Abstract

With the rising demand for healthier food and the expanding concerns about environmental sustainability, the global trends of organic vegetable consumption are rapidly increasing.1 Mislabelling is the major food fraud in organic agriculture because of the absence of reliable analytical evidence for organic origin authentication. Lipidomics is one of the potential solutions because the lipid composition of the plant is highly affected by numerous environmental factors, such as temperature, pests and nutrients.2 In the present work, we investigate the difference in lipid profile among seven common types of Chinese leafy vegetables and the influence of organic farming using an untargeted lipidomics platform on ultra-high-performance liquid chromatography-Orbitrap-mass spectrometry (UPLC-Orbitrap-MS) with detailed mass fragmentation analysis. The difference in lipid profile among seven vegetables is family-dependent. The vegetables from the same family share the lipid profile with a higher similarity. White and green stalked water spinach from the Convolvulaceae family showed the highest abundance of palmitic acid and palmitic acid-containing phospholipids. Chinese kale and choy sum from the Cruciferae family have the highest content of unsaturated fatty acyl-containing glucosylceramide, monogalactosyl diacylglycerols (MGDGs) and sulfoquinovosyl diacylglycerols (SQDGs). Lettuce and Indian lettuce from the Asteraceae family showed the highest contents of linolenic acid-containing SQDGs. Red amaranth from the Amaranthaceae family showed the highest concentration of glycerides containing two linoleic acid chains. In contrast to the type of vegetables, the influence of organic farming is family-independent. Glycerides are the most influential lipid class between organic and conventional leafy vegetables. Four types of Chinese leafy vegetables, including Chinese kale, Indian lettuce, lettuce and white stalked water spinach, have lower glyceride content in organic farming than their conventional counterparts, while both choy sum and green stalked water spinach from organic farming have higher glyceride content. Photosynthesis-related lipids, MGDGs and SQDGs, with unsaturated fatty acid chains also showed higher abundance in organic leafy vegetables. Our results suggest that the lipidomics approach is potentially applied to developing a routine analytical-based organic food traceability system.

1Willer, H.; Schlatter, B.; Trávníček, J.; Kemper, L. and Lernoud, J., “The World of Organic Agriculture. Statistics and Emerging Trends 2020.,” 2020.

2 Mwamba, T. M.; Islam, F.; Ali, B.; Lwalaba, J. L. W.; Gill, R. A.; Zhang, F.; … & Wang, J., Chemosphere, 2020, 250, 126308.