Prediction equations for gases in flexible modified-atmosphere packages of respiring produce are different than those for rigid packages

Total pressure generally decreases in a sealed rigid package containing respiring produce, whereas total pressure is essentially constant and free volume decreases in a flexible package. We found that predicted O-2, CO2, and N-2 partial pressures were different for similarly designed (same surface area, thickness, film permeabilities and produce mass) flexible and rigid packages at ''quasi steady state'' and steady stale, respectively. Predicted O-2 and CO2 partial pressures were slightly higher in a flexible package than in a rigid package and were a function of the film permeability ratio of N-2 to O-2 and of CO2 to O-2. They also related to the ratio of product CO2 production rate to O-2 uptake rate, target steady-state O-2 partial pressure, and respiration characteristics. Differences were slight for films such as low-density polyethylene.