Objective: Digestibility is a concern for pigeon pea and other legumes proteins, due to co-existing compounds in the seed matrix hindering protein accessibility. Germination was used to investigate the digestibility of the underutilized pigeon pea proteins. Methods Used: Pigeon pea seeds (10 g) were washed and sterilised with 70% ethanol and distilled water, placed in a petri dish and incubated at 25°C for 48 h. Control samples were collected prior to incubation (0-h), with other sampling points at - h (pre-germination), 24-h (at germination) and 48-h (post-germination). Seeds were cut across and used for scanning electronic microscope imaging (SEM). Samples were freeze-dried and pulverised; prior to alkaline solubilization and acid precipitation protein extraction. Lowry assay and SDS-PAGE were used to determine the protein contents and profile of the protein isolates. Pulverised samples from each sampling point were subjected to in vitro gastrointestinal digestion and the degree of hydrolysis (DH) was quantified by ortho-phthalaldehyde method. Digested and non-digested 0-h and 48-h samples were used for amino acid composition and PDCAAS analyses. FTIR was used for proteins secondary structure analyses of 0-h and 48-h samples.
Results: Germination altered the seed microstructure, increased the α-helix content (5%), DH (15.6%), PDCAAS (25%), total amino acids (19.4%), sulphur-rich (62.8%) and essential amino acids (18.2%) contents; nonetheless, extractable protein isolate yield (13.5%) and the β-sheets (4%) decreased.
Conclusions: Germination increased the total amino acids content, protein quality and digestibility, therefore, could be used to enhance pigeon peas nutritional qualities towards improving the utilization of these proteins.