A TENTATIVE MODEL TO DESCRIBE THE RESPIRATION OF STORED APPLES

Using mathematical equations that describe the O2 mass-transfer and the enzymatic oxidation of the organic substrates of apples (Malus domestica Borkh.), we developed a kinetic model to correlate fruit respiration rate with environmental oxygen partial pressure (PO2). The kinetic determinations were carried out at room temperature using apples stored at 3 to 4C for 11 to 19 weeks. Results show that: 1) the calculated value of the Michaelis-Menten constant related to the enzymatic oxidation of the respiratory substrate (K(m) = 2.1 +/- 0.5.10(-5) mol.kg-1) is close to that reported in the literature for cytochrome-c oxidase; 2) the located range of PO2 levels where O2 becomes the limiting factor in the respiration process (near 2.6 kPa at T = 20.5 +/- 1C) is close to those usually used on a commercial scale for controlled atmosphere storage.