The total polyphenolic contents, as well as the major groups and individual compounds, varied significantly
among the eight studied apple cultivars grown in Ontario. In general, the peels have a much higher concentration of polyphenols than does the flesh, and different cultivars had significantly different levels of total polyphenolic concentrations. Red Delicious and Northern Spy had the highest concentrations among the eight cultivars, and Empire had the lowest. Five
major polyphenolic groups with a total of 16 identified individual compounds were found in the apples studied, among
which the dihydroxycinnamic acid esters, phloretin glycosides, and flavan-3-ols were found in both flesh and peel, whereas
quercetin glycosides were almost exclusively found in the peel.