In vitro digestion and faecal fermentation of starch-lipid complexes with distinct crystalline forms prepared by extrusion-cooking.

Complexes were prepared between maize starch (MS) and lauric acid (LA) by extrusion-cooking and the in vitro digestion and fermentation properties of complexes containing only VI-type or VII-type crystallites were investigated. The formation and structure of complexes were largely dependent on the parameters of extrusion conditions. Under certain extrusion conditions, MS-LA complexes with only VI-type or VII-type crystallites were prepared. In vitro enzymatic digestion showed that MS-LA complexes, especially the VII-type complex, had lower susceptibility to amylolysis than the corresponding extruded MS. In vitro fermentation of complexes residues after digestion led to altered microbial communities and production of greater amounts of short-chain fatty acids (SCFAs) compared to the corresponding extruded starches and fructo-oligosaccharide (FOS). Notably, more SCFAs (particularly butyrate) were generated by fermentation of VII-type complexes than by fermentation of VI-type complexes, which was explained as being due to the greater growth of the SCFA-producing bacteria Megasphaera, Blautia, Agathobacter and Subdoligranulum. This study clearly showed that starch-lipid complexes with different crystalline forms can be prepared by extrusion-cooking, and that the more ordered VII-type complexes had the potentially better prebiotic functions than the less ordered VI-type complexes.