Maillard-Type Cross-Linked Soy Protein Hydrogels as Devices for the Release of Ionic Compounds: An In Vitro Study

The contribution of cross-linking degree on soy protein hydrogels release properties was studied in vitro using a Maillard-type cross linker and amaranth and methylene blue as tracers. Increased cross-linker concentration or salt presence in the gel generally led to decreased swelling/release rates in the absence of digestive enzyme. Surprisingly, at pH 1.2, amaranth was not released. In the presence of pepsin or pancreatin, increased cross-linker concentration or the presence of salt in the gel was also shown to decrease compound release, particularly for methylene blue at pH 7.5. Compound release was strongly dependent on medium pH and compound ionic status. Amaranth, an anionic molecule, showed slower release in gastric conditions, whereas methylene blue, a cationic drug, showed the opposite result. Partition coefficients of these compounds matched these results. This paper demonstrates the potential of food proteins as carriers of ionic compounds.