Prediction of Fruit Maturity with Starch Pattern Index in Korean Apple Cultivars

Abstract

This study was conducted to evaluate the starch loss pattern and to estimate the maturity indices and harvest time of the five Korean apple cultivars (‘RubyS’, ‘Arisoo’, ‘Hwangok’, ‘Picnic’, and ‘Colorpple’) in association with the changes of fruit quality attributes using a Cornell starch pattern index (SPI) analysis method (1-8 scores) and SPI chart development for domestic use. In 5 apple cultivars, the increase in SPI was directly related with the increase in fruit weight and soluble solids content and the decrease in flesh firmness and titratable acidity. For fruit peel coloration, the decrease in L* (indicator for brightness) and b* (indicator for yellowness) was strongly associated with the increase in SPI. In addition, the increase in a* (indicator for redness) was associated with the increase in SPI in all apple cultivars, except ‘Hwangok’, a yellow apple cultivar. A slight increase in internal ethylene concentration was also observed in all cultivars while the SPI was increased. Interestingly, the changes of SPI were different depending on each apple cultivar. Averagely, ‘RubyS’, ‘Arisoo’, ‘Hwangok’, and ‘Picnic’ apples took 3, 4, 5, and 7 days, and 7, 5, 7, and 7 days to change the SPI from 6 to 7 and from 7 to 8 scores, respectively. However, ‘Colorpple’ apple took about 10 days each to change the SPI from 6 to 7 and from 7 to 8 scores. Therefore, this study suggested that the development of SPI chart could be used as basic data to estimate the fruit maturity and harvest time of domestic apple cultivars.