The valuable health-promoting benefits and technological characteristics of lupin have led to its growing use as an ingredient in a broad range of food products. However, as a result of growing consumption of this valuable legume in the food industry, the number of allergic reactions to lupin proteins has reportedly increased, with noted cross-reactivity to other legumes, particularly peanut. To protect public health and safety of the allergic individuals, lupin declaration on the ingredient list has become mandatory in many countries including Australia, hence, it is crucial to design reliable methods for accurate detection of lupin proteins in food products.
In this study the proteins of lupin flakes produced from Australian narrow-leaved lupin (NLL) (Lupinus angustifolius) have been identified through a sensitive bottom-up proteomics approach and bioinformatic analysis. The proteome of NLL resulted from using three different extraction buffer composition were identified and compared. In addition, the effects of the pre-extraction defatting step on the number of identified proteins were investigated. Discovery proteomics was performed on a TripleTOF 6600 (SCIEX) mass spectrometer which was followed by the identification of peptides and proteins using ProteinPilot software employing a genome-derived protein database.
The highest number of protein identifications was achieved using a urea-based extraction method which led to characterisation of many seed storage globulin proteins (conglutins) that exhibited high sequence similarity to known reference food allergens of NLL. A pre-extraction defatting step did not significantly increase the protein identifications.
The choice of sample preparation method influences the composition of the mass spectrometry-derived lupin proteome.