ISHS Acta Horticulturae 682: V International Postharvest Symposium
RELATIONSHIP BETWEEN PHYSICAL AND BIOCHEMICAL PARAMETERS IN APPLE SOFTENING |
| Authors: | E. Róth, E. Kovács, M.L.A.T.M. Hertog, E. Vanstreels, B. Nicolaď |
| Keywords: | acoustic stiffness, cell wall, polygalacturonase, bruise susceptibility |
| Abstract:
Postharvest softening of apple is one of the most important problems resulting in quality losses for growers and distributors all over the world. Factors affecting apple softening must be well known to provide a good quality apple to the market all year round. Therefore, our research focuses on the physical and biochemical parameters causing and related to apple softening. Rapid postharvest softening of apple is the result of an undesired, fast ripening process. The two main reasons for apple softening are water loss due to transpiration and cell wall breakdown due to enzymatic activities. The former has a considerable influence on the turgidity of the cells (thus on the stiffness of apple), while the latter affects mainly the firmness of the apple due to reducing the mechanical strength of cell walls. The apple cultivar ‘Delbard Estival’ was studied during 2 months storage at 18°C, 80-90% relative humidity (shelf life conditions). The acoustic stiffness coefficient, water potential, Brix value, penetrometer firmness, bruise susceptibility and activity of polygalacturonase were investigated. Both the acoustic stiffness coefficient and penetrometer firmness decreased considerably during storage following the characteristic three phase softening curve. Water potential and bruise susceptibility also decreased during storage due to the decrease in turgidity of the apple tissue. The activity of polygalacturonase showed an exponential increase in the first 30 days. The acoustic stiffness coefficient during storage was largely determined by the initial stiffness. The acoustic stiffness coefficient related to penetrometer firmness and water potential. There were also correlations found between water potential and soluble solids content. Bruise susceptibility was affected by both stiffness and the weight of the fruit. | |
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