Abstract:

2,2,6,6-Tetramethyl-1-piperidinyloxy (TEMPO) was applied to catalyze the oxidation of konjac glucomannan
(KGM), which was selectively oxidized by sodium hypochloryte to 80% degree of oxidization (DO) yielding TEMPOoxidized
konjac glucomannan (OKGM). A microsphere delivery system that allowed the co-delivery of hydrophobic and
hydrophilic ingredients was prepared by cross-linking the carboxyl groups of TEMPO-OKGM polymers with ferric ions
through double emulsion cross-linking reaction which enabled the dissolution of β-carotene in the inner oil phase and
the absorption of anthocyanins to the polymer phase. Fourier transform infrared spectroscopic (FT-IR) results proved
the oxidation of the hydroxyl groups into carboxyl groups. The cell viability experiment showed that the OKGM polymer had
negligible cytotoxicity. The optimum conditions for OKGM microspheres preparation were as follows: OKGM concentration,
10%; mass ratio of cross-linker FeSO4 ·7H2O to polymer, 1:5; cross-linking time, 30 minutes; and reaction temperature, 35 ℃. The
size distribution of OKGM microspheres measured by dynamic light scattering was 20 to 40 μm, and the average diameter was
26.8 μm. The surface morphology of microspheres was observed by scanning electron microscopy and atomic force microscopy.
By confocal laser scanning microscopy, the distribution of hydrophobic and hydrophilic ingredients was observed simultaneously.
OKGM microspheres showed a great potential for delivering multiple nutrients.

Key words: konjac glucomannan, microspheres, bioactive ingredients, dispersibility, stability, intestine-specific, controlled release, microencapsulation