The development of iron-based oxygen absorbing systems used in food packaging and preservation

The use of active packaging gives added protection to foods and provides extended shelf life. One of the most used active packaging techniques is oxygen absorbing systems composed of iron powder. The overall objective of this research was to develop iron-based oxygen absorbing plastic films that could extend the shelf life of oxygen sensitive foods. To achieve the objective, the effectiveness of current commercial iron-based oxygen absorbing sachets to retard lipid oxidation was compared to other methods (antioxidants, surface area reduction and nitrogen flushing). Next, the oxygen absorption kinetics of powdered iron containing NaCl as a catalyst were optimized using response surface methodology (RSM) at different temperatures and relative humidities. Finally, oxygen absorbing plastic films were developed and their oxygen absorption kinetics determined. Menhaden oil was used as a model system to evaluate different methods to retard lipid oxidation. Lipid oxidation was measured mainly by thiobarbituric acid (TBA) analysis. Oxygen absorption of powdered iron and plastic films containing iron-based compounds was measured by a constant volume manometric method. Oxygen absorbing sachets prevented the oxidation of menhaden oil and thus proved to be the most effective method. The sachets were also the easiest and quickest method to use. RSM analysis for oxygen absorption by powdered iron predicted a maximum rate of 6.54% O2/hr at 56°C, 78% relative humidity and 0.8% NaCl. Activation energies determined for this oxygen absorption were lower than those of relevant food deteriorative reactions (lipid oxidation and nutrient loss). Therefore, powdered iron will protect food from oxidative deteriorative reactions. Plastic films made from low density polyethylene (LDPE) containing iron-based oxygen absorbers effectively absorbed oxygen at significant rates to be useful in food packaging. The minimum surface areas determined to absorb ambient oxygen levels (20.9%) in one day varied from 490 to 730 cm2 for films 228.6 to 76.2 μm thick, respectively. However, less surface area was needed to absorb ambient oxygen levels over two days, 300 to 440 cm 2 for films 228.6 to 76.2 μm thick, respectively. Overall, oxygen absorbing systems are very useful to retard oxidative reactions in packaged foods. These systems were shown to remain active when incorporated into plastic films. Therefore, active packages made from these films will provide extended shelf life for many foods.