Scientists from Iowa State University used a simple chemical modification technique to produce a soy protein which could also improve the foaming performance of egg white contaminated with yolk or other lipids.
“It is expected that such modified soy protein isolate can be used as an additive or ingredient in foaming formulation, especially when the egg white protein is suspected of lipid contamination,” wrote Guang Wang and Tong Wang in the Journal of Food Science.
Regarded as a premium ingredient with a high value-added perception from the consumer, eggs also hold a strong appeal for product formulators due to their wide range of functionalities, including coagulation, emulsification, foaming and crystallisation control.
However, soaring prices for grains such as soy and corn - that have seen feed costs leap by 30 per cent in twelve months - have hit egg prices particularly hard because the cost of feed is a large slice of overall costs when compared to other livestock such as beef cattle.
The new study, funded by the American Egg Board, investigated if chemical modification of a soy protein isolate (ADM) could subsequently improving foaming when added to both pure egg white and a yolk-contaminated egg white.
“The extent of yolk contamination may vary from 0.01 per cent to 0.2 per cent depending on specific operational conditions and raw material quality,” explained the researchers. “Even with 0.01 per cent contamination, egg white showed reduced foam expansion.”
The soy protein underwent an esterification reaction with methanol and hydrochloric acid. This modification was found to change the isoelectric point from 4.5 to about 10. The isoelectric point (pI) is the pH at which the egg protein has no electrical charge. The researchers used sonication, a technique whereby sound waves are used to irradiate the ingredient and speed up the reaction, and they found this was effective in redispersing the soy protein and improving the solubility profile.
When added to the egg white prior to foaming the modified protein “increased the foaming performance of both pure egg white and yolk-contaminated egg white”, wrote Wang and Wang.
Furthermore, when added to egg white contaminated with 0.4 per cent yolk, the researchers noted a full restoration of foam expansion and foam liquid stability, they said.
“It even out-performed the foaming of pure white protein,” wrote the researchers. .
Source: Journal of Food Science
Published online ahead of print, doi: 10.1111/j.1750-3841.2009.01306.x
“Improving Foaming Properties of Yolk-Contaminated Egg Albumen by Basic Soy Protein”
Authors: G. Wang, T. Wang