Electrospray mass spectrometry as a tool to characterize phospholipid composition of plant cakes

Phospholipids (PL) are components of increased value in nutritional applications, especially those rich in polyunsaturated fatty acids (PUFA) such as -linolenic acid (ALA, 18:3 n-3) and linoleic acid (LA, 18:2 n-6). Currently, the oil processing industry generates by-products in the form of oilseed and plant cakes that can be valorized for food/feed applications. With the aim of diversifying PL sources and improving their identification in terms of fatty acid (FA) composition, plant cakes obtained from five different sources (camelina, flaxseed, hemp, sesame, walnut) were extracted and analyzed by lipidomics approach using three analytical methods of mass spectrometry (MS): (i) shotgun; (ii) reverse phase liquid chromatography (RPLC) in multiple reaction monitoring (MRM) mode; and (iii) normal phase liquid chromatography (NPLC) with data dependant scan MS fragmentation. We obtained complementary information: while shotgun allowed identifying PL species, RPLC associated to MRM enabled to access high sensitivity and to focus on minority species. Then, NPLC in data dependant scan led to the identification of lysophospholipids and cardiolipin species besides phosphatidylcholine (PC). Among, the five plant cakes analyzed, camelina cake showed the highest percentage of ALA. If ALA was also found in flaxseed and hemp cakes, it was in a lesser extent. Moreover, ALA was located on the sn-2 position of the glycerol backbone, a valuable position for nutritional applications. Practical applications: The food industry generates large amounts of by-products, and most of them remain unused. Among them, degumming pastes, i.e., by-products from the oil refining process, could be valuable sources of phospholipids (PL). These phospholipids present interesting properties, as emulsifiers, thickening agents, or antioxidants, for food or cosmetic industries. Moreover, depending on the plant source, the fatty acid composition in phospholipids could be different from that of the oil (mainly composed of triglycerides instead of phospholipids), especially for -linolenic acid (ALA, 18:3 n-3). Among, the five plant cakes analyzed (camelina, flaxseed, hemp, sesame, walnut), camelina cake showed the highest percentage of ALA. If ALA was also found in flaxseed and hemp cakes, it was in a lesser extent. Moreover, ALA was located in the sn-2 position of the glycerol, a valuable position for nutritional applications. On the whole, using powerful and complementary analytical procedures for PL characterization allowed widening the potential sources of this type of lipids. Workflow of the plant cake lipid analysis based on three analytical methods of mass spectrometry