Nutritious, high in protein and low in allergens. Pea protein is currently trending among bodybuilders and health junkies.

This plant-based product is commonly purchased in powder form and mixed with water or milk to make a protein shake. But it can also be added to smoothies, oatmeal and many other foods. Despite its health benefits, however, its incorporation into commercial foods has been limited. This is primarily because pea proteins traditionally have low solubility, meaning pea protein shakes have a chalky texture – which may turn off consumers and limit the products’ appeal.

Seeing the potential of pea protein, a research team from NUS Food Science and Technology has proposed a two-step process to make pea protein a viable ingredient: sodium carbonate (Na₂CO₃) treatment, followed by acidification. Published in Food Hydrocolloids, the study found that this method boosted pea proteins’ solubility, foaming, and emulsifying performances, within both neutral and acidic environments.

From protein content to shelf life, pea proteins’ functional properties have a big impact on the quality and reliability of its commercial products. Moreover, thermal treatments during manufacturing, which are necessary for food safety, can cause proteins to unfold and clump together, further lowering their water-related functionalities.

Food scientists have employed strategies ranging from chemical treatments to high temperature processing to improve the situation. However, these strategies often run into challenges related to their implementation, food safety, quality control or consumer resistance to additives.

Greener, safer, more desirable

In contrast, the team’s proposed treatment is a simple, environmentally friendly process which only uses food-grade materials. “No harsh chemicals were used,” said Professor Zhou Weibiao, the study's lead author.

The first step, sodium carbonate treatment, disrupts the pea protein’s structure, leading to smaller, more flexible, surface-charged particles, with newly exposed hydrophobic (water-repelling) patches. This gives the proteins a well-balanced equilibrium of hydrophilic (water-attracting) and hydrophobic areas for better foaming and emulsification, plus enough surface charge to repel other particles and stay dispersed in water.

Most beverages on the market, however, are acidic, noted the researchers. While effective, sodium carbonate is alkaline. Thus, a second step, acidification, is needed to produce a more commercially desirable acidic pea protein suspension. This step refolds the protein but partially retains the improved functional properties achieved under the alkaline step.

The researchers investigated the effectiveness of the two-step treatment within a pH range of seven to three by comparing the experimental group with a control that had only undergone hydrochloric acid (HCl) acidification.

While hydrochloric acid is widely used in the food industry as a processing aid for pH adjustment, it is nevertheless a strong inorganic acid – giving it a negative consumer image. Hence, the researchers added a parallel experimental group, replacing hydrochloric acid with citric acid, a mild organic acid found naturally in fruits, to align their research with growing consumer demand for clean label ingredients.

The proposed two-step treatment showed robust improvements in pea protein’s functional properties. Some topline results include a 35 percent jump in solubility and a 13 percent increase in foam volume.

More pea protein products

Improving pea proteins’ functional properties raises the potential of new pea protein markets, said first author He Chengxin. Better foaming properties, for example, can encourage the sale of pea-protein-based cakes and other products.

Plus, the researchers found that between hydrochloric acid and citric acid, the better performer for acidification was dependent on the desired pH level. The study’s findings can therefore help inform food manufacturers on which acid should be used in their production process, depending on the target pH of their final product, Zhou explained. At weakly acidic conditions typical of most beverages, for example, citric acid is the better choice.

High-protein products can also help meet growing nutritional demands. With higher solubility, consumers may have access to a wider range of sustainable protein-rich products, and if pea protein shakes are the beverage of choice, enjoy them with a smoother, more satisfying texture.