Browsing by Subject "extraction of legume proteins"

Substitution of animal food products and non-biodegradable plastics is of interest for addressing climate change and pollution. Plant proteins are potential raw materials with low environmental impact which can be utilized for development of protein rich foods or biodegradable plastics. Grain legumes and especially lupins are rich in proteins that could be utilized. Protein fibril is a self-assembled non-random protein structure which has a large length to width ratio. The objective of this study was to demonstrate the concept of fibrillating proteins extracted from two lupin species (L. albus and L. angustifolius) and to characterize the formed fibrils. The proteins were extracted from dried and milled lupin seeds with alkaline followed by an isoelectric precipitation. The standard extraction procedure was combined with additional process steps such as dehulling, defatting, extraction with acidic extraction media and dialysis. The extracted protein isolates were hydrolyzed into peptides in different concentrations and assembled into fibrils by heating at pH 2.0 for 24, 48 or 72 h. The fibrillated samples were analyzed with a thioflavin T (ThT) assay to indicate the β-sheet secondary protein structure. Some of the fibrillated samples were imaged with atomic-force microscopy. Samples prepared from dehulled and defatted L. angustifolius flour had the highest total protein content of 98.3 ± 0.4% on dry matter basis. ThT binding was observed in most samples indicating formation of fibrils. The binding increased significantly for samples after standard extraction process and for lower ionic strength. The fibrils appeared to form within 48 h and samples with higher protein concentration (40 mg/ml) showed massive gelation after 24 h. Studying the samples with atomic-force microscopy showed 300 nm long curly fibrils. These initial results indicate that the proteins extracted from lupin can be fibrillated.