Preparative chromatography for purification of 7S globulin from pigeon pea seeds to improve foaming properties

International audience

English. Pigeon pea is a protein-rich pulse (18-28 wt. %) native to emerging countries in Asia and Africa. Globulins comprise the largest portion of pigeon pea proteins (around 60%), with the 7S fraction being the most abundant. Understanding the interplay between the physicochemical and the functional properties of individual globulins of pulse protein ingredients is of great importance for optimizing their performance in food systems. Protein purification makes it possible to isolate individual protein fractions from total extracts and investigate their role in the functionality of protein ingredients.In this work, pigeon pea 7S globulin was purified on a preparative scale using ion exchange chromatography followed by size exclusion chromatography. The purified fraction presented a protein content of 89 g/100 g powder and a yield of around 23%. A combination of different techniques, such as polyacrylamide gel electrophoresis in sodium dodecylsulfate (SDS-PAGE), size exclusion high performance liquid chromatography (SE-HPLC), proteomic analysis and fluorescence spectroscopy allowed to characterise extensively the purified fraction composed of two main subunits of 64 and 49 kDa, identified as the α- and β-chains of β-conglycinin. The 7S globulin had better foam stabilisation properties compared to the crude protein extract from pigeon pea seed, whey proteins and bovine serum albumin. Therefore, the developed purification protocol showed to be suitable for purifying pigeon pea 7S globulin in sufficient quantities for characterization and evaluation of the functional properties. The latter, in turn, highlight the potential of this protein fraction for applications as a foaming agent in the food industry, as an alternative to animal proteins.