Encapsulation of lipid by alginate beads reduces bio-accessibility: An in vivo 13C breath test and MRI study

This paper describes an in vivo study of the use of encapsulation to alter lipid bio-accessibility in the gastro-intestinal (GI) tract. The hypothesis that encapsulation would delay the accessibility of lipid in the GI tract was tested using subjects (N = 11) who consumed either 30 g of 13C-labelled sunflower oil encapsulated within 70 g alginate gel particles, or unencapsulated ‘free’ sunflower oil and alginate-only particles (control). Lipid accessibility was determined by the appearance of the 13C label in breath carbon-dioxide (CO2), and the particles behaviour in the GI tract was investigated using non-invasive magnetic resonance imaging (MRI). Despite apparently faster gastric emptying, encapsulation of lipid resulted in a mean 47 min delay in the time to peak of the 13C label reaching the breath and a reduction in the initial slope of the 13C breath curve (both p < 0.05). Furthermore the gall bladder ejection fraction measured from MRI data was significantly smaller for the encapsulated lipid meal. We suggest this was due to delayed accessibility of the lipid for its digestion to the free fatty acids which are required to stimulate duodenal receptors and the release of cholecystokinin (CCK). This would account for both the smaller gall bladder response and faster gastric emptying observed with the encapsulated lipid meal. This study showed that encapsulation is an effective strategy to control the GI fate of lipids. It also showed that multimodal studies including MRI are powerful tools for investigating how the body handles food components and may aid in the design of food products with controlled functionality.