Soft tropical fruit assessment based on a non-contact on destructive experimental modal analysis with laser technique

Conventional assessment methods of the quality of fruit may not be evaluated to fruit whose acidity or sugar content does not change during ripening after harvest. Therefore, many researchers have studied to examine the firmness of fruit as their ripeness using dynamic characteristics such as natural frequencies or vibration mode shapes because the firmness is strongly correlated to the ripeness. When the target fruit to be assessed is kind of soft tropical fruit such as a mango, etc., it might be difficult for the traditional methods to measure their dynamic characteristics (natural frequencies or vibration mode shapes) without any damages because those fruit have viscoelastic characteristic strongly. In this study, we demonstrated a non-contact and nondestructive vibration test of a mango, a papaya and a dragonfruit based on laser-induced plasma (LIP) shock wave impulse excitation. We conclude that our method can monitor the change of firmness of the soft tropical fruit.