Hake proteins edible films incorporated with essential oils: Physical, mechanical, antioxidant and antibacterial properties

Physical, mechanical, antioxidant and antimicrobial properties of hake protein films incorporated with citronella, coriander, tarragon and thyme oils were investigated. Dried hake proteins were solubilized at pH 11.0 (protein concentration in film forming solution ca. 0.9%) and glycerol (59% w/w of protein) and 0.25 ml of each essential oil per gram of protein was added. Films obtained were homogeneous and transparent with a yellowish colour. The addition of the different essential oils reduced the water vapour permeability but increased the solubility of films in water. The amount of protein released from the films depended on the oil added. Among all essential oils incorporated-films the thyme oil films exhibited the lowest mechanical properties (puncture force and elongation at break). Conversely, films with thyme oil added presented the highest inhibition against Shewanella putrefaciens. Antioxidant activity of hake protein films generally increased with the incorporation of essential oils as indicated by DPPH radical scavenging activity and reducing power.

Figure optionsDownload as PowerPoint slideHighlights
► Transparent biodegradable films were successfully prepared from hake protein powder and essential oils.
► Addition of essential oils reduced water vapour permeability.
► Essential oils with the exception of thyme oil did not affect the mechanical properties.
► Hake protein films exhibited antioxidant activity, which was improved by the addition of the essential oils.
► Films with thyme oil reduced S. putrefaciens in one logarithmic unit.