|
Effect of gamma-radiation in cell wall-degrading enzymes of papaya (Carica papaya L.) during fruit ripening
Soprani, J.1,2; Lopes, B.F.2; Silva, G.G.2; Farias, L.B.2; Medeiros, E.F.2; Santos, R.G.1; Figueiredo, S.G.2
1Laboratório de Radiobiologia, CDTN/CNEN, Belo Horizonte, MG; 2Laboratório de Química de Proteínas, UFES, Vitória, ES.
Papaya (Carica papaya L.) is a fragile, perishable fruit, highly accepted worldwide. Its softening during fruit ripening is correlated with the activities of pectinolytic enzymes (polygalacturonase (PG), b-galactosidase and pectinamethylesterase) which are responsible for the solubilization of pectins, responsible for preservation of fruit firmness along the ripening process. Among the techniques for conserving fresh products to ensure palatability and pulp firmness after handling and transportation, gamma-radiation is a technique of choice. The objective of this work was to evaluate the effect of gamma radiation in cell wall-degrading enzymes activities, involved in solubilization of pectins and alteration of the texture in papaya's fruits at post-harvest. Papayas were harvested in perfect quality conditions and selected by skin coloration into maturation 2 degree. The fruits were irradiated with 0.8 kGy (Cobalt 60 source-MSD Nordion irradiator). Three fruits irradiated and 3 fruits control were evaluated daily during their shelf life by analyzing pulp firmness (determined through a Penetrometer - flat pointed, diameter 0,8cm) expressed in Kilogram force (Kgf) and activity of the pectinolytics enzymes, PG and b-galactosidase via spectrofotometric methods.The results showed a direct correlation between the pectinolytic enzymes activities and loss of texture. In relation to the control, irradiated papaya presented firmer than the controls in the daily analysis (26% on 1st day after irradiation treatment; 54% - 2nd; 70% - 3rd; 65% - 4th; 43% - 5th; 50% - 6th; 84% - 7th,) presenting best visual aspect. Furthermore, they lasted 4 days longer than the controls. Dose of 0.8 kGy decreased 20 – 40% the b-galactosidase activity in the daily analysis and delayed the maximum activity of PG by one day on irradiated fruits. The activity reduction was followed by a lesser reduction of the loss pulp firmness for the irradiated fruits demonstrating that this delay in ripening on irradiated fruits be due to the effect of irradiation in the activity of cell wall-degrading enzymes. Supported by PIBIC/ CNPq; CDTN.
|