Nondestructive firmness sensing using a laser air-puff detector

Abstract

Abstract Recent studies indicate that peaches harvested at the right maturity stage are preferred by consumers. Reliable means of assessing peach maturity will increase efficiency and reduce costs. Current methods for determining harvest maturity of peaches are either subjective or destructive and are inherently inconsistent and wasteful. Nondestructive and objective methods for maturity sensing are needed. A laser air-puff firmness detector (consisting of a sample holder, a surge air tank, a displacement laser sensor, and a solenoid valve) was used to nondestructively measure the firmness of an engineered rubber ball inflated to an internal pressure of 13.8–34.5 kPa, and then three cultivars (Dixie Red, Harvester, and Sun Prince) of peaches at different maturities. The readings were related to peach mass and the penetrometer firmness from the Instron universal testing machine. The rubber ball deformation increased linearly as the tank air pressure increased ( R 2 =0.94 and 0.97). The firmness of the rubber ball indicated by compression tests was highly correlated with the firmness indicated by the laser air-puff detector ( R 2 =0.985). Peach mass and nondestructive deformation both increased and destructive penetrometer firmness decreased with time towards the optimum picking date. These results show that the laser air-puff firmness detector was able to sense the firmness of peaches. Multiple regression analysis showed a significant correlation among laser air-puff, penetrometer firmness, and mass data of peaches ( R 2 =0.774).