Temperature effect on skin resistance to CO2 mass-transfer in golden delicious apples stored in controlled atmosphere

Mass transfer of O-2 and CO2 through the skin of fruit: stored in refrigerated and controlled atmospheres could potentially represent the rate determining step of their aerobic respiration process and then also affect their shelf life. The mass transfer rate of the two respiratory gases was evaluated in Golden Delicious apples as a function of temperature (21 degrees, 16 degrees, 11 degrees, 6 degrees, 1 degrees C) by looking at the values assumed by the constants (k(i), H) connected to the kinetic equation introduced to describe this diffusion process. Neither for O-2 nor for CO2 diffusion, did any significant temperature variation result for the equilibrium constant H, which gives a measure of the total amount of gas that has permeated into the fruit when equilibrium with the surrounding atmosphere is reached, As the large fraction of gas which has permeated into the fruit fills the intercellular space (about 21-23% of total apple volume), the constant H did not vary significantly, at least in the range of temperatures tested. On the contrary, the temperature effect on the global mass-transfer constant k(i) seems to depend on the gaseous species, While for O-2 no change in temperature could be perceived, a slight but significant decrease of k(i) was detected for CO2 when temperature decreased, This temperature development follows Arrhenius' law and the related activation energy was equal to 3.55 kcal/mol.