UBC Theses and Dissertations
Formation and characterization of legume protein amyloid fibrils Zamani, Sara
Amyloid fibrils are gaining attention as novel food ingredients and nanomaterials, due to their unique structural and chemical properties, and functionality as stabilizers and gelling agents. Amyloid fibrils are long, thin, unbranched protein aggregates that are important in medicine, biology and nanotechnology. Many proteins, including food proteins (e.g., from milk, eggs, and legumes), can be converted into amyloid fibrils under the proper conditions, most commonly by heating at low pH. Most of the research on nanofibrils has dealt with animal proteins, so a fundamental understanding of the self-assembly, structure, and functionality of nanofibrils derived from plant proteins is lacking. Plant protein is considered a sustainable source of protein. However, the functional properties of plant proteins, such as foaming, gelling, and emulsification, are generally inferior to that of animal proteins. Consequently, one method to improve the functionality of plant proteins is to produce nanofibrils, which are promising materials. The goal of this research was to relate nanofibril structure and functionality by comparing nanofibrils made from various legume proteins. Nanofibrils were formed from peanut, lentil, pea, and mung bean during incubation at pH 2 and 85 °C. The results showed that protein extracts from peanut, mung bean, pea, and lentil formed nanofibrils, which were detected using thioflavin T and transmission electron microscopy (TEM). SDS-PAGE revealed that extensive protein hydrolysis occurred during the onset of fibril formation, indicating the significance of hydrolysis to fibrillation under these conditions. Using TEM, fibrils from different legumes showed morphological variability with differences in length, width, and flexibility. This research revealed that peanut, lentil, and mung bean fibrils were most soluble at pH 2 and least soluble at isoelectric point (pI) pH. Also, the fibrils showed smaller particle size at pH 2 to that of pH 7 which is consistent with the solubility result. The presence of the fibrils results in an increase in viscosity compared to the unheated samples. The findings showed that a better understanding of legume fibrils is needed to increase their usage as functional materials in food systems, and that this would probably extend theoretical knowledge of the structure-function relationship between plant-based fibrils.
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