December 1/Ourimbah, Australia/Agriculture Week -- "The aim of this study was to evaluate the changes in Gelato vanilla ice cream physical properties such as viscosity, overrun and texture using different levels of sweet whey protein isolate (WPI) as substitutions for egg yolk. Gelato samples were made with two levels of egg yolk (4.5 and 9%)," investigators in Australia report.

"For each level, one control sample with no WPI addition and four levels of WPI substitutions (20, 50, 80 and 100%) was made. Three replications of each treatment were performed. Viscosity of the mixes was measured while Gelato ice creams were evaluated for overrun and texture (using Cone Penetrometer and Texture Analyser). Determinations of these parameters were made after four weeks of storage. The viscosity scores of the Gelato ice cream were influenced by fat content. Samples containing 9% egg yolk were more viscose than those containing 4.5%. Moreover, there was a significant increase (P<0.05) in overrun (%) by increasing WPI levels in both 4.5% and 9% egg yolk samples. However, higher overruns reduced ice crystal number, whereas lower overruns had no impact on size distributions," wrote M.S. Alfaifi and colleagues, University of Newcastle.

The researchers concluded, "In addition, WPI levels significantly influenced samples texture especially at 4.5% egg yolk, and increased samples hardness with increasing WPI."

Alfaifi and colleagues published their study in Milchwissenschaft -- Milk Science International ("Effect of Egg Yolk Substitution by Sweet Whey Protein Isolate on Physical Properties of Gelato Vanilla Ice Cream." Milchwissenschaft -- Milk Science International, 2010;65(4):404-407).

For additional information, contact M.S. Alfaifi, University of Newcastle, School Environmental & Life Science, Ourimbah, NSW 2258, Australia.

From the December 6, 2010, Prepared Foods E-dition