Tuning plant protein functionality: from extraction to application

Which plant proteins are suitable for mass production, in taste, functionality and profitability? This question is critical, as the world population is expected to grow above 9 billion people in 2050 and the demand for high nutritional foods and proteins will increase. Common issues with commercial plant proteins are their low solubility and off-taste. We studied these issues and created new opportunities with green pea proteins.

Understanding the behaviour of plant proteins & solving solubility issues

To find a profitable way of producing (extracting and drying) plant proteins, it is crucial to understand their behaviour. The problem with many commercial plant protein ingredients is that often they exhibit a low solubility. NIZO has studied -and solved- this issue in protein extraction from green peas (Pisum sativa).

Research on pea proteins

The protein extracts were dried by freeze drying and spray drying under different conditions (heat loads). Pea proteins were chosen based on two aspects:

1. Their good nutritional values (balanced amino acid composition, with high level of lysine residues)
2. Being lactose and gluten free as well as not being genetically modified.

Crucial in the development of the extraction process was the possibility for up-scaling to pilot and industrial scale. Based on NIZO expertise, the spray-drying conditions were optimized for the time-temperature conditions resulting in highly functional plant protein powder, both in terms of powder characteristics and solubility.

Pea protein isolates with a protein on dry matter content of over 90% were obtained. Differential scanning calorimetry (DSC) was used to determine the denaturation enthalpy of the different powders.

The results

• Stable functionalities. The ‘native’ state of the protein is preserved after spray-drying as can be seen from the enthalpy values, which are very similar to the one obtained after freeze-drying. The differences between the two spray dried (sd) samples are the in- and outlet temperatures used and, thereby, the heat load.
• Better solubility. The solubility of the protein powders (even after 6 months storage at ambient temperature) remained high (>90% of the total amount of proteins). The solubility was determined at room temperature in water without salt addition or pH adjustment. The higher solubility was also reflected in the higher technical functionality of the protein powder, such as foaming and emulsifying properties.
• Improved taste. The optimised extraction and drying process did not only affect the degree of denaturation and solubility of the pea protein powder, but also had a remarkable impact on the flavour/taste profile.

The NIZO pea protein isolate and the commercial pea isolate 1 are both high in the attributes Pea and Green. These are flavour attributes that are related to the smell of pea and green vegetables/grass. Compared to the commercial products, the NIZO pea extract is extremely low in the attributes Beany, Cardboard and Wet socks. These attributes are generally associated with product defects with respect to fat oxidation off-flavours (Cardboard) and heat induced deterioration of proteins (Wet socks). The mouthfeel attributes did not show large variations between the samples. Especially the attribute Astringent, which is related to the molecular properties of plant proteins, did not show a significant difference between the samples. The NIZO pea protein extract has a more fresh character than the commercial products and has almost no oxidation off flavours.

Do you wish to have more information? Please contact our expert Fred van de Velde.