Complex coacervation of whey proteins to design biocarriers for bioactives
Résumé
Bioactives such as vitamins are often very sensitive to conditions applied during food processing and storage. The design of carriers for the protection and controlled delivery of such bioactives represents a challenge for developing functional foods. Yet, consumers tend to favor food products with minimal amount of external additives. Then, it appears relevant to use directly some components of the targeted food product as biocarrier materials for bioactives. Here, we investigated the potentiality of two whey proteins, Beta-lactoglobulin (BLG) and Lactoferrin (LF), known for their capacity of complex coacervation1, to spontaneously co-assemble with a vitamin having a crucial biological role: the vitamin B9.
Across a range of B9:Proteins mixing ratios and pH conditions, B9-LF-BLG co-assemblies were obtained and assessed by turbidity and phase contrast microscopy. Kinetics of their formation were monitored by multiple light scattering. B9 entrapment was evaluated. Size and shape of co-assemblies were characterized by dynamic image analysis. Storage and time stability of co-assemblies were assessed at 4°C and 20 °C over time.
Two types of B9-LF-BLG co-assembly were identified: aggregates (at low and high protein concentrations), and coacervates (at intermediate protein concentrations), both exhibiting different formation kinetics over time. Plotting screening maps of B9-LF-BLG co-assemblies and B9 entrapment efficiencies, we evidenced that B9-LF-BLG coacervates exhibited higher performance as B9 biocarrier, with an optimal entrapment of ≈ 10 mg B9/g Proteins. B9-LF-BLG coacervates showed a mean diameter of 10 µm. The dense phase of B9-LF-BLG coacervates were stable over a two weeks storage at 4°C and 20°C, without any detectable degradation of B9. Working volume also showed a great impact on the recovered dense phase of coacervates and its stability.
The entrapment efficiency of B9 by B9-LF-BLG coacervates was found to be similar to that of other encapsulation technology such as spray drying2. Few mg of coacervates can cover the recommended daily intake of B9. Thus, these heteroprotein systems display useful potentialities as biocarriers for bioactives. Their formation requires minimal energy input and involves co-products of the dairy industry. They constitute new structured biopolymer-based delivery systems with enhanced health benefit to formulate natural and functional ingredient.