Behaviour of formula emulsions containing hydrolysed whey protein and various lecithins.

Formula emulsion systems are used as enteral, sports and health products. In some formulas addition of hydrolysed protein is necessary to guarantee ease of digestion and hypoallergenicity. In the low fat emulsion model an increase in the content of lecithin (phospholipid mixture) was required, in consideration of the advice of the Food and Nutrition Board (USA) for choline supplementation. The individual and interactive effects of whey protein isolate (WPI) or hydrolysate (WPH) (3.7 and 4.9% w/w), unmodified deoiled or hydrolysed lecithin (0.48 or 0.7% w/w) and carbohydrate in the form of maltodextrin with dextrose equivalent (DE) 18.5 or glucose syrup with DE 34 (11% w/w) on the properties of formula emulsions with 4% v/w sunflower oil, were investigated using a full factorial design. The emulsions were characterised by particle size distribution, coalescence stability, creaming rate, and also surface protein and lecithin concentration. WPI-containing emulsions proved to be stable against coalescence and showed only little creaming after 1 and 7 days standing. There was a significant increase in the mean droplet size and a significant deterioration of coalescence and creaming stability when WPH instead of WPI was used as the protein source, due to the lower number of large peptides and lower surface activity of the WPH. Increasing the WPH concentration led to an increase in oil droplet size and further deterioration of the stability of the emulsions. The starch hydrolysate and lecithin also significantly influenced the emulsion properties. Their influence was less strong when the emulsion contained WPI. Under the conditions used WPH-based emulsions were more stable, in terms of creaming and coalescence, when a low level of protein was used in conjunction with hydrolysed lecithin and glucose syrup. Oil droplets in emulsions containing unmodified lecithin in either the continuous or disperse phase and WPH in the continuous phase were very sensitive to coalescence. The addition of starch hydrolysates (DE 18.5) induced intensive flocculation and phase separation in these emulsions.