Metabolome classification via GC/MS and UHPLC/MS of olive fruit varieties grown in Egypt reveal pickling process impact on their composition

The role of variety and effects of pickling on Egyptian olive fruit metabolome was determined using mass spectrometry-based metabolomics targeting nutrients and bioactive metabolities. The analyzed fresh olive fruit varieties included Manzanilo, Picual, Koroneiki, and Coratina, while the pickled samples included the Manzanilo and Picual varieties. Profiling of primary and secondary metabolites resulted in the detection of 201 metabolites. Variation between varieties was mostly observed among sugars, sugar alcohols, secoiridoids, and flavonoids. An abundance of carbohydrates and O-glycosides in Picual and Manzanilo versus enrichment of secoiridoids in Picual and Coratina olives viz. dehyro-oleuropein could account for the difference in palatability and health benefits among varieties. Herein, 13 new compounds are reported in the tested varieties, of which 10 appeared exclusively in pickled samples. Generally, pickled samples were characterized by the relative abundance of secoiridoids regarded as important markers for the pickling process. Metabolites profiling provided greater insight into the pickling process as a preservation method and accounted for the improved organoleptic characters in pickled fruits.