Firmness classification of tomato by mechanical nondestructive impact technique

Abstract

In this study, firmness classification of tomato was aimed by using mechanical nondestructive impact technique. Bandita F1 tomato variety was used during the tests. In the nondestructive impact measurements done by lateral impactor with low impact energy, impact acceleration and contact time were sensed by an accelerometer attached on impact head, and main impact parameters (maximum impact acceleration, time required to reach maximum acceleration and contact time) were extracted from the curve. Other impact parameters were derived from the main impact parameters and theory of elasticity. These nondestructive impact parameters were compared with destructive reference parameters. Forcedeformation ratio at rupture point was used in the measurements of destructive reference parameter and this was expressed to be tomato firmness. Cluster analysis was used for firmness groups of tomatoes. Furthermore, linear discriminating analysis was used to find an optimum linear combination of the impact parameters that minimizes the probability of misclassifying tomatoes into their respective groups for firmness classification procedure of tomatoes. The accuracy of classification was improved with linear discriminating analysis, and the number of parameters being processed was reduced with stepwise regression analysis. Statistical analysis showed that the correlations between destructive reference and nondestructive impact parameters were significant. According to the results of linear discriminating analysis, accuracy of the best classification for main impact parameter approach and all ten impact parameters approach was found to be 77.27% and 81.82%, respectively. Furthermore, linear discriminating analysis results for three most important impact parameters obtained with stepwise regression analysis showed that accuracy of the best classification of tomatoes was improved to 82.96%. As a result, mechanical nondestructive test device tested in static conditions gave high accuracy of classification for tomato. This performance shows that mechanical nondestructive impact technique could be used for real-time firmness classification of tomatoes in the electronic sorting line. © 2020 Elsevier B.V., All rights reserved.