The base colour of fruit as an indicator of optimum harvest date for two apple cultivars (Malus domestica Borkh.)

The CIE L^* a^* b^* colour system is used to evaluate food colours. Its advantage is that the base skin colour in apples can be measured on the same fruit before and on the optimum harvest date. The aim of the research conducted between 2002 and 2006 was to evaluate a quick and non-destructive method of determining the optimum harvest date of apples intended for long storage based on the changes observed in the base skin colour. Another important research aspect was to compare this method with other methods or indicators used to determine the harvest date. The colour measurement was conducted on two apple cultivars, Šampion and Royal Gala, with the aim of, amongst other factors, establishing a standard for each that could be used in practice in fruit production. From amongst the evaluated colour indicators L^*, a^*, b^*, Hue_ab angle and chroma, changes in the base colour were best illustrated by the a^* coordinate value and Hue_ab angle value. Based on the evaluation of the quality of fruits after storage, it can be stated that the fruits had the best quality when the a^* coordinate during harvest ranged between -7 and -8 for ‘Šampion' and between -3 and -5 for ‘Royal Gala’. The Hue_ab angle assumed a value between 100 and 101 for ‘Šampion' and between 96 and 99 for ‘Royal Gala’ during the optimum harvest date. Therefore, the a^* coordinate and the Hue_ab angle can be used to indicate harvest maturity.