Development of oxygen scavenging packaging with trans-polyoctenamer rubber to enhance the shelf life of walnuts

Given the susceptibility of certain foods to oxidative deterioration, particularly shelled nuts, food science and technology seeks methods to mitigate these processes and extend products’ shelf life. Among the emerging technological approaches, active packaging systems, such as oxygen scavengers, have gained increasing attention. In this study, flexible multilayer structures incorporating two different concentrations (10 and 20 % w/w) of a novel oxygen scavenging polymer—trans-polyoctenamer rubber, TOR—were developed. Since TOR releases volatile compounds after its reaction with oxygen, the developed multilayer structure incorporates the oxygen-scavenging element in one layer sandwiched between layers with volatile-trapping agents (zinc ricinoleate and silica), and shielded by an ethylene–vinyl alcohol copolymer (EVOH) layer acting as an oxygen barrier. The final ten-layer structure films, fabricated by coextrusion lamination under pre-industrial conditions, exhibited good transparency, mechanical strength, excellent barrier properties against oxygen and water vapour (0.61 cc/m² day at 23 °C and 3.18 g/m² day at 38 °C, respectively), and effective oxygen retention capacity (8.0 and 15.2 mL/g for 10 % and 20 % TOR, respectively). These films were applied in the modified atmosphere packaging of walnuts, reducing the headspace oxygen concentration from 3 % to below 0.1 % compared to a similar passive ten-layer structure. The quality evolution of the packaged walnuts was monitored through peroxide index analysis and accumulation of volatile compounds in the bag headspace associated with rancidity and a sensory test. Both parameters indicated that the scavenger improved walnut stability after two months of storage. The sensory test also revealed significant differences between samples. The results demonstrated that the newly developed scavenging structures can effectively enhance the stability of oxygen-sensitive foods.