Mass spectrometry imaging of diacyl-, alkylacyl-, and plasmalogen-phosphatidylethanolamines in pork chop tissues

Phosphatidylethanolamine (PE) is a major phospholipid in pork and a determinant of its quality. PE is classified into diacyl, alkylacyl, and plasmalogen types. Plasmalogens have antioxidant activity and are believed to have beneficial health properties. However, their presence in pork tissues have not been fully elucidated. Here, we analyzed their distribution in longissimus thoracic et lumborum (loin) muscle, spinalis muscle, intermuscular fat, and transparent tissue of pork chops. Liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) revealed 14 diacyl-PEs, 10 alkylacyl-PEs, and 24 plasmalogen-PEs, suggesting that plasmalogen-PEs are a dominant type, and a major reservoir of eicosapentaenoic and docosahexaenoic acids. Matrix-assisted laser desorption/ionization-mass spectrometry imaging (MALDI-MSI) revealed that the distributions of PEs among tissues depended on fatty acid compositions at sn-1 and sn-2 positions. Interestingly, diacylPEs were most abundant in intermuscular fat tissue; whereas alkylacyl-PEs and plasmalogen-PEs were highest in transparent tissue. To the best of our knowledge, this is the first report showing tissue-specific distributions of the three types of PEs in meat using MALDI-MSI. These results suggest that MALDI-MSI with LC-ESI-MS is a useful tool for distribution analysis of the three types of PEs in pork tissues. [GRAPHICS] .