Plant-based sources are under increasing demand to provide new protein ingredients. Lupin seeds with an average protein content of 35-44% are an emerging source of alternative protein. Lupin fortified foods have many health-promoting benefits such as lowering cholesterol and blood pressure, managing glucose levels and helping to fight obesity by lowering energy intake while increasing satiety. The sweet lupin varieties such as narrow-leafed lupin (Lupinus angustifolius, blue lupin, or NLL) are increasingly popular pulse crops, because of their nutritional and nutraceutical properties in addition to their lower content of anti-nutritional alkaloids.
In this study, the major lupin seed proteins, referred to as conglutins, were identified in the mature seeds of NLL commercial cultivars Tanjil and Unicrop and the wild accession P27255. The influence of protein extraction buffer composition on the number of identified conglutin proteins and the abundance of measured marker peptides attributed to these proteins were evaluated. In addition, the reproducibility of extraction protocols was assessed, to develop and optimise an efficient extraction protocol for identification and quantitation of conglutin seed storage proteins.
Discovery proteomics analysis was performed on a TripleTOF 6600 (SCIEX) mass spectrometer and the conglutin expression profiles across these three NLL cultivars were studied through quantitative multiple reaction monitoring workflow undertaken on a QTRAP 6500+ (SCIEX) system. The Tris buffer resulted in the lowest number of proteins identified across all the cultivars and yielded lower levels of gamma conglutins. The comparative study of conglutins within the selected cultivars, revealed different expression levels in some beta conglutins which are known as putative allergens.