Characterization of the behavior of alginate-based microcapsules in vitro and in vivo

Functional formulations providing protection of nutritional products against gastric juice or a capable of delivering them to distinct areas of the gastrointestinal tract are increasingly utilized by the food industry. However, the application of functional excipients that are established in pharmaceutical applications is limited in case of food products, as they are typically not classified as Generally Recognized As Safe (GRAS).

Accordingly, we investigated whether two alginate-based microcapsule preparations (capsule diameter 1 - 2 mm) either based on alginate and maize starch (MS-type) or alginate and casein (OCF27-type) and both created from ingredients classified as food supplements provide functional properties with respect to regional gastrointestinal targeting.

For this purpose the in vitro disintegration and swelling of the microcapsules was tested in various media. Furthermore, individual microcapsules, magnetically labelled with 100 - 200 microg black iron oxide, were ingested by healthy volunteers under fasting and fed conditions. Gastrointestinal transit as well as the gastrointestinal disintegration behavior were determined by using Magnetic Marker Monitoring.

The results of in vitro and in vivo investigations show that both types of microcapsules are resistant to gastric juice for approximately 10 hrs under fasting and fed conditions. However, the disintegration characteristics of the two types of microcapsules within the intestines are different.

Whilst the MS-type of capsules disintegrated predominantly within the small intestine shortly after gastric emptying, the OCF27-type of capsules underwent a rather slow disintegration predominantly in the colon.