Effects of gas atmosphere and temperature on the respiration rates of whole and sliced mushrooms (Agaricus bisporus)--implications for film permeability in modified atmosphere packages.

An open flowthrough respirometer was used to determine the respiration rates of whole and sliced mushrooms as a function of O2, CO2, and storage temperature. Respiration rates were measured under the following O2 concentrations: 20, 15, 10, 5, and 2% at 5 temperatures (4, 8, 10, 13, and 16 degrees C). The effects of 5 CO2 concentrations (0, 2, 5, 10, 15%) at two O2 levels (2 and 20%) were also examined at these temperatures. Mushroom respiration increased with temperature following an Arrhenius-type relationship; activation energies and corresponding Q10 values were calculated. Lowering the oxygen concentration significantly decreased the respiration rate. The effects of reducing O2 levels were greater at higher storage temperatures. Both activation energies and Q10 values were lower under reduced O2 atmospheres compared with those in air. A Michaelis-Menten enzyme kinetics model was evaluated for describing the influence of gas concentrations on respiration rate. The effects of O2 fitted the O2 enzyme kinetics model well. CO2 exhibited small inhibitory effects on respiration of whole and sliced mushrooms, especially at low O2 concentrations and low temperatures. The enzyme model was used to predict respiration under an optimal modified atmosphere for mushrooms, and the required film O2 and CO2 permeabilities were defined for key pack design parameters.