Relationships Between Chemical Properties, Color Parameters, and Image Features of New Clones of Apples (Malus domestica L.) from Ecological Cultivation

This study aimed at determining the relationships between the selected quality properties of four new apple clones: ‘Free Redstar’ × ‘Melfree’, ‘Free Redstar’ × ‘Ariwa’, ‘Free Redstar’ × ‘Rajka’, and ‘Free Redstar’ × ‘Rubinola’. Significant differences between the selected clones in terms of quality properties were revealed. For example, the ‘Free Redstar’ × ‘Ariwa’ clone had the highest total sugar content (132.7 g kg−1) and total polyphenol content (TPC) (260.7 mg 100 g−1 GAE), while ‘Free Redstar’ × ‘Rajka’ was characterized by the highest total acid level of 739.0 mg 100 g−1 and the lowest a* value of −0.62, which were significantly different from all other clones. Correlations between image textures and chemical and color characteristics were observed. Among the sugars, sucrose showed the strongest positive correlation with the selected texture parameters of images in color channel Y, obtaining a Pearson correlation coefficient (R) of 0.946, while sorbitol had the strongest negative correlation (R = −0.946) with the selected texture of images in color channel b. In terms of acids, the Pearson correlation coefficient was up to 0.953 for the relationship between the content of citric acid and the selected texture of images in color channel G, and for TPC, the value of Pearson’s correlation coefficient reached 0.921 for the selected texture feature of images in color channel X. Regarding color parameters, the correlations were also strong, reaching 0.945 between parameter a* and the selected texture of the images in color channel a. These findings provide insights into the potential use of image texture analysis in combination with chemical profiling for evaluating apple quality and clone differentiation.