Unique Distribution of Diacyl-, Alkylacyl-, and Alkenylacyl-Phosphatidylcholine Species Visualized in Pork Chop Tissues by Matrix-Assisted Laser Desorption/Ionization-Mass Spectrometry Imaging

Phosphatidylcholine (PC) is the major phospholipid in meat and influences meat qualities, such as healthiness. PC is classified into three groups based on the bond at the sn-1 position: Diacyl, alkylacyl, and alkenylacyl. To investigate their composition and distribution in pork tissues, including longissimus thoracis et lumborum (loin) spinalis muscles, intermuscular fat, and transparent tissues, we performed matrix-assisted laser desorption/ionization-mass spectrometry imaging (MALDI-MSI). Eleven diacyl-, seven alkylacyl-, and six alkenylacyl-PCs were identified using liquid chromatography (LC)-tandem MS (MS/MS) analysis. Despite many alkylacyl- and alkenylacyl-PC species sharing identical m/z values, we were able to visualize these PC species using MALDI-MSI. Diacyl- and alkylacyl- and/or alkenylacyl-PC species showed unique distribution patterns in the tissues, suggesting that their distribution patterns were dependent on their fatty acid compositions. PCs are a major dietary source of choline in meat, and the amount was significantly higher in the muscle tissues. Consumption of choline mitigates age-related memory decline and neurodegenerative diseases; therefore, the consumption of pork muscle tissues could help to mitigate these diseases. These results support the use of MALDI-MSI analysis for assessing the association between PC species and the quality parameters of meat.