Soy protein cold-set hydrogels as controlled delivery devices for nutraceutical compounds

The release of riboflavin from soy protein hydrogels of filamentous or particulate microstructure was investigated under gastric and intestinal conditions in the presence or absence of digestive proteases. Microscopic examination showed riboflavin arranged into crystals dispersed randomly throughout the gels. Rheological analysis revealed that the riboflavin load weakened the gel networks, which led to gel disintegration during hydro-swelling tests at pH 7.5. Dissolution tests showed that riboflavin release was faster at pH 7.5 than at pH 1.2 for both gels. Initial release was faster from particulate gels, due to their higher porosity and eroding granular texture. The release mechanisms involved in riboflavin release were diffusion and matrix degradation for both gels at pH 1.2 and pH 7.5. In the presence of pepsin at pH 1.2, both gel types provided good protection of riboflavin for at least 6 h, while both were digested in the presence of pancreatin at pH 7.5. These results suggest that both gels might be useful for transporting bioactive molecules through the gastrointestinal tract and delivering them in the small intestine. Considering their non-synthetic nature, they should be of great interest to developers of innovative functional foods.