Tailor-made encapsulation and delivery systems allow the incorporation of bioactive components into food matrices while preserving their chemical integrity and biofunctionality. Commonly used delivery systems include suspensions, gels, simple, multiple or multi-layered emulsions which are known to be thermodynamically unstable. Emulsifiers are useful in order to prepare kinetically stable emulsions under certain environmental conditions. The assembly of such systems is based on colloidal interactions that are strongly affected by environmental conditions including pH, temperature, and ionic strength. Colloidal systems undergo a variety of changes during production, transport, storage, and digestion leading to a breakdown or dissociation of the structure. The formation of covalent crosslinks between emulsifiers catalyzed by enzymes may offer a potential solution to this problem and provide for better long term stability of the generated structures. In this presentation, we will present results of three separate studies that taken together demonstrate that crosslinking enzymes such as laccase or transglutaminase may widen the functionality of emulsion-based systems in terms of pH-, salt-, temperature-stability. In multilayered emulsions stabilized by fish gelatin – beet pectin membranes, laccase promoted a crosslinking of adsorbed pectin improving its stability to changes in pH. Specifically, these emulsions were stable over a broad pH range from 3.5 to 10. Emulsions containing crosslinked fish gelatin - beet pectin coated droplets were also less prone to destabilization by Ostwald ripening, i.e. coated and crosslinked emulsions had lower droplet growth rates (3.1 ± 0.3 x 10-26 m3/s) than fish gelatin-stabilized droplets (7.3 ± 0.2 x 10-26 m3/s) which was attributed to a higher elasticity of membranes resisting shrinkage and growth. Finally, enzymatic crosslinking of emulsions also lead to modification of rheology at higher droplet concentrations, i.e. addition of enzymes led to droplet-droplet crosslinking rather than intra-membrane crosslinking when a critical oil volume concentration (coil > 0.6) was exceeded. Results of these studies thus show that rational use of crosslinking enzymes may enable food manufacturer to manufacture emulsions with improved physical, functional, textural, and rheological properties.
Principal investigator: Prof. Jochen Weiss j.weiss@uni-hohenheim.de
