Development of Bio-based Films using Pea Protein and Haskap Leaf (Lonicera caerulea) Extracts from Aqueous Two-Phase Systems
Chong, Kar Yeen
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Haskap leaves (Lonicera caerulea) are an agricultural residue from haskap plants and are expected to become more abundant as interest grows in haskap berries as a commercial crop in Canada. Although haskap berries are mainly associated with health-promoting benefits, haskap leaves are also a source of bioactive compounds, such as chlorogenic acid (CGA) and flavonoids. The conventional extraction techniques used with biological materials present certain drawbacks such as the use of toxic solvents, high temperatures, and long extraction times. This thesis investigates aqueous two-phase systems (ATPS) for the recovery of bioactive compounds from haskap leaves and the development of novel biobased pea protein films. In view of possible food and health product applications, different ATPS comprised of generally recognized as safe (GRAS) components were studied: ammonium sulphate/ethanol, sodium dihydrogen sulphate/ethanol, glucose/1-propanol, and maltose/1-propanol. The results showed that salt/ethanol aqueous two-phase extraction (ATPE) had higher extraction efficiencies than sugar/propanol ATPE. Sodium dihydrogen phosphate/ethanol ATPE had maximum extraction efficiency at 93.9% for CGA, 96.8% for flavonoids, and 97.8% for total phenolic content (TPC). Recycling of the ATPE phase-forming components was also examined to increase the overall process sustainability and economics. With two recycling stages, the extraction efficiency of the ATPE systems were maintained. Aqueous two-phase flotation (ATPF) was then investigated with salt/alcohol systems by integrating air bubbles and ATPE. Ammonium sulphate/ethanol ATPF increased the partition coefficient from 9.6 to 29.6 for CGA, 23.1 to 62.4 for flavonoids, and 161.6 to 231.4 for TPC. Haskap leaf extracts obtained from ATPE and ATPF consisting of bioactive compounds, ethanol, water, and residual salt were then directly incorporated into pea protein films. Some film formulations with haskap leaf extracts showed improved water vapour permeability and flexibility. Pea protein isolate (PPI) films with sodium phosphate extracts showed the best potential for development as a packaging material for alcoholic and aqueous food products.