Protein digestibility and techno-functional performance of milk-alternative prototypes based on combinations of lentil and cereal protein†

Abstract

Lentil protein isolate was combined with proteins from oat, rice, brewer's spent grain (BSGP) and wheat to achieve plant-based milk alternatives (PBMA) with improved protein quality and functionality. Due to the complementary amino acid (AA) profile of pulse protein which is high in lysine, and cereal protein which is high in sulphur amino acids, their combination at an optimised ratio resulted in a protein blend with a significantly improved indispensable amino acid score (IAAS) compared to the single ingredients. All protein combinations with lentil except for wheat resulted in a full IAAS for adults. The in vitro protein digestibility was assessed using the static INFOGEST digestion model to calculate the proxy in vitro DIAAS (PIVDIAAS) of the emulsions. Techno-functional properties such as particle size, rheological behaviour and physical stability were investigated. The PIVDIAAS of the combined protein emulsions was found to be 0.72, 0.78, 0.83, 0.98 for lentil + wheat, lentil + oat, lentil + BSGP and lentil + rice emulsions, respectively, compared to 0.48, 0.25, 0.5, 0.67 and 0.81 determined for the emulsions based on lentil, wheat, oat, BSGP and rice alone, respectively. The emulsions based on the combination of lentil and cereal protein also showed improved physical stability regarding sedimentation and creaming, and a higher whiteness index of the emulsions. It could be shown that the combination of lentil and cereal protein is a promising strategy to achieve PBMAs with improved protein quality and techno-functionality.