A Firmness Sorting Criterion for Blueberries
ABSTRACT A nonlinear differential equation was used to model the contact force of the rebounding blueberry. Model parameters were determined by a least squares curve fitting algorithm resulting in correlations of 0.98 for model mass with berry mass and 0.62 for model firm-ness with berry firmness. The peak force parameter (pro-portional to max force/square of time to max force) can be determined quickly and correlates well with model firmness (R = 0.87).