Primary and secondary metabolites as a tool for differentiation of apple juice according to cultivar and geographical origin

The presented study addresses the use of primary and secondary metabolites to differentiate apple juice according to the cultivar and geographical origin. Three apple cultivars were included: Idared and Golden Delicious from integrated/conventional agriculture practice and Topaz, which was produced organically from five different geographical regions in Slovenia: Alpine, Dinaric, Pannonian, Mediterranean and Submediterranean. Especially the minor phenolic compounds flavanols and flavonols, were confirmed as unambiguous and reliable markers of authentic apple juice for geographical origin differentiation including: flavanols (catechin, epicatechin, procyanidin B1 and procyanidin B2+B4); flavonols (quercetin-3-rhamnoside and quercetin-3-glucoside + quercetin-3-galactoside) and the levels of trans-piceid. The overall prediction ability was 60.9%, where only samples of apple juice from the Alpine region were sufficiently separated from the Mediterranean ones. Complete separation between three apple cultivars was achieved, when all the detected metabolites (with the exception of glucose and malic acid) were included in the Liner Discriminant Analysis (LDA).