Clarification of morphological traits of unexplored 'Mortarella' and 'Camponica' hazelnut cvs. From the Campania region of Italy, to enhance their shell polyphenol diversity

European hazelnuts are widely cultivated as raw materials in the food industry. Processing produces several non-value-added byproducts, e.g. pericarp and episperm. Herein, the 'Camponica' and 'Mortarella' cultivars were characterised using International Union for the Protection of New Varieties of Plants guidelines. The in-depth analysis of the chemical profiles of different particle size sieved fractions from hazelnut outer pericarps was performed following ultrasound-assisted extraction and ultra-high-performance liquid chromatography-high-resolution mass spectrometry (UHPLC-HRMS). Total phenolic, flavonoid, and tannin contents were evaluated, as well as their radical scavenging capacity using 2,2-diphenyl-1-picrylhydrazyl and 2,2-azino-bis-3-ethylbenzothiazoline-6-sulphonic acid assays. The outer shell extracts mainly contained ellagic acid derivatives, giffonins, and flavonol glycosides. The inner pericarp and episperm differed for their exclusive epicatechin, catechin, and proanthocyanidin dimer content. The novel data provide new insights into the differences in the chemical compositions of byproducts of these hazelnut cultivars, which will be valuable for nutraceutical, cosmetic, and functional food valorisation applications.