Modelling the effect of super‐atmospheric oxygen and carbon dioxide concentrations on the respiration of fresh‐cut butterhead lettuce

Abstract For the design of high oxygen modified atmosphere packages, knowledge and modelling of respiration rates at both low and super‐atmospheric oxygen levels is required. Fresh‐cut butterhead lettuce was stored in glass jars at three different temperatures (1 °C, 5 °C and 9 °C), three carbon dioxide levels (0, 10 and 20 kPa) and eight different levels of oxygen partial pressures (0, 2, 5, 10, 20, 50, 70 and 100 kPa). Oxygen consumption and carbon dioxide production rates were measured. The respiration rates were significantly reduced by low temperatures and elevated carbon dioxide concentrations up to 10 kPa. At carbon dioxide concentrations of 20 kPa the respiration rates were comparable to those at 0 kPa CO 2 probably due to an injury response. Oxygen concentrations had to be below 2 kPa to significantly reduce the respiration rates compared to air conditions. Respiration rates were also slightly lower under super‐atmospheric (50, 70 and 100 kPa) oxygen partial pressures than at air conditions. Additionally, a Michaelis–Menten based model to describe the respiration rates as a function of oxygen, carbon dioxide and temperature was constructed. Models that include respiration rates at super‐atmospheric oxygen levels have not previously been described. The inhibitive effects of carbon dioxide and high oxygen concentrations were incorporated by an uncompetitive and a non‐competitive inhibition term respectively. Temperature effects were described using Arrhenius' law. The model gave a good description ( R 2 adj = 0.82) of the oxygen consumption and carbon dioxide production rates over the temperature, oxygen and carbon dioxide range tested. Copyright © 2006 Society of Chemical Industry