Changes in cell-wall-degrading enzyme activities in stored olives in relation to respiration and ethylene production Influence of exogenous ethylene

 The activity of various enzymes (α-D-galactosidase; β-D-galactosidase; α-L-arabinofuranosidase; α-D-mannosidase, β-D-N-acetylglucosaminidase, cellulase and polygalacturonase) associated with the cell wall during olive storage was assayed in order to establish the behaviour of the enzymes as a function of the ripening stage and in relation to the production of ethylene. The effect of exogenous ethylene (100 mg/l for 24 h) was also evaluated. In addition, gaseous emissions of CO₂ and ethylene during olive storage were monitored. The results obtained indicate that the high initial CO₂ level in the green olive coincides almost exactly in time with the climacteric maxima when the fruit is on the tree. After the rapid decrease in the respiration rate of green olives during storage, the CO₂ production rate increases as the stage of maturity advances. The results also indicate that ethylene is not capable of stimulating the activity or synthesis of enzymes in green olives, but can produce such a stimulation in black olives. Furthermore, during the first day of storage there were very marked decreases in enzyme activities. Small variations in the conditions of aerobiosis in post-harvest ripening were shown to have notable effects on the normal metabolism of the fruits. Received: 29 January 1996 / Revised version: 1 July 1996