Physical and Chemical properties (permitivitty spectra in radiofrequency range, moisture, water activity, image analysis) of the gastric and intestinal digestion of galic acid encapsulated in calcium alginate

Inflammatory bowel disease (IBD) is a widespread clinical condition, which imposes a significant economic burden. The consumption of gallic acid (GA) is an effective alternative therapy to alleviate the symptoms of IBD, thanks to its pharmacological properties. Encapsulation of bioactive compounds in a calcium alginate matrix enhances their bioavailability and enables a targeted release. To assess the release kinetics of encapsulated bioactive compounds during digestion, a continuous, novel and quantitative method based on  permettivity measurements can be successfully employed. In this work, GA was encapsulated in a calcium alginate matrix by extrusion. The swelling of the system in simulated gastric medium (SGM) and simulated intestinal medium (SIM) was analyzed by optical microscopy, and the release kinetics of the bioactive compound in both digestive phases was obtained through radiofrequency spectroscopy. An irreversible thermodynamic model was developed to elucidate the main driving forces involved in GA release in SGM and SIM. The results showed that the calcium alginate matrix effectively limit GA release in gastric phase, enabling its maximal release at the intestinal level, where the neutral pH and electrolyte exchange promote GA diffusion.