Compositional characterisation of some apple varieties

Abstract

Ten apple varieties, harvested at commercial maturity, were analysed, paying special attention to the level of phenolic compounds and polyphenol oxidase (PPO) activity. The results pointed to great quantitative differences in the composition of the apple varieties, and particularly in their phenolic contents. Their total polyphenol content ranged from 2.3 to 3.6 g/kg. Chlorogenic acid was the main phenolic compound found in the varieties studied, and its concentrations varied from 30 to 430 mg/kg, and were 4–20 times higher than those of catechins. Only in Szampion and Elstar were the concentrations of catechins higher. Amongst the flavanol monomers, the main compound was (–)epicatechin, whose concentration varied from 18 to 89 mg/kg. The (+)catechin concentration ranged from 4 to 21 mg/kg. The dominant proanthocyanidins were oligomers up to trimers. In Warta apples, the concentrations of these oligomers were about 3 times higher than those of monomers. The level of PPO activity ranged from 270 units (U)/g in Szampion to 3120 U/g in Warta. No correlation was found between the concentrations of certain phenolic compounds, nor between PPO activity and phenolic or ascorbic acid concentrations. The results gave important information regarding the best use of the apple varieties investigated, i.e. for direct consumption due to their high nutritional value, or for processing.