Pro Tip: Soy protein isolate combined with an emulsifier, such as glycerol monostearate (GMS) or lecithin, shows promise as an egg replacer.

The egg replacement market is growing quickly in the United States, driven by a combination of changing consumer preferences and the recent increase of the price of eggs. However, replacing the foaming, emulsifying and gelling functionality imparted by the proteins and phospholipids in egg whites and yolks is challenging.

A variety of ingredient blends comprised of plant-based protein, hydrocolloids (like xanthan gum) and emulsifiers can help, but many still lack in their functionality, especially in terms of cake.

One combination that shows promise is soy protein isolate combined with an emulsifier, such as glycerol monostearate (GMS) or lecithin. In some cases, these are sold as blends (i.e., lecithinated soy flour/protein), although these ingredients can also be combined at the mixer when producing cake batters.

This ingredient combination works by taking advantage of soy protein’s structure to form a gel during baking, while a combination of the soy protein and the added emulsifiers work together to control the viscosity of the batter, leading to stable products during processing.

Cake texture is partly defined by the strength of crumb structure, made from a combination of protein and starch. A dense crumb structure can lead to chewy undesirable products; this is often what happens if only soy protein is added to batter.

Crumb structure is significantly impacted by the viscosity and specific gravity of the batter during production.

The specific gravity is the ratio of the weight of a constant volume of batter to the same volume of water. In this way, it is an indicator of how much air is trapped inside the batter. If the specific gravity is low, this indicates that a lot of air has been incorporated into the batter, and it might collapse during baking if the air cells grow too big before the starch and protein solidify.

Conversely, if the specific gravity is too high, an insufficient amount of air has been incorporated, which can lead to a dense crumb structure.

When soy protein is added to cake batter, the viscosity increases since soy protein absorbs lots of water, which can extend shelf life.

However, this also leads to more air being incorporated into the batter. As the cake undergoes processing, the gas produced by the chemical leavening causes these air cells to grow too big and collapse.

If an emulsifier is added to the dough with soy protein, this viscosity is much less. This is because the emulsifier allows for smaller oil droplets in the batter, and it can help to better distribute the water and oil throughout the mixture, leading to cake batters with a better specific gravity.

When soy protein and the emulsifier are baked along with starch present in wheat flour, the amylopectin in starch unfolds, leading to gelatinization, while the soy protein forms a gel through disulfide bonds. All the while, the emulsifier helps to prevent the gas and oil cells from merging together (coalescing), leading to a better final crumb structure than either product alone.

While there is still some trial and error needed to optimize the levels of these ingredients, it has been found that total replacement of eggs with soy protein isolate is possible when lecithin or GMS are added to the batter, leading to cakes that are similar to egg-based cakes in textural and many sensorial properties.

However, the soy-based cakes were often slightly darker and chewier, problems that can be addressed with processing conditions like bake time and temperature, as well as the use of hydrocolloids that can lead to softer final products.

Harrison Helmick is a PhD candidate at Purdue University. Connect on LinkedIn and see his other baking tips at

His research is conducted with the support of Jozef Kokini, Andrea Liceaga, and Arun Bhunia.