The most complex emulsions are those of foods and, therefore, are difficult to stabilize. An infinite number of microstructures of combinations of proteins, carbohydrates, fats and lipids are present in food systems. There is an increasing awareness of many investigators to the relevance of the principles of colloid and surface science to many of the technological problems related to advanced foods. Amphiphilic molecules play a key role in the stabilization of many of the food colloids. It is, therefore, very important to understand the interfacial behaviour of these molecules and to select the proper ones for the proper activity. Synthetic surfactants and emulsifiers are widely used in many of our foods, but, it becomes very important to replace them by natural molecules with good health records. The following review discusses the main natural ocurring molecules that are in use today and the future trends in this area. Monomeric emulsifiers such as mono and mono-diglycerides, lecithins and lysolecithins are still key players. Glycolipids are present only in very minor concentrations in plants and animals and therefore are not commercially available. Saponins are a very interesting group of materials with increasing potential. The polymeric amphiphilic compounds are "native" and enzymatically modified proteins. However, in situ products chemically modified by a Maillard reaction can also be used as emulsifiers. The most interesting new emulsifiers are some selected hydrocolloids that exhibit surface properties and emulsification capabilities. Enzymatically modified hydrocolloids show significant promise. Biosurfactants have also been studied and considered as emulsifiers, but are not food grade products. New trends and progress will also be discussed. (C) 1999 Elsevier Science B.V. All rights reserved.
