UBC Theses and Dissertations
Characterizing the assembly kinetics, seeding, and gelation of lentil protein nanofibrils Shi, Lanfang
Food protein nanofibrils may have improved functionalities in food applications owing to their highly ordered structures and extreme aspect ratios. Protein fibrillization is typically inducible at high temperature and low pH, where proteins are hydrolyzed and self-assemble into fibrils spontaneously. This process may be accelerated by seeding with fragments of pre-formed fibrils. As plant proteins are becoming more prevalent as environmentally sustainable and healthy alternatives to animal proteins, more research has begun to focus on legume protein fibrillization. Lentils are a major Canadian pulse crop with high protein content, but little is known about lentil protein fibrillization. The objectives of this project were to evaluate (1) the effects of protein extraction conditions (acidic vs. alkaline pH), (2) seeding with pre-formed fibrils on lentil protein fibrillization, and (3) the gelation of lentil protein fibrils. Lentil proteins extracted at either pH 8.2 or pH 3.5 with salt were incubated at 80 °C, pH 2, with stirring, to form fibrils. The protein composition and hydrolysis pattern during fibrillization and the fibrillization kinetics of the two protein extracts were found to be similar. However, transmission electron microscopy revealed apparent morphological differences—fibrils made from alkaline extract were more heterogeneous, curly, and tangled, whereas fibrils made from acidic extract were more uniform, long, and straight. Further analyses with UV-vis spectroscopy, the Fast Blue BB assay, and LC-MS indicated the presence of protein-phenolic interactions in the alkaline extract, which likely affected fibrillization. The acidic extracts were used for further studies of fibrillization. The lag time, growth rate, conversion yield, and fibril morphology were evaluated for seeded and unseeded fibrillization. Seeding with 3% w/w seeds significantly decreased the lag time (p<0.05). The evaluation of thermal gelation at pH 2 showed that crude lentil fibrils were able to form strong, colorless, and translucent gels. However, phase separation was observed in ion-induced cold gelation at pH 8, likely due to the structural fragmentation of fibrils during pH neutralization. This project expands our fundamental understanding of lentil protein nanofibrils, from the assembly kinetics to gelation properties, which opens more possibilities for their future use as novel plant-based ingredients.
Item Citations and Data
Attribution-NonCommercial-NoDerivatives 4.0 International