A Rapid Method of Ca-Alginate Microgel Particle Production and Encapsulations of Water-soluble and Water-insoluble Compounds via the Leeds Jet Homogenizer

Ca-alginate microgel particles have been extensively studied for use in various foods and in biomedical applications and are commonly produced using techniques, such as emulsification, prilling, microfluidic and spray-drying, which involve multiple processing steps, otherwise large particle sizes are yielded. This provides the motivation for this study: to produce the Ca-alginate microgel particles in a simple and rapid method via a Jet homogenizer developed by the University of Leeds School of Food Science and Nutrition. Furthermore, the aims are expanded to entrap water-soluble compounds (proteins and dyes) and water–insoluble compounds (polyphenols and β-carotene crystals). The results indicated that tuneable sizes of microgel particles could be obtained from the Jet Homogenizer. Various SEM techniques revealed the microgel particles of sizes below 50 nm forming clusters in microregions of size < 1 µm, thus sonication was applied to break down the aggregates. The microgel particle sizes could be controlled by altering the concentrations and viscosities of the alginate and by changing the fluid velocity. Rheological measurements were also employed to predict estimate the intrinsic viscosity ([η]) and MW of the elected alginate with low viscosity (LV) and to determine evaluate the apparent viscosity of the microgel suspensions over shear rates as a function of volume fraction (φ). These microgel particles were utilized to encapsulate water-soluble cationic proteins (lactoferrin and lysozyme) and dyes (anionic erioglaucine and cationic methylene blue). Lactoferrin had shown some adsorption to the microgel particles as demonstrated from the reduction of particle size as the ζ-potential was less negative. Successful loading of erioglaucine was achieved with high loading efficiency and payloads, but rapidly released due to high porosity of the microgel particles. Lysozyme and methylene blue did not show any adsorption or entrapment but rather formed complexations with the alginate instead. The water-insoluble particles of polyphenols and β-carotene were also successfully loaded into the microgel particles as revealed by the images obtained from confocal (CLSM) and the light microscopies. In short, the results have shown some firm evidence that Ca-alginate microgel particle formation and encapsulation of some the water-soluble and insoluble compounds within the Ca-alginate microgel particles can be achieved via this simple and effective technique.