•OKGM polymers offer a new option for preparing vegetarian hard capsules.•OKGM hard capsules were satisfactorily qualified for gastric soluble capsules.•OKGM of higher DO is superior to prepare hard capsule than OKGM of lower DO.TEMPO-oxidized Konjac glucomannan (OKGM) was developed as new material for preparing vegetarian hard capsules. OKGM of different degrees of oxidation: DO30%, DO50%, and DO80% were prepared to select optimum DO for capsule formation. FT-IR results proved that the primary alcohol groups on KGM were oxidized into carboxyl groups. XRD analysis suggested that TEMPO-oxidation decreased the crystallinity of KGM. DO80% was considered as the optimum candidate for capsule preparation owing to its superior solubility, transparency and reduced viscosity. The hydrophilicity of OKGM films, measured by contact angle measurement, increased with increasing DO. The elongation at break and tensile strength of the OKGM films enhanced with increasing DO. In vitro drug dissolution profile of OKGM capsules showed that the shell rupture time of DO80% capsule is about 5–10 min, and 80% of the drugs were released within 30–45 min. Thus DO80% OKGM was qualified to be used for gastric soluble hard capsules.

•The natural potato starch based microgels have well-defined properties.•The responsive oxidized starch microgel is suitable for controlled uptake release.•The protein binding by microgel is mainly determined by charge compensation.A biodegradable microgel system based on glycerol-1,3-diglycidyl ether (GDGE) cross-linked TEMPO-oxidized potato starch polymers was developed for controlled uptake and release of proteins. A series of microgels were prepared with a wide range of charge density and cross-link density. We found both swelling capacity (SWw) and lysozyme uptake at saturation (Γsat) increased with increasing degree of oxidation (DO) and decreasing cross-link density. Microgel of DO100% with a low cross-link density (RGDGE/polymer (w/w) of 0.025) was selected to be the optimum gel type for lysozyme absorption; Γsat increased with increasing pH and decreasing ionic strength. It suggests that the binding strength was the strongest at high pH and low ionic strength, which was recognized as the optimum absorption conditions. The lysozyme release was promoted at low pH and high ionic strength, which were considered to be the most suitable conditions for triggering protein release. These results may provide useful information for the controlled uptake and release of proteins by oxidized starch microgels.

An intestine-specific delivery system for hydrophobic bioactives with improved stability was developed. It consists of oxidized potato starch polymers, where the carboxyl groups were physically cross-linked via ferric ions. The model hydrophobic ingredients (β-carotene) were incorporated inside the starch microspheres via a double-emulsion method. Confocal laser scanning microscopy images showed that β-carotene were distributed homogeneously in the inner oil phase of the starch microspheres. The negative value of the ζ-potential of microspheres increased with increasing pH and decreasing ionic strength. In vitro release experiments showed that the microspheres were stable at acidic stomach conditions (pH < 2), whereas at neutral intestinal conditions (pH 7.0), they rupture to release the loaded β-carotene. The 1,1-diphenyl-2-picrylhydrazyl radical, 2,2-diphenyl-1-(2,4,6-trinitriphenyl), scavenging activity results suggested that microsphere-encapsulated β-carotene had an improved activity after thermal treatment at 80 °C. The storage stability of encapsulated β-carotene at room temperature was also enhanced. The starch microspheres showed potential as intestine-specific carriers with an enhanced stability.

•It is the first study of thermal cross-linked WPI NPs in Pickering emulsions.•Heat-resistant WPI NPs allow their use in applications requiring heat treatment.•WPI NPs have good partial wetting properties for stabilizing o/w emulsions.•WPI NPs can produce stable o/w emulsions at pH above and below the WPI NP's pI.A Pickering (o/w) emulsion was formed and stabilized by whey protein isolate nanoparticles (WPI NPs). Those WPI NPs were prepared by thermal cross-linking of denatured WPI proteins within w/o emulsion droplets at 80 °C for 15 min. During heating of w/o emulsions containing 10% (w/v) WPI proteins in the water phase, the emulsions displayed turbid–transparent–turbid phase transitions, which is ascribed to the change in the size of the protein-containing water droplets caused by thermal cross-linking between denatured protein molecules. The transparent stage indicated the formation of WPI NPs. WPI NPs of different sizes were obtained by varying the mixing speed. WPI NPs of 200–500 nm were selected to prepare o/w Pickering emulsions because of their good stability against coalescence. By Confocal Laser Scanning Microscopy, it was observed that WPI NPs were closely packed and distributed at the surface of the emulsion droplets. By measuring water contact angles of WPI NPs films, it was found that under most conditions WPI NPs present good partial wetting properties, but that at the isoelectric point (pI) and high ionic strength the particles become more hydrophobic, resulting in less stable Pickering emulsion. Thus, at pH above and below the pI of WPI NPs and low to moderate ionic strengths (1–10 mM), and with a WPI NPs concentration of 2% (w/v), a stable Pickering emulsion can be obtained. The results may provide useful information for applications of WPI NPs in environmentally friendly and food grade applications, notably in food, pharmaceutical and cosmetic products.

A light-responsive delivery system has been developed. It consists of gelly microspheres made of TEMPO-oxidized Konjac glucomannan (OKGM) polymers where the carboxyl (COO–) groups are cross-linked via ferric ions (Fe3+) and in which functional ingredients may be incorporated. By irradiation with (simulated) sunlight, the microspheres degrade, thereby releasing the encapsulated component(s). The degree of oxidation (DO) of the OKGM polymers could be well-controlled between 15 and 80%, as confirmed by proton titrations and FT-IR spectroscopy. OKGM of DO 80% was selected to prepare the microspheres because the high COO– content leads to a high density of cross-links, yielding a strong gel. The electrokinetic potential of the OKGM particles increases with increasing pH and decreasing salt concentration. Mössbauer and FT-IR spectroscopy revealed that the cross-links are formed through two modes of COO––Fe3+ coordination, that is, 68.4% by bridging and 31.6% by unidentate binding. Thus, the unique properties of the OKGM microspheres make them potentially applicable as light-controlled biocompatible delivery systems.