Whey protein gels for the entrapment of bioactive anthocyanins from bilberry extract

A matrix system on the basis of thermally induced strongly acidic whey protein isolate gels for the encapsulation of anthocyanin-rich bilberry extract (BBE) was developed. Appropriate heating conditions required for the generation of BBE-loaded water-insoluble gel systems from protein solutions were determined. Release kinetics of anthocyanins were evaluated in simulated gastric fluid. Data indicated that entrapped anthocyanins were released from the gels by Fickian diffusion. The release rate constant k and the diffusional exponent n were influenced by protein content and bilberry extract load. In this context pH-dependent interactions between whey proteins and BBE-constituents were identified, which had a detrimental effect on the gelation characteristics, stability and release characteristics of the gel systems at pH 3. However, it could be shown that encapsulation of bilberry extract in whey protein gels at pH 1.5 lead to stronger stabilisation than in gels at pH 3 due to the known pH-dependency of anthocyanin stability.