Relationship of Color Indices with Some Chemical Characteristic in Red and White Apple Cultivars

Abstract   Background and Objectives Apple is one of the most important common fruit trees in temperate regions of the world with a lot of phenotypes and genotypes. Fruit surface color is one of the important factors in evaluating the qualities and appearance of fruits. This is the first component of acceptance by the customer, which indicates anomalies in agricultural products.   Materials and Methods For this purpose, a study was conducted in 2016 in a completely randomized design with 12 varieties of native and imported apples in three replications. In this research, qualitative characteristics including anthocyanins for skin and flesh fruit, total sugar, flavor index, pH and EC and color indexes including brightness index (L), redness index (a), yellowness index (b), Hue (H), and Chroma (C) were measured for each apple cultivar.   Results The results showed the highest indexes of a and C of skin. Moreover, the index of a related to the flesh of fruit in Mazand 2 had the highest levels of Hue skin, brightness and Hue flesh in Gala cultivar. The highest amount of brightness and yellowneass of fruit skin and flesh was observed in Golden delicious cultivar. While the highest amount of anthocyanin in skin was found in Red delicious cultivar. the highest amount of anthocyanin in flesh was found in Mazand 2. Furthermore, the highest level of flavor index was found in Shahrod 10 and the maximum amount of total sugar was detected in Red delicious cultivar. The utmost EC juice and the highest juice pH were observed in Gol Ghermez and Golab Kohanz cultivars, respectively. The highest positive correlation was found between anthocyanin of skin and anthocyanin of fruit pulp in the red flesh apple (0.99).  Based on the results of this research, the red index and the fruit flavor index correlated with skin Hue, brightness of skin correlated with yellow color of skin, and fruit EC correlated with sugar content of the fruit.   Discussion Finally, the highest correlation was found between anthocyanin in skin and the red flesh apple. In other apple cultivars, a significant correlation was found between index (a) and the yellowness of the apples (0.92). Further positive correlation was set between index C and anthocyanin content and flavor index. A positive correlation was observed between H and L indexes and the yellow color of the apple. Index b indicated a significant negative correlation with anthocyanin of skin and flesh of apple. The highest red content in red flesh apples indicated positive correlation with a and c indices, which has already been confirmed by the results of other researchers.