Modelling respiration rate of shredded Galega kale for development of modified atmosphere packaging

The design of modified atmosphere packaging (MAP) for fresh-cut produce requires an adequate model for prediction of respiration rate as a function of both temperature and gas composition. In this work, the O₂ consumption and CO₂ production rates of shredded Galega kale were studied. The storage temperatures used were 1, 5, 10, 15 and 20 °C. The atmospheres tested were all combinations of 1, 5 and 10% v/v O₂ plus 0, 10 and 20% v/v CO₂ with the balance being N₂, as well as ambient air. Temperature was the variable with the greatest influence on respiration rate and the effect of gas composition increased with temperature. The dependence of respiration rate on gas composition was well described by a Michaelis-Menten type equation with uncompetitive CO₂ inhibition. The respiratory quotient (RQ) was found to be constant for the range of temperatures and gas compositions tested and was equal to 0.93 ± 0.01. The constants of the Michaelis-Menten equation increased exponentially with temperature. The change over time of respiration rate of leaves exposed to air at 20 °C was also analysed. It was observed that respiration rate decreased with time and that the ratio between the respiration rate of shredded and intact leaves was approximately constant in the period tested and equal to 2.8.