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In situ monitoring of lipid droplet release from biopolymer microgels under simulated gastric conditions using magnetic resonance imaging and spectroscopy

Zhang, Zipei, Jung, Kwan-Jin, Zhang, Ruojie, Muriel Mundo, Jorge L., McClements, David Julian
Food research international 2019 v.123 pp. 181-188
alginates, bioavailability, biopolymers, blood, carrageenan, droplets, energy intake, food composition, functional foods, gastric juice, in vivo studies, light microscopy, lipids, magnetic resonance imaging, magnetism, microgels, monitoring, nutrient content, proteins, spectroscopy, stomach, turbidity
Functional foods are being designed to breakdown in the human gut in a controlled fashion so as to regulate blood nutrient profiles, hormone release, energy intake, and bioavailability. Biopolymer microgels, small spherical beads made from proteins and/or polysaccharides, are a promising tool that can be used to modulate the gastrointestinal behavior of food components. In this study, lipid droplets were loaded into microgels fabricated from either alginate or carrageenan using an injection-gelation method. The lipid-loaded microgels were then incubated in simulated gastric juices and the impact of biopolymer type on the release of the lipid droplets was observed. Optical microscopy and turbidity measurements showed that lipid droplet release occurred more rapidly for the carrageenan microgels, which was attributed to their partial disruption in the gastric fluids. In contrast, lipid droplet release was relatively slow from the alginate microgels because they remained intact. We also showed that magnetic resonance imaging (MRI) could be used for in situ monitoring of carrageenan microgel disruption and lipid droplet release under simulated stomach conditions. This method was based on quantifying the local lipid levels using T1 images and the magnetic resonance spectroscopy. A water-selected VIBE sequence was optimized for obtaining the T1 images and a stimulated echo acquisition mode (STEAM) sequence was selected for obtaining the MR spectra. The MRI method may be particularly useful for in vivo studies of the behavior of filled microgels.