Thirty-three samples of proso millet ( Panicum miliaceum) with different countries of origin were screened for their pepsin digestibility after cooking to identify samples with high digestibility. The pepsin digestibility of all samples ranged from 26% to 57% (average 32%). There were no apparent differences in protein profiles (by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, SDS-PAGE) of samples with the lowest, intermediate, and highest digestibilities. However, liquid chromatographic-tandem mass spectrometric (LC-MS/MS) analysis revealed a negative correlation between pepsin digestibility and peptides that matched to high molecular weight proteins (24 kDa) from Panicum hallii with regions of contiguous hydrophobic amino acids. Low digestibility upon cooking was also observed for other species from the Panicum genus, such as little millet, switchgrass, and panicgrass, which suggests a unique inherent property of the genus. The results obtained from this study may form a basis for in-depth analysis of proso proteins that may help in developing new cultivars with higher digestibility upon cooking.
Keywords: accessions; gluten-free; panicins; protein identification; switchgrass.