Optimization of genistein solubilization by κ-carrageenan hydrogel using response surface methodology

κ-Carrageenan was explored to improve genistein solubility by matrix retention. The corresponding maximum value in the efficiency of retention (Re) (50.48 mg/100 mg) was achieved when variables were set as: pH 4.76, temperature 52.12 °C and genistein concentration 0.27 mg/mL. The coefficient of determination (R2) of the response surface regression model presented in this study was 0.9848. The evidences from XRD, DSC and FT-IR attested the amorphous form of genistein in hydrogel matrix. Importantly, the solubility of genistein in hydrogel amorphous form (16.84–34.42 μg/mL) was much higher than that of its free crystalline form (1.89–6.09 μg/mL) over 30–90 °C.