Manufacture and characterisation of agarose microparticles

The mechanical properties of agarose microparticles formed by shearing bulk gels dispersed in cold water using a high speed rotor/stator device were investigated. The influence of agarose concentration on bulk gel texture (Young’s modulus, stress and strain at failure) and microparticle size (Sauter mean diameter and size distribution) was assessed. Results obtained showed that bulk gels from 1 to 8% (w/w) showed a linear increase in Young’s modulus with concentration, while the true strain values at failure levelled at high concentrations (>3%). High speed shearing of the bulk gels yielded final particle sizes for the l% and 2% w/w microgel suspensions significantly lower than for the more concentrated gels (3–8% w/w) which are statistically identical (p < 0.005) at 103 ± 2 μm, irrespective of concentration. Rheological investigation of the microparticle suspensions, over a range of bulk gel concentrations, showed that microparticles form a solid like suspension at high volume fractions, becoming fluid like above a well defined yield stress. Overall, a simple and low-cost procedure has been developed to produce an array of agarose microparticles that can confer a range of textural functionalities to beverages from liquids to fluid gels.