Understanding the determinants of pea protein functional quality: impact of protein composition, protein denaturation and non-protein components

Plant proteins have received a lot of attention in the last decade for environmental, economical and societal reasons. Many researches have been performed to extract proteins from plant sources, which have demonstrated strong differences in terms of functionality between plant proteins from different sources and obtained with different extraction processes. However, most of these studies are descriptive and the reasons for these differences are not fully understood.

The objective of this study was to gain better understanding of the determinants for plant protein functional quality, investigating the impacts of protein composition (albumin, legumin, vicilin), non protein material (sugars, pea starch), and level of protein denaturation. To do so, pea proteins were fractionated at the pilot scale and their functional properties were evaluated individually. Pea starch and pea sugars were also purified, collected and added to pea proteins to evaluate their effects. The different components were then recombined to generate the equivalents of air-classified pea protein concentrate, pea protein isolate obtained by isoelectric precipitation and pea protein isolate obtained by membrane filtration, and compare them to real products.

Contrasted functional properties were observed for albumins, legumins and vicilins; albumins tend to have very strong foaming, gelling and emulsifying properties; vicilin have better foaming properties than legumins, while legumins have better emulsifying and gelling. Protein denaturation enhanced emulsifying properties, possibly due to increase of hydrophobicity, but reduced gelling. Non-protein material also impacted ingredient functionality, positively or negatively. Interactions were found between individual proteins and between protein and non-protein components.

These findings may be useful for cultivar selection and in process development, by better adjustment of protein composition and elimination / recovery of components depending on the functionality targeted.