Changes in cell wall galactosyl and soluble galactose content in tomato fruit stored in low oxygen atmospheres

Abstract

Mature green tomato (Lycopersicon esculentum Mill.) fruit were stored in atmospheres of low oxygen (3.05 kPa; 3%) or air (control) at 20 degrees C. Their subsequent ripening behavior was compared in an effort to evaluate the temporal relationship among ethylene production, respiration, cell wall galactosyl residue loss and the increase in free galactose that occurs during ripening. An increase in ethylene evolution and respiration, red color development, and loss in fruit firmness were delayed in fruit held in low oxygen compared to control fruit held in air which showed normal ripening-related changes. Both the ripening-related decrease in cell wall galactosyl residues and the increase in soluble galactose were suppressed for 9 days in fruit held in low oxygen. However, after 9 days of storage, these processes did commence and changed significantly by 13 days of storage. These results suggest that either only relatively low baseline levels of ethylene were necessary for it to exert its effect on these cell wall-related fruit ripening processes to occur or that the cell wall-related changes observed were ethylene independent. It is clear that the levels of ethylene generally produced during the respiratory climacteric were not necessary to begin the processes associated with cell wall modification, such as the large net loss of galactosyl residues from the cell wall during tomato fruit ripening. (C) 1999 Elsevier Science B.V. All rights reserved.