The aim of this study was to compare peeled and unpeeled dehydrated apple slices of the red-fleshed 'Baya Marisa' and the white-fleshed 'Golden Delicious', to analyze the difference in the content of sugars, organic acids, and phenolic compounds during the heat process of dehydration, and to compare it with our previous study on fresh apples of the same cultivar. The purpose of these study was to see how many primary and secondary metabolites are lost in the dehydration process to better understand what is ingested by consumers in terms of nutritional value. A total of 30 phenolic compounds were identified and quantified, some of them for the first time. The total analyzed phenolic content (TAPC) of the unpeeled dehydrated apple slices was 1.7 times higher in 'Golden Delicious' than in 'Baya Marisa'. The unpeeled dehydrated apple slices of 'Golden Delicious' had higher total hydroxycinnamic acid (2.7×) and dihydrochalcone (1.2×) content. The peeled dehydrated apple slices of 'Baya Marisa' had higher total dihydrochalcone (2.2×) and total flavanol (2.2×) content compared to 'Golden Delicious'. The content of citric and malic acids was higher in the unpeeled and peeled dehydrated apple slices of 'Baya Marisa', compared to 'Golden Delicious'. The content of ascorbic acid was higher in the unpeeled (1.6×) and peeled (1.8×) dried apple slices of 'Baya Marisa'. The content of fructose and glucose was 1.4 times higher in the unpeeled dried apple slices of 'Golden Delicious'.
Keywords: HPLC-MS identification; Malus domestica Borkh.; dehydrated apple slices; organic acids; phenolic compounds; processing; sugars.