers are required for different food packaging applications.