14A-31

Oxygen absorption kinetics of O2 scavengers

G. Tewari1, D. S. JAYAS1, R. A. Holley2, and L. E. Jeremiah3. (1) Biosystems Engineering, University of Manitoba, Winnipeg, MB R3T 5V6, Canada, (2) Food Science, University of Manitoba, Winnipeg, R3T2N2, Canada, (3) Meat Research, Agriculture and Agri-Food Canada, Lacombe, AB T4L 1W1, Canada

Commercial O2 scavengers are designed to remove a specified amount of O2 from a typically high O2 atmosphere without consideration of their O2 absorption rates. For meats packaged in 100% CO2 or N2, small amounts of O2 are left around the meat. This can cause transient and/or permanent meat discoloration. To eliminate O2, scavengers can be used but there is little information on their absorption rates at low O2 concentrations.

Therefore, the O2 absorption kinetics of six commercial O2 scavengers were characterized at low O2 concentrations.

O2 scavengers were placed in impermeable bags, which were either filled with: 240 mL air (20% O2); 4.5 L N2 plus 15 mL air (500 ppm O2); or 3.5 L CO2 plus 9 mL air (500 ppm O2). The O2 concentration in the bags was determined every hour for 8 h using an O2 analyzer. Variability among individual scavengers was characterized and effects of temperature (25, 12, 2, -1.5°C), initial O2 concentration after sealing (20% and 500 ppm), and scavengers in simulated master pack systems, on the O2 absorption rate were quantified. The order of O2 absorption reactions was then determined.

The O2 half-lives among O2 scavengers of the same type differed by 2 h. Low temperature use gave 7 times longer O2 half-lives than use at high temperatures. Up to 5 times shorter O2 half-lives were obtained with an initial concentration of 20% O2 when compared with 500 ppm O2. Scavengers in simulated master pack systems had up to 4 times longer O2 half-lives than scavengers placed directly in bags. The O2 absorption reactions were of first order for both initial O2 concentrations.

These results suggest rapid removal of O2 is possible, provided multiple O2 scavengers are used in closed packages. However, the number should be based on scavenger type, desired rate of O2 removal, storage temperature, pack atmosphere (air/N2/CO2), and initial O2 concentration.