The effect of irradiation on sweet cherries

The effect of irradiation (1, 2.5 and 5 kGy) and packaging (Resinite VF71) on the shelf life of cherries (Prunus avium cv. Germersdorfi orias) was studied. Cherries were stored for 7-26 (3-5°C, 90% RH). The spoilage, weight loss, texture, sugars and organoleptical properties (color, taste, texture, surface) were determined. The ultrastructure of cells (SEM, TEM, image analysis) and cell wall of the packed and stored (7 d) cherries were investigated. Irradiation (2.5 kGy and 5 kGy) reduced spoilage after 7 wk of storage at 3-5 °C from 60% to 20%. Packaging inhibited spoilage, by 20% (from 50% to 30%), and weight losses nearly completely (from 3-5% to 0.2-0.3%). Combined treatment (2.5 kGy and packaging) resulted in the best results: spoilage was in average 10%. Irradiation (2.5 kGy) induced softening (P > 95%). During storage time softening increased (P > 95%) both in the control and in the irradiated cherries. However, panelists could not establish significant differences between texture of control and irradiated cherries. The ultrastructure of cells in the cherries showed great heterogeneity (cell size, thickness of cell wall, integrity of cell compounds). Cells of the cortex in irradiated cherries were more wrinkled (SEM) than in the control. The middle lamellae of cell wall dissolved moderately in the irradiated (1, 2.5 kGy) cherries (TEM). Glucose and fructose were detected in cherry. The quantity of these sugars did not change with the increasing radiation dose. During storage fructose concentration increased, glucose concentration decreased. On the basis of these results irradiation (2.5 kGy) can be applied for extension of the shelf life of cherry. Three times longer storage time (at 3-5 °C, 90% RH) can be obtained by irradiation, even longer by using irradiation combined with packaging.