The impact of HPMC structure in the modulation of in vitro lipolysis: The role of bile salts

Abstract

The behaviour of two hydroxypropylmethylcelluloses (HPMC), with different molecular structures: E5LV and E4M, has been analysed in the presence of the bile salts, both at the oil-water interface (emulsion behaviour, interfacial properties and ζ-potential) and in the aqueous medium (particle size distribution analysis, cloud point temperature and electrical conductivity). HPMCs emulsions experienced different degrees and rate of lipolysis (E4M emulsions experienced a higher lipid digestion than emulsions stabilized by E5LV) that were not related to differences in the molecular weight/viscosity. Differences in the kinetics of lipolysis can be attributed to the interaction with BS according to methyl/hydroxypropyl ratio of these HPMCs. The self-assembly of the E4M cellulose, being the more hydrophilic cellulose (with a lower methyl/hydroxypropyl ratio than E5LV) was more hindered by the bile salts adsorption, thus developing a higher untangling at the interface that would increase the available sites for the lipase. These results allow a better understanding of the mechanisms that affect food emulsions digestion and it could allow to design polysaccharides stabilized emulsions with better functional properties.