Release from what? Mostly for In-vivo systems people can target free curcumin circulating in plasma or its by product while in-Vitro systems one can use UV spectra's or HPLC.
Some useful references:
The Chemistry of Curcumin: From Extraction to Therapeutic Agent
You can use the surfactant in the release medium for hydrophobic drug release study you can follow this article
Self-Assembly of Partially Alkylated Dextran-graft-poly [(2-dimethylamino) ethyl methacrylate] Copolymer Facilitating Hydrophobic/Hydrophilic Drug Delivery and Imp...