64-8 |
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H. SINGH, A. Ye, and Y. Hemar. Riddet Centre, Massey University, Private Bag 11222, Palmerston North, New Zealand Hydrolysed milk proteins are extensively used in infant and specialized adult nutritional formulations. Because of the poor emulsifying properties of hydrolysed proteins, these formulations usually require the addition of emulsifiers and stabilizers to facilitate the formation of stable emulsions. Polysaccharides are commonly used to stabilise food emulsions, but the mechanisms involved are not well understood. Our objective was to further our understanding of how xanthan influences the formation and properties of emulsions formed with highly hydrolysed whey proteins under a range of conditions. Emulsions were prepared by homogenization of mixtures of corn oil and aqueous solutions containing a highly hydrolysed whey protein product, lecithin and xanthan gum. The emulsions were characterised using particle size analysis, viscosity measurements and confocal laser microscopy. Stable oil-in-water emulsions could be formed using 4 wt% hydrolysed whey protein product and hydroxylated lecithin as emulsifiers. Addition of xanthan to these emulsions above a certain critical concentration caused flocculation of the oil droplets, by depletion mechanisms, which resulted in a marked increase in the creaming rate. Interestingly, this depletion flocculation also promoted the coalescence of droplets during storage of the emulsions for up to 1 week at room temperature. The rate of coalescence was enhanced considerably with increasing concentration of xanthan in the emulsion up to 0.12%. At higher levels of xanthan addition, the rate of coalescence decreased gradually, apparently because of the high viscosity of the aqueous phase. These findings are very useful in understanding how varying the level of a polysaccharide in a food emulsion can change its destabilizing/stabilizing properties. The work shows for the first time that the coalescence of droplets is accelerated in the presence of xanthan. The importance of integrity of interfacial adsorbed layers in the stability of emulsions is highlighted.
Session 64, Dairy Foods: Milk proteins
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