Development of Pea Protein Films with Haskap (lonicera Caerulea) Leaf Extracts from Aqueous Two-phase Systems

Pea protein films were developed using haskap (Lonicera caerulea) leaf extracts obtained from aqueous two-phase extraction (ATPE) and aqueous two-phase flotation (ATPF), where the components from the aqueous two-phase systems were incorporated directly into the films. The films were formulated with components that were GRAS (Generally Recognized as Safe): either pea protein isolate (PPI) or pea protein concentrate (PPC), glycerol as plasticizer, carboxylic acids (citric acid or malic acid) as cross-linkers, and the haskap leaf extracts comprising of bioactive compounds, ethanol, salt (sodium phosphate or ammonium sulphate), and water. Films were produced by the bench casting method, and they were assessed in terms of physical, mechanical, optical, water vapour permeability, thermal, migration, and antioxidant properties. Some formulations with the haskap leaf extracts demonstrated better water vapour permeability and flexibility with the presence of salt. The films also exhibited thermal stability as the melting temperatures were higher than 150 °C and ultraviolet absorption properties that would protect products from ultraviolet degradation. Additionally, the films allowed the migration of bioactive compounds into alcoholic and fatty food simulants, which suggests that they could extend the shelf life of perishable food and increase the antioxidant properties of the packaged products. This work also shows that post-extraction steps such as alcohol evaporation and salt precipitation are not necessary with aqueous two-phase systems and could therefore reduce associated processing costs.