NONDESTRUCTIVE METHOD FOR MEASURING FIRMNESS OF BLUEBERRY FRUIT

摘要

Flesh firmness is commonly used to monitor changes in fruit quality during handling and storage. Destructive techniques may not be effective in detecting small variations in firmness, since they tend to have higher variability due to single measurements of different fruit. The objective of this study was to determine if blueberry firmness could be nondestruc-tiveiy measured by determining resistance to a small deformation made in the elastic region. Individual blueberries were compressed up to 1.25 mm between two parallel plates to obtain force-deformation curves. Fruit were oriented in the same position for repeated measurements up to 14 days. The shapes of the resultant force-deformation curves varied with fruit orientation. Fruit compressed alongthe equator exhibited smoother and more consistent force-deformation curves than fruit compressed in the axial direction.Deformation energy values did not always decrease with time of fruit storage or weight loss. Once the elastic region was reached, four successive compression cycles on the same berry, made 15 minutes apart, resulted in similar force-deformation curves and energy levels. This suggests that these curves could be used as indicators of fruit firmness over time. This nondestructive technique shows promise for evaluating postharvest quality changes in blueberries and merits more extensive testing.