Influence of harvest date on physicochemical properties and flesh image parameters of red-fleshed apples

The harvest date affects the ripeness and properties of apples. The objective of this study was to compare the properties of red-fleshed apples ‘Alex Red’, ‘Trinity’, and ‘Roxana’ harvested on August 31 and September 06, 2021. Color parameters (L*, a*, b*) and image textures of the flesh, as well as the content of chemical compounds were determined. The values of parameter L* of the flesh statistically significantly decreased for apples sampled on the second date, from 54.4 to 50.5 for ‘Alex Red’, from 51.6 to 47.0 for ‘Trinity’, and from 71.9 to 69.5 for ‘Roxana’. The significant increase in parameter a* for ‘Alex Red’ (29.1 to 32.8) and ‘Trinity’ (33.0 to 36.3) and parameter b* for ‘Trinity’ (11.1 to 12.7) and ‘Roxana’ (11.8 to 14.0) were determined. The greatest significant changes in image texture HMean were found for color channel R, from 228 to 236 for ‘Alex Red’, from 232 to 236 for ‘Trinity’, and from 218 to 228 for ‘Roxana’. A significant increase in sugar content from 85.6 to 90.9 g kg^-1 for ‘Alex Red’ and from 112 to 128 g kg^-1 for ‘Trinity’ was observed. The total phenolic content significantly decreased with harvest delay, from 536 to 502 mg kg^-1 for ‘Alex Red’ and increased from 516 to 573 mg kg^-1 for ‘Trinity’, and from 1121 to 1293 mg kg^-1 for ‘Roxana’. The obtained results indicate that a weekly interval of harvesting red-fleshed apples can significantly affect the composition of chemical compounds, as well as flesh color intensity.