Interactions between proteins and hydrocolloids during human digestion of emulsions.

C Fernández Fraguas, NC Woodward and PJ Wilde 

Institute of Food Research, Norwich Research Park, Norwich, NR4 7UA, UK. 

Obesity is a major health problem in the developed world and a risk factor for chronic diseases (diabetes and cardiovascular disease). Lipids are the most energy dense of macronutrients and excess consumption has been linked to obesity. By slowing down lipid digestion is thought that we can induce feelings of satiety and reduce subsequent food intake by reducing appetite. 
Changes in food manufacturing are needed to develop healthier products and ingredients. Most emulsified foods, particularly those containing reduced fat, contain viscosity modifiers to enhance texture and consumer acceptability. Emulsion production involves the creation and stabilisation of an interface, between the liquid fat and water, covered with emulsifiers or proteins in order to stabilise them against coalescence and separation. The breakdown of lipids from processed emulsions in the digestive tract will depend on the accessibility of lipases to the fat/water interface, so the composition at the fat interface can affect lipid digestion in vitro. 
Previous studies have facilitated an understanding of how the properties of the interface might influence the digestion process in model systems but, since we eat complex food products, it is also necessary to understand how ingredients such as gels and thickeners can be used to modify lipid digestion, either by slowing it down to promote satiety, or to enhance release and uptake of valuable lipid-soluble ingredients. Therefore, this research work describes studies aimed at determining how common food structures found in emulsified foods can influence the breakdown and digestion of lipids in vitro. The interaction of these structures with digestive enzymes, surfactants and lipids has been studied under simulated gastro-intestinal conditions.
The progress made in understanding the role of hydrocolloids during structure formation of model food systems will provide the opportunity to create novel structures, between proteins and different polysaccharides which will have a varied response to the conditions they are exposed to during the digestion process. The knowledge gained from this research could be useful to explain the digestion of commercial food emulsions and to develop intelligent strategies to modify or design new products to optimise fat digestion.