Compositional Analysis and Sustainable Valorization of the Calabrian Hazelnut cv. ‘Tonda Calabrese’ and Its Processing Derivatives

Hazelnut cultivation is a strategic agricultural sector in Italy, with Calabria contributing through the native "Tonda Calabrese" cultivar, valued for its biodiversity. Despite its importance, data on the nutritional and compositional characteristics of this cultivar remain limited. In this study, hazelnuts from three different Calabrian producers were analyzed for morphological traits, proximate composition, and elemental content, using both conventional and non-destructive techniques such as CIELab color profiling and ATR-FTIR spectroscopy. The nuts showed high levels of essential micro-elements (Fe, Cu, Zn), aligning with previous findings on other cultivars, and showed no detectable pesticide residues, confirming their nutritional quality. Moreover, this study also aims to explore sustainable valorization strategies for hazelnut by-products, embracing circular economy principles in a "zero waste" approach, including oils and defatted flours. The extracted oils were evaluated for oxidative stability (peroxide value, p-anisidine, TOTOX index) and acidity, meeting Codex Alimentarius quality standards. The residual defatted flour was upcycled through eco-friendly methods, such as Ultrasound-Assisted Extraction (UAE) and Enzyme-Assisted Extraction (EAE), to isolate the polyphenol and protein fractions, respectively. Both extracts exhibited notable antioxidant activity (34.7-35.3 mmol Fe²⁺ eq/100 g and 64.3-82.2 mmol Fe²⁺ eq/100 g, respectively), suggesting their potential use as valuable ingredients for dietetic and nutraceutical applications.