Production of ultra-high concentration calcium alginate beads with prolonged dissolution profile

Abstract

Calcium alginate hydrogel beads have been widely studied as a carrier matrix for the delivery of food and pharmaceutical compounds. Typically, calcium alginate beads have a short dissolution time of between 1 to 2 h in simulated intestinal fluid, thus limiting some applications that require prolonged release of compounds. This study was aimed at fabricating calcium alginate beads with a prolonged dissolution profile by increasing the alginate concentration beyond the critical viscosity limit (approximately 5000 mPa s) that can be processed using the existing extrusion-dripping system. A temperature-controlled extrusion method was developed and the feasibility of producing alginate beads at ultra-high concentration (UHC) with an initial viscosity ranging from 33 000 mPa s to 353 000 mPa s was studied for the first time. The operating temperatures studied ranged from 40 °C to 80 °C. Spherical UHC alginate beads were successfully produced using an alginate solution with an initial viscosity of 33 000 mPa s. Fourier-transform infrared (FTIR) analysis indicated that the chemical properties of the alginate gels were not affected by the operating temperature. The dissolution time of the UHC alginate beads was three times longer than that of the beads produced using the normal alginate concentration. In addition, the UHC alginate beads have a unique internal structure that differs from the normal beads. In conclusion, a facile method to produce the UHC alginate beads, without the need for chemical modification of the beads or/and additional processing steps, is demonstrated. The long dissolution time of the UHC alginate beads opens up windows of opportunity for applications in the sustained delivery of drugs and food ingredients.