Guidelines for Processing Emulsion-Based Foods

Abstract

Emulsions are dispersions of one liquid into the second immiscible liquid in the form of fine droplets. Emulsions can be classified as either oil-in-water or water-in-oil emulsions depending on whether oil or water is the dispersed phase. Milk, cream and sauces are some examples of oil-in-water emulsions whereas butter and margarine are examples of water-in-oil emulsions. This chapter discusses the physical principles that are involved in the formation and stability of food emulsions. Prediction of droplet size distribution for food emulsions that are formed in colloid mill (predominantly by shear) and high pressure homogenizer (predominantly by turbulence) in terms of operating conditions in these equipments is discussed. The fluid mechanics of droplet breakage and coalescence in shear and turbulence are discussed and applied to the formation of food emulsions and to the prediction of drop size. The role of proteins and surfactants on the stability of emulsions is discussed. The effect of interfacial dilatational and shear elasticity on thin film stability and drop coalescence is described. Some recent results of a new technique, layer by layer deposition, to improve the shelf life of emulsions by using alternate layers of proteins and polysaccharides is presented. Thermodynamics and phase behavior of microemulsions and its application to food is discussed.