Abstract
In the food industry the use of proteins-polysaccharides complexes and coacervates in developing the food application received an increased attention in the recent years. The application towards e.g. food ingredients, biomaterial, and in the systems of (bio)active components are some examples where biopolymer complexes and coacervates are being used. Proteins-polysaccharides formation and their interactions is influenced by chemical and physical parameters. In food applications the components and their functional properties can be controlled and manipulated to achieve the required properties to upgrade the food packaging and applications in the food industry (Ye, 2008). The pH, ionic strength, biopolymer ratio, total polymer concertation, charge density and temperature are some of the factors that can be investigated and controlled.
In this study, alginate and casein were used to investigate the protein-polysaccharide formation under different parameters. Alginate is a carboxylated polysaccharide which is extracted from brown macroalgae. Alginate can form complexes with metal cations, which in this study sodium casein were used. On the other hand, casein is a milk protein which has a wide use for research and is a component with increased usage for delivery systems and food applications. The derived sodium casein from casein was used in this study for protein-polysaccharide complex and coacervate analyzes.
The investigations showed that the electrostatic interactions give the biopolymer complexes their solubility properties. Under different conditions, the formation of soluble and insoluble complexes is observed. Complex coacervation is obtained when phase separation occurred. In the screening experiment, a specific range of NaCa/Alg and total biopolymer concentration were studied. From the results obtained, a total biopolymer concentration constant at 0.5% were used for further analyzing. The results obtained showed that the formation of complex coacervation is mainly pH and biopolymer ratio influenced. In addition, the analyses such as zeta potential, particle size and polydispersity index showed decreasing and increasing trends mainly depended on the charge density, pH, and biopolymer ratio. The physicochemical factors determine the formation and stability of the protein-polysaccharide complexes as it is revealed in this study which lead to identifying relevant food applications.