Hydrogel beads (microgels) are promising delivery systems for encapsulation and release of proteins because they can be fabricated from food-grade biopolymers using mild processes. In this study, a model globular protein (whey protein) was encapsulated in calcium-alginate beads (D 43 = 290 to 520 μm) fabricated using an extrusion device with a vibrating nozzle. Protein-loaded beads were fabricated at three different pH values (pH 3, 5 and 7) to study the influence of protein-alginate electrostatic interactions on protein encapsulation, retention, and release. Protein encapsulation and retention was highest at low pH, while protein release was highest at high pH. Confocal microscopy and spectrophotometry measurements indicated that increasing the pH could trigger protein release from alginate beads formed at pH 3. These results suggest that hydrogel beads are suitable for encapsulation and pH-triggered release of proteins, which may be advantageous for certain food applications.

Encapsulation of enzymes in hydrogel beads may improve their utilization and activity in foods. In this study, the potential of carrageenan hydrogel beads for encapsulating β-galactosidase was investigated. Hydrogel beads were fabricated by injecting an aqueous solution, containing β-galactosidase (26 U) and carrageenan (1 wt%), into a hardening solution (5% potassium chloride). Around 63% of the β-galactosidase was initially encapsulated in the hydrogel beads. Encapsulated β-galactosidase had a higher activity than that of the free enzyme over a range of pH and thermal conditions, which was attributed to the stabilization of the enzyme structure by K(+) ions within the carrageenan beads. Release of the enzyme from the beads was observed during storage in aqueous solutions, which was attributed to the relatively large pore size of the hydrogel matrix. Our results suggest that carrageenan hydrogel beads may be useful encapsulation systems, but further work is needed to inhibit enzyme leakage.

24Delivery systems are needed to protect carotenoids in foods, but release them at an 25 appropriate location within the gastrointestinal tract (GIT). In this study, β-carotene was 26 incorporated into three different delivery systems: free lipid droplets; filled hydrogel 27 beads formed using 0.5% alginate ("0.5% beads"); and, filled hydrogel beads formed 28 using 1% alginate ("1% beads'). Hydrogel beads were fabricated by injecting an alginate 29 solution into a calcium ion solution using an extrusion device (Encapsulator). Light 30 scattering and confocal microscopy measurements indicated that the 0.5% beads had 31 much smaller diameter (285 μm) than the 1% beads (660 μm). β-carotene encapsulated in 32 free lipid droplets (nanoemulsions) was highly unstable to chemical degradation when 33 stored at elevated temperatures. Conversely, incorporation of the β-carotene-loaded 34 lipid droplets into hydrogel beads greatly improved its chemical stability. Simulated GIT 35 studies indicated that the rate and extent of lipid digestion decreased in the following 36 order: free lipid droplets >0.5% beads > 1% beads. The encapsulated β-carotene had a 37 higher bioaccessibility in free lipid droplets than in hydrogel beads, whereas its chemical 38 stability within the GIT was higher in the hydrogel beads, with the 1% beads giving 39 better protection against degradation than the 0.5% beads, which was attributed to 40 differences in hydrogel pore size. Overall, our results provide valuable information for 41 the rational design and development of nutraceutical delivery systems for utilization in 42 functional food products. 43

Knowledge of the physicochemical properties of ingestible silver nanoparticles (AgNPs) in the human gastrointestinal tract (GIT) is essential for assessing their bioavailability, bioactivity, and potential health risks. The gastrointestinal fate of AgNPs and silver ions from a commercial dietary supplement was therefore investigated using a simulated human GIT. In the mouth, no dissolution or aggregation of AgNPs occurred, which was attributed to the neutral pH and the formation of biomolecular corona, while the silver ions formed complexes with biomolecules (Ag-biomolecule). In the stomach, aggregation of AgNPs did not occur, but extensive dissolution was observed due to the low pH and the presence of Cl. In the fed state (after meal), 72% AgNPs (by mass) dissolved, with 74% silver ions forming Ag-biomolecule and 26% forming AgCl. In the fasted state (before meal), 76% AgNPs dissolved, with 82% silver ions forming Ag-biomolecule and 18% forming AgCl. A biomolecular corona around AgNPs, comprised of mucin with multiple sulfhydryl groups, inhibited aggregation and dissolution of AgNPs. In the small intestine, no further dissolution or aggregation of AgNPs occurred, while the silver ions existed only as Ag-biomolecule. These results provide useful information for assessing the bioavailability of ingestible AgNPs and their subsequently potential health risks, and for the safe design and utilization of AgNPs in biomedical applications.

The influence of plant-based (gum arabic and quillaja saponin) and animal-based (whey protein isolate, WPI) emulsifiers on the production and stability of vitamin E-fortified emulsions was investigated. Their impact on lipid digestibility and vitamin bioaccessibility was also studied utilizing an in vitro gastrointestinal tract. WPI and saponin produced smaller emulsions than gum arabic. All emulsions had good storage stability at room temperature (4 weeks, pH 7). Saponin-and gum arabic-emulsions were resistant to droplet aggregation from pH 2 to 8 because these emulsifiers generated strong electrosteric repulsion. WPI-coated droplets flocculated around pH 5 due to a reduction in charge near their isoelectric point. Lipid digestion was slower in saponin-emulsions, presumably because the high surface activity of saponins inhibited their removal by bile acids and lipase. Vitamin bioaccessibility was higher in WPI-than in saponin-or gum arabic-emulsions. This information may facilitate the design of more efficacious vitamin-fortified delivery systems.