The feasible methods of stabilization within the constraints of retaining natural status:
Complex formation: Anthocyanin occurs naturally as complexes which are relatively stable. Studies on pectin/anthocyanin complexes may be useful.
Co-pigmentation: In formulating a product containing anthocyanin colourants, the inclusion of a co-pigment would augment and stabilize the colour.
Condensation: This seems the most likely way of producing acceptable, natural colourants for the reasons stated previously. Considerable research to study the production of the polymeric colours and their stability in food products needs to be carried out.