Pea protein globulins: Does their relative ratio matter?

Abstract

The relatively low abundance of 11S legumin in pea protein, coupled with the wide diversity in 7S vicilin to 11S legumin ratio among pea protein ingredients, are assumed contributors to inferior and inconsistent properties relative to soy protein. To improve the performance of pea protein ingredients in food applications, optimum protein profile must be identified. Therefore, this work followed a holistic approach to determine the impact of 7S/11S ratio on pea protein structure, functionality, and nutritional quality. Vicilin- and legumin-rich fractions were isolated and combined in different proportions to produce samples of varying 7S/11S ratios. For the first time, pea protein isolate was also enriched with 11S legumin to evaluate the impact of 11S abundance on functionality within an unfractionated protein matrix. The low abundance of 11S in pea protein did not seem to be the cause of inferior properties. In fact, 7S vicilin had 6-fold higher gel strength and 5-fold higher emulsification capacity, but significantly lower nutritional quality, than 11S legumin. Despite having significantly higher sulfur-containing amino acids, high protein polymerization in 11S legumin contributed to relatively low functionality. Further, fractionation induced unique changes to amino acid composition, resulting in significantly lower amino acid scores for isolated 7S vicilin and 11S legumin relative to pea protein isolate. Accordingly, 11S legumin enrichment of pea protein isolate did not improve functionality or nutritional quality. Nevertheless, this work contributed foundational knowledge that will provide direction for future studies aiming at devising strategies to improve the quality and consistency of pea protein ingredients.