SPONTANEOUS FORMATION OF SMALL-SIZED ALBUMIN ACACIA COACERVATE PARTICLES

Microgel coacervate particles form spontaneously on mixing aqueous sol utions of oppositely charged albumin and acacia, under specific condit ions of pH. ionic strength, and polyion concentration, close to but no t at the optimum conditions for maximum coacervate yield. The mean par ticle diameter of these coacervate particles is approximately 6 mum wh en suspended in aqueous media, as determined by HIAC/Royco particle an alysis. The geometric standard deviation of the particles falls in the range 1.2-1.9 mum. The particle size was not dependent on the method of emulsification of the coacervate in the equilibrium phase, or on th e stirring speed applied during the manufacturing process. The microge l particles were stable on storage, for periods up to forty-six days, without the addition of a chemical cross-linking agent, or the applica tion of heat. Stability was measured with respect to the change in par ticle size of samples stored at different temperatures. The non-cross- linked microcapsules were also shown to be stable on pH change, to pH values outside the coacervation pH range. At the optimum conditions fo r maximum coacervate yield the albumin/acacia system formed a very vis cous coacervate phase. which was unsuitable for microcapsule preparati on. The rheological properties of albumin/acacia and gelatin/acacia co mplex coacervates optimized for maximum coacervate yield were compared . The albumin/acacia coacervate was shown to be three orders of magnit ude more viscous than the gelatin/acacia system,