Study of the gelation of milk by Diffusing wave spectroscopy (DWS) (CAT#: STEM-MB-0838-WXH)

Introduction

Milk, as a convenient colloidal suspension of considerable significance to the food industry, has been by far the most studied material in DWS experiments. Skimmed milk consists of polydisperse protein particles (the casein micelles), with radii in the range approximately 40–150 nm, dispersed in aqueous serum. The particles themselves are association colloids and are protected by a surface layer of one of the caseins, κ-casein. The κ-casein possesses an extended chain (caseinomacropeptide) that protrudes from the micellar surface and provides steric stabilization to the particles. This “hairy layer” can be removed specifically by the action of a proteolytic enzyme (chymosin), and this so called renneting reaction destabilizes the casein micelles and allows them to form a coagulum. A n alternative destabilization of the micelles is by progressive acidification, during which the surface layer is collapsed, and then the particles coagulate