Characterization of rosemary and thyme extracts for incorporation into a whey protein based film

Active packaging is designed to interact with foods by releasing active components with biological properties, allowing the extension of foods shelf-life, being aromatic plants a source of active compounds. The main goal of this research was to develop a biodegradable whey protein based film, incorporated with an aromatic plant extract. Ethanolic extracts from rosemary and thyme were obtained from three commercial brands. The DPPH
- scavenging activity assay showed that the rosemary extracts presented the highest antioxidant capacity. Thyme acetone extract had the highest antioxidant activity in the β-carotene bleaching assay. Three different mixtures of rosemary and thyme extracts with the highest antioxidant capacity showed a lower antioxidant capacity than the single extracts. The content of carnosic acid, carnosol and rosmarinic acid was determined in the three rosemary extracts, having the extract from the brand C shown the highest phenolics content. The extract showed antimicrobial activity against Staphylococcus aureus, Listeria monocytogenes and Clostridium perfringens. For the active film, 1% of the rosemary extract was incorporated into the whey protein film. The film presented antimicrobial activity against L. monocytogenes and S. aureus.