An efficient laser sensor system for apple impact bruise volume estimation

Fruit are subjected to several external loads during processes from the orchard to the market, which result in bruising and therefore, quality loss. In this study, we developed a system based on a line laser light source and light detector for a rapid and efficient estimation of the bruise volume of apples (Malus domestica Borkh L. cv. Starking Delicious) dropped from a certain height onto a steel impact plate. We measured two parameters, namely rise time and dwell time, extracted from response signals generated by the proposed system during the impact test. These parameters are related to contact time, showing how long the fruit remains in contact with the impact plate. The experiments were conducted at six different drop heights and two different temperatures. It was found that there was a strong relation with coefficients of determination of more than 0.93 between bruise volume and dwell/rise time, in which the bruise volume decreased with the increasing rise time/dwell time as a power function. Furthermore, the results showed that warm apples developed greater bruise volume than cold fruit, and the estimated regression lines and curves for cold fruit had higher coefficients of determination than those of warmer fruit.