Effect of ultrasound treatment on the properties of nano-emulsion films obtained from hazelnut meal protein and clove essential oil

Abstract

Hazelnut meal protein (4% (w/v)) and clove essential oil (CEO) (3% (v/v)) were homogenized with ultrasound (US) at different times (2, 4 and 6 min) and amplitudes (50, 75 and 100%) to obtain nano-emulsion films. Film forming nano-emulsions (FFNs) were analyzed for average particle size (Dz) and zeta potential, and edible film characterization were evaluated depending on US treatment, as well as antibacterial and antioxidant activities. Dz values and zeta potential of FFNs decreased with increasing acoustic energy delivered to nano-emulsion system. Thickness and water solubility of films significantly decreased with increasing US treatment. Films became more transparent depending on US treatment probably due to particle size reduction. Tensile strength (TS) of films significantly increased with US treatment, while elongation at break (EAB) slightly increased. Microstructure of films became more homogeneous after US treatment and caused to lower water vapor permeability. Enrichment with CEO has given the films antibacterial activity against L. monocytogenes, B. subtilis, S. aureus, P. aeruginosa and E. coli, and antioxidant activity, and US application has improved these activities. US technology can be used to improve mechanical, barrier and antimicrobial properties of hazelnut meal protein based edible films enriched with CEO.