Production of a Protein Concentrate from Hazelnut Meal Obtained as a Hazelnut Oil Industry By-Product and Its Application in a Functional Beverage

Purpose: This study aimed to extract protein from hazelnut meal, to evaluate its functional properties, and to apply it in a functional beverage. Methods: Hazelnut meal protein (HMP) was extracted by isoelectric precipitation. Proximate composition as well as solubility and water and oil absorption capacities of HMP were evaluated. Functional beverages with 2% and 4% of HMP were produced and compared to a reference beverage in terms of physicochemical and sensory properties. Results: HMP with 86.8% protein was obtained. Essential amino acid concentration (36.65%) of HMP was considerably higher than many plant-based proteins. Moreover, branched-chain amino acids concentration composed of 12.33% of total protein. Water and oil absorption capacities of HMP was 2.21 ± 0.03 (g water/g protein) and 4.85 ± 0.28 (mL oil/g protein), respectively. 2% and 4% (w/v) HMP beverages (HMPB2 and HMPB4) were prepared and compared with the reference beverage (RB). All physiochemical properties investigated significantly differed except turbidity and viscosity. Sensory evaluation revealed that overall acceptability of the formulations was comparable to each other and that both HMPB2 and HMPB4 were preferred by the panelists. Conclusions: Results suggested that hazelnut meal can be a protein source for functional foods and partially replace the existing sources in a more environmentally friendly, cheap and sustainable manner. Graphic Abstract: [Figure not available: see fulltext.].