Particle Size and Sphericity of Alginate-pectin Hydrogel Particles Produced by Vibration-extrusion

Anna McSurley and Justyna Korneluk
Undergraduate (Food Science)
Dr. Gonul Kaletunc
Food, Agricultural and Biological Engineering

In the food industry there is a need for bioactive components to be encapsulated in edible matrices. Encapsulation is applied to protect bioactive compound, to mask a sensory property, or control the release of the active ingredient at the intended target in the body. The particle size and shape affect kinetics of particle dissolution and release of the active ingredient. The objectives of the study are to determine the operating parameters to produce hydrogel spherical particles via vibration-extrusion; and to characterize the effect of nozzle size and particle production parameters on particle size distribution and shape as evaluated by sphericity (Sp). The results will lead to development of models to predict particle size and shape desired for specific applications. The alginate-pectin hydrogel particles were produced by extrusion technique assisted with vibration using an encapsulator unit (BUCHI-390, BUCHI, Flawil, Switzerland). The nozzle diameter (80, 120, 150, 200, 300, 450 μm), the frequency of vibration (180-1600 Hz), and the pressure (400-700 mbar) were varied while the total gum concentration of hydrogel solution (1.1%wt), the solution flow rate (0.05 g/s) and the voltage applied to the gelling bath (500 V) were kept constant. The particle size was determined by using Image J software from photographs obtained with a microscope at 10X or 60X magnifications. Top and side view orientations were taken to calculate sphericity. Average particle size increased from 374.5± 108.8 µm for a 120 µm nozzle at 1600 Hz frequency to 1256 ± 112.3µm for a 450 µm nozzle at 180 Hz frequency. The hydrogel particles closest to a sphere (Sp<0.05) was obtained with at a Sp value of 0.086 with a 200 µm nozzle at and a frequency of 900 Hz. The results indicate that the average particle size increases over a wide distribution with increasing nozzle opening. The particle size is also affected by the frequency of vibration for a given nozzle. These findings are significant in determining optimal parameters for producing the desired particle sizes and shapes for a specific application, such as the production of slow- versus fast-release hydrogel particles.