|Perkins Veazie, Penelope|
Submitted to: International Food Technology Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 12/7/1999
Publication Date: 6/13/2000
Technical Abstract: Various methods are currently used to determine fruit firmness of blackberries. Quantitative methods, such as penetrometer measurements of drupelet skin puncture force, or compression measurements of whole berries, are destructive, extremely lengthy, and correlate poorly with perceived firmness. Squeezing the fruit between fingers and subjectively classifying firmness on a numerical scale gives a better gauge of fruit firmness but requires trained and experienced graders, is laborious, and prone to misclassification due to grader fatigue. A rapid, quantitative and non-destructive method would be ideal for variety selection and post- harvest research. Our approach to this problem was to determine the force- deformation loading characteristics of blackberry fruit and establish parameters from these tests that would be useful for defining firmness. Two cultivars, Arapaho (firm) and Choctaw (soft), were subjected to force- deformation measurements using freshly harvested fruit at early and late stages of harvest. Different parameters were extracted from the force- deformation curves and used to determine which of these parameters provided the best discrimination between very firm and soft fruit. The parameter considered to have the best firmness discrimination was the linear slope of the force-deformation curve between 1 mm and 2 mm of deflection. Parameters will be incorporated into future firmness measurements to validate their use as an indication of firmness and quality.