Characterization of a food-based enteric coating for capsules and its compatibility with an alternative sealing method

Efficiency of a new protein-based enteric coating for capsules was studied. Coating physical-chemical properties were compared to those obtained from a well-known methacrylate-based enteric coating (Eudragit). Swelling in simulated gastric fluid (SGF) was 20 times higher than for Eudragit films. Mechanical properties (elastic modulus, elongation and puncture strength at break) were comparable to those measured from a standard Eudragit formulation. Pilot-scale coating trials were performed following three methods: using a standard spray-gun configuration, using a HPC-based seal-coat prior to enteric coating and using an "inverted" spray-gun configuration. The effect of these methods on capsules sealing and in vitro gastric performance was studied. In vitro tests were performed following the two USP official methods: disintegration and dissolution. Inverted gun configuration and HPC-sealing showed the highest sealing efficiency and the best in vitro performance. Capsules with a weight gain of 14-16% generally passed all USP tests (no disintegration evidence after 60 min in SGF; release below 10% after 2h of experiments in SGF). However, in some cases, slight differences between results obtained from dissolution and disintegration tests were pointed out. This work demonstrates the potential of a protein-based enteric coating and underlines the importance of capsules sealing.