SummaryIn the present work high methoxylic, low methoxylic and amidated pectins were tested for their actions in whey protein emulsions using a broad variation in the emulsion composition (content of protein, pectin, oil) and the solvent conditions (pH, ionic strength). Emulsifying activity index, long term stability and the particle size of the emulsions were determined, protein and galacturonan content of the semm were analysed after centnfugation. A strong relationship was found between emulsion stability and degree of esterification of the pectin, the influence of pectin amidation was relatively low. There were formed stable electrostatic complexes between the protein and the carboxylic groups of the pectin. They seemed to be much more important for emulsion stability than the hydrophobic or hydrogen bonds. The emulsion properties varied in dependence on the content of the single emulsion components and on the solution conditions. All pectins used stabilized the whey protein emulsions if their concentration was high enough. For any individual utilization it is necessary to choose the best suitable pectin.
lntrod uctionProteins and polysaccharides play an important role in emulsification and emulsion stabilization. Proteins are important as emulsifiers and also as emulsion droplets stabilizers, while high molecular weight polysaccharides such as pectin act as gelling and thickening agents, changing the rheological properties of the continuous aqueous phase and so retarding or inhibiting emulsion destabilization [ 11.Various proteins and hydrocolloids can be used for the preparation of emulsions. The combination of proteins and hydrocolloids may result in better products. In some cases solutions containing proteins and hydrocolloids were mixed and emulsified [2, 31. Other authors [4, 51 formed complexes between proteins and anionic polysaccharides by mixing the components under specific conditions and then tested their emulsifying properties. The strongest connection between proteins and polysaccharides was reached by forming conjugates using a chemical procedure [6-81 or via controlled dry heating and formation of covalent MAIL-LARD-type products [9-111. This conjugate formation was the synthetic form of the naturally occurring materials like gum arabic, containing protein as well as polysaccharide components in a strong connection with good emulsifying properties.The combination of proteins and hydrocolloids in many cases caused not only a simple addition of the specific properties of both components. Depending on external and internal factors a new quality of emulsion properties could be formed.In the present work, whey protein concentrate as protein and various pectins as polysaccharide component are applied. Whey protein concentrate with its main components globular a-lactalbumin and fi-lactoglobulin is often used in the production of food emulsions [12-151. Pectins are traditionally applied for gel-like products, but some of them were also found to have stabilizing [5, 16, 171 and even emulsifying [ 18, ...
