Firmness Classification of Tomato Fruits by Using Colour Parameters

Abstract

Aim of study: In this study, firmness classification potential of tomato fruits was investigated by using colour parameters measured with a colour measuring device. Material and methods: 202 ‘Bandita F1’ greenhouse tomatoes were used as trial material. In damage free colour measurements carried out by Minolta CR-400 colour measurement device, L*, a* and b* colour parameters were considered as main parameters. Other colour parameters (a*xb*, a*2, b*2 and a*/b*) were derived from main colour parameters. These colour parameters were associated with tomato firmness. In tomato firmness measurements, the force value at the skin rupture point was used and this value was expressed as tomato firmness. Tomato samples were grouped according to firmness by using clustering analysis method. In addition, linear discrimination analysis method was used in the classification of tomatoes according to firmness. Classification accuracy was improved by linear discrimination analysis and the number of parameters used was decreased with stepwise regression analysis method. The association between tomato firmness and colour parameters (L*, a*, b*, a*xb*, a*2, b*2 and a*/b*) was determined with Pearson Correlation test. Main results: Statistical analysis results showed that the association between tomato firmness and colour parameters was significant (P<0.01). According to linear discrimination analysis results, linear classification accuracy was calculated as 85.64% for main colour parameters approach and as 90.59% for seven colour parameters approach. The results of linear discrimination analysis performed by using the most important three colour parameters determined with stepwise regression analysis method showed that correct classification accuracy of tomatoes was 89.10%. Research highlights: The results showed that firmness classification of tomatoes could be done by using colour parameters and linear discrimination analysis method.