Gelation dynamics and rheological properties of stirred yogurt alternatives manufactured from pulse protein isolates and their hydrolysates

This study investigated the impact of enzymatic proteolysis of pulse proteins on the gelation dynamics, rheological, and tribology properties of plant-based yogurt alternatives (PBYA). Pea (PPI) and lentil (LPI) protein isolates were partially hydrolyzed to ∼1 % degree of hydrolysis. Both protein isolates (PPI and LPI) and their respective hydrolysates (PPH and LPH) were used to manufacture PBYA via fermentation. The fermentation-induced gelation took nearly 5 h to reach pH 4.3 as the target pH. The gel hardness of PPH- and LPH-PBYA gels was reduced compared to PPI- and LPI-PBYA. Hydrophobic interactions dominated in stabilizing the PBYA gel structure, irrespective of the hydrolysis treatment. In contrast, partial hydrolysis increased other intermolecular interactions in PPH- and LPH-PBYA, e.g., electrostatic, hydrogen bonding, and disulfide interactions. Despite such an increase, stirred PPH- and LPH-PBYA exhibited reduced gel particle size and increased syneresis rate. These phenomena may be attributed to the production of smaller-sized polypeptides during hydrolysis. Consequently, an increase in the overall population of reactive components for protein-protein interactions may be expected; this resulted in a more compacted structure of protein aggregates or network, but not necessarily strengthening the gel structure, which is mediated by hydrophobic interactions. PBYA made from hydrolysates (PPH or LPH) showed higher frequency dependence regarding rheological properties tested in LAOS regimes. These findings may direct new product development activities for improving PBYA texture with smoother and softer textural attributes. Future research efforts are recommended to explore approaches for improving PBYA gel phase stability.