Bioactive, functional and edible film-forming properties of isolated hazelnut (Corylus avellana L.) meal proteins

• Protein isolates show antioxidant, anticancerogenic, antihypertensive activity.
• Good oil absorption and foaming are outstanding functional properties of isolates.
• Isolates have poor emulsifying, gelling and water absorption capacities.
• Acetone washing and hot extraction improve bioactive and functional properties.
• Hazelnut proteins form transparent, light to brown colored and flexible edible films.

This study aimed characterization of bioactive, functional and edible film making properties of isolated proteins from untreated (HPI), hot extracted (HPI-H), acetone washed (HPI-AW), and acetone washed and hot extracted (HPC-AW-H) hazelnut meals. The most bioactive protein extract was HPC-AW-H, followed by HPI-AW, HPI-H and HPI, based on antioxidant activity (TEAC and ORAC: 158–461 mmol Trolox/kg), iron chelation (60.7–126.7 mmol EDTA/kg), angiotensin-converting enzyme inhibition (IC50: 0.57–1.0 mg/mL) and antiproliferative activity on colon cancer cells (IC50: 3.0–4.6 mg/ml). Protein contents of HPI, HPI-H and HPI-AW (93.3–94.5%) were higher than that of HPC-AW-H (86.0%), but HPC-AW-H showed the best pH-solubility profile. The extracts showed good oil absorption (7.4–9.4 g/g) and foaming, but limited water holding and gelling capacities, and emulsion stability. The protein extracts gave transparent, yellowish to brownish and reddish colored and water soluble edible films. The HPI gave the lightest colored films with acceptable mechanical properties (elongation up to 144% and tensile strength up to 4.9 MPa). 1-D and 2-D electrophoresis clearly showed the molecular and isoelectric profiles of hazelnut proteins. The overall results of this study showed that the bioactive, solubility and gelation properties of hazelnut proteins could be improved by simple processes like acetone washing and/or heat treatment. The hazelnut proteins are valuable as multipurpose food ingredients.

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