Controlled-atmosphere storage of tomato fruit: low oxygen or elevated carbon dioxide levels alter galactosidase activity and inhibit exogenous ethylene action

The effects of 3% O-2 and 20% CO2, both alone and together with 100 mu g g(-1) C2H4, on ethylene production, chlorophyll degradation, carotenoid biosynthesis and alpha- and beta-galactosidase activity in breaker tomato (Lycopersicon esculentum Mill) fruit were investigated. The low O-2 and high CO2 atmospheres prevented the rise in ethylene production, total carotenoid and lycopene biosynthesis and alpha- and beta-galactosidase activity and slowed down chlorophyll degradation and loss of firmness (P<0.05). These suppressive effects were not reversed, or only in part - in the case of chlorophyll breakdown - by addition of 100 mu g g(-1) C2H4 to said controlled atmospheres. After transfer from the various atmospheres to air, flesh firmness decreased and ethylene production, total carotenoids, lycopene and beta-galactosidase II activity increased but these parameters were, in all cases, still significantly different from those of fruit held in air. Keeping tomatoes in controlled atmospheres, even in the presence of ethylene, had marked residual effects. Results suggest an antagonism between elevated CO2/low O-2 and exogenous ethylene which could determine most of the ripening parameter behaviour under controlled-atmosphere storage, though a direct regulatory mechanism by O-2 and/or CO2 should not be discarded. (C) 1999 Society of Chemical Industry.