Relationship between α– and β-galactosidase activities and firmness loss during the development of Vitis vinifera L. grape berries

Firmness is an essential organoleptic quality parameter of Vitis vinifera L. table grapes and is also a desirable feature for their optimal storage.
In grape, texture loss is associated with a series of physicochemical changes that are affected by genetic, climatic and agricultural factors.
A reduction in firmness may be caused by a drop in turgor pressure or by physiological changes in the tissue that weaken the structure.
These changes are related to the degradation of the polysaccharides of the middle lamella and primary wall, and result from the activity of different cell wall-modifying enzymes.
The aim of this study was to determine the relationship between α- and β-galactosidase enzyme activities and firmness loss during ripening in table grape.
For this, ten cultivars of table grape (Vitis vinifera L.), ‘Muscat Alexandrie’, ‘Muscat Hamburg’ and ‘Moscatuel’ (classified as soft cultivars), ‘Autumn Seedless’, ‘Ohanes Cid’, ‘Dominga’ and ‘Ruby Seedless’ (cultivars of intermediate-firmness) cultivars, and ‘Dona Maria’, ‘Italia’ and ‘Napoleon’ (crispy cultivars) were selected and harvested at six different stages of development, from preveraison to ripening.
The maturity index, texture and enzymatic activities were determined for each maturity stage.
Three main texture profile models were defined.
The first step, characterized the stages 1 and 2 with high firmness values, the second (3 and 4 stages) resulted in a drastic texture loss and the third profile model, represented by the last stages, showed a slight reduction in berry firmness with respect to the previous stage.
The α- and β-galactosidase enzyme activities were determined at all stages of berry development.
In general and for all cultivars, enzyme activities increased while firmness decreased during ripening.

VIII International Postharvest Symposium: Enhancing Supply Chain and Consumer Benefits – Ethical and Technological Issues

S. Fuentes, J. Fenoll, J. Cava, I. Garrido, M.V. Molina, P. Flores, P. Hellín

cell wall hydrolases, berry softening, firmness, ripening, mechanical properties

https://doi.org/10.17660/ActaHortic.2018.1194.60