TEMPERATURE EFFECT ON SKIN RESISTANCE TO O-2 AND CO-2 MASS-TRANSFER IN GOLDEN DELICIOUS APPLES STORED IN CONTROLLED ATMOSPHERES

Mass transfer of O-2 and CO2 through the skin of fruit: stored in refr igerated and controlled atmospheres could potentially represent the ra te determining step of their aerobic respiration process and then also affect their shelf life. The mass transfer rate of the two respirator y gases was evaluated in Golden Delicious apples as a function of temp erature (21 degrees, 16 degrees, 11 degrees, 6 degrees, 1 degrees C) b y looking at the values assumed by the constants (k(i), H) connected t o 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 measur e of the total amount of gas that has permeated into the fruit when eq uilibrium with the surrounding atmosphere is reached, As the large fra ction of gas which has permeated into the fruit fills the intercellula r space (about 21-23% of total apple volume), the constant H did not v ary significantly, at least in the range of temperatures tested. On th e contrary, the temperature effect on the global mass-transfer constan t 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 temperat ure development follows Arrhenius' law and the related activation ener gy was equal to 3.55 kcal/mol.