Measuring deformation threshold of produce

A method for measuring firmness of a soft fruit, the method comprising:

• a. providing a testing device comprising:
• a probe configured to be advanced to engage a soft fruit positioned in relation to said testing device, wherein said soft fruit is characterized by having a soft texture that is easily mashed to pulp or follow viscous behavior when squashed, and
• at least one sensor configured to measure a resisting force by said soft fruit as a function of an advancement distance;
• b. operating said testing device to advance said probe to engage a surface of said soft fruit while measuring said resisting force;
• c. detecting a first exponentially-increasing resistance response phase of the resisting force occurring between 0.2-0.3 mm of the advancement distance,
• d. detecting a second linearly-increasing resistance response phase occurring between 0.3-3 mm of the advancement distance,
• e. determining a transition point between the exponentially-increasing resistance response phase and the linearly-increasing resistance response phase by monitoring for a decrease in resistance force change between increments of the advancement distance,
• f. discontinuing said advancing, and retrieve the probe when said transition point is detected;
• and
• g. determining for the transition point, a transition resisting force and a transition distance at said transition point, wherein said transition point indicates a beginning of irreversible damage to the soft fruit.