Preparation of high protein micro-particles using two-step emulsification

Abstract

We have developed a robust procedure for preparing protein micro-particles with a high internal protein content (∼20% w/w). Such protein micro-particles, having controlled size, protein content, and surface composition can be useful in the development of novel food products with high protein content. Protein particles were formed through emulsification of a WPI (whey protein isolate) solution (25% w/w) in sunflower oil containing 2.5% (w/w) PGPR (Polyglycerol Polyricinoleate) as an oil-soluble emulsifier. The emulsion (w/o) was heated to induce gelation of the protein inside the emulsion droplets. Oil was removed through successive centrifugation and washing steps. This resulted in micron-sized protein particles dispersed in an aqueous phase. The average diameter of the particles was in the order of a few μm, depending on the mixing speeds applied in the primary emulsification step. CLSM (Confocal laser scanning microscopy) analysis of protein particles indicated that there is oil associated with the particles, either surrounding the particles and/or distributed throughout the particles. NMR analysis showed that this amount of oil does not exceed 1.8% (w/w).