Physiology and Prediction of Fruit Tolerance to Low-oxygen Atmospheres

Abstract

Fruits of `Granny Smith' and `Yellow Newtown' apples (Malus domestica Borkh), `20th Century' pear (Pyrus serotina L.), and `Angeleno' plum (Prunus domestica L.) were kept in air and in 0.25% or 0.02% O 2 at 0, 5, or 10C for 3, 7, 14, 25, or 35 days to study the effects of low-O 2 atmospheres on their postharvest physiology and quality attributes. Soluble solids content (SSC), pH, and external appearance were not significantly influenced, but resistance to CO 2 diffusion was increased by the low-O 2 treatments. Exposures to the low-O 2 atmospheres inhibited ripening, including reduction in ethylene production rate, retardation of skin color changes and flesh softening, and maintenance of titratable acidity. The most important detrimental effect of the low-O 2 treatments was development of an alcoholic off-flavor that had a logarithmic relation with ethanol content of the fruits. The ethanol content causing slight off-flavor (E o ) increased with SSC of the commodity at the ripe stage, and it could be estimated using the following formula: (Log E o )/SSC = 0.228. Using SSC of ripe fruits and average ethanol accumulation rate per day (V E ) from each low-O 2 treatment, the tolerance limit (T l ) of fruits to low-O 2 atmospheres could be predicted as follows: T l = E o /V E = (10 0.228SSC )/V E .