4.2 Lipids
Another important chemical class for food metabolites is lipids, which directly affect food texture, flavor, nutrition, and caloric density. As shown in Fig. 3-I, the spatial localization of lipids and other nutrients was mapped with MALDI imaging in Oryza sativa rice grains. Lysophosphatidylcholines (LPCs) were localized in the endosperm, but various phosphatidylcholines (PCs) were mainly localized in the bran (germ and seed coat) (Yoshimura, Zaima, Moriyama, & Kawamura, 2012). MALDI imaging of Camelina seed sections revealed heterogeneous distributions of membrane lipid PCs and storage lipids (triacylglycerols), which hold precursor–product relationships. When compared with the acyl lipid distributions between wild type and transgenic lines, which are made to produce more oxidatively stable lipids, the MSI results provided new insights into the compartmentalization of oilseed lipid metabolism. The heterogeneous distribution of acyl lipids in Camelina embryos suggests that tissue-specific metabolite distributions may or may not be changed effectively in transgenic seeds, an outcome that depends heavily upon the targeted enzymes or pathways (Horn et al., 2013).