Lipidomics has been widely used in food lipid composition analysis, quality discrimination, authenticity identification and origin tracing.
Lipids are closely related to the flavor and nutrition of foods. Lipids are not only a major factor influencing the development and processing of food products, but also affect human health. Lipidomics has been widely used to analyze the lipids of food products, laying the foundation for functional component analysis, processing by-product utilization and oil resources development. However, the complex and diverse lipid structures and compositions in foods make it difficult to completely separate heterogeneous lipids and distinguish lipid acyl chain position heterogeneity from double bond position heterogeneity. With the development of lipid separation and detection technology, the analytical ability of lipids has been improved, making it possible to distinguish isomers.
Mass spectrometry-based lipidomics is not only applied in food composition analysis, but also in food quality discrimination. The oxidative hydrolysis of lipids is one of the important factors affecting the nutrition, quality and safety of meat and meat products. Lipidomics can reveal the mechanism of lipid oxidative hydrolysis at the level of lipid molecules, which will help to develop novel techniques to control the oxidative hydrolysis of lipids.
Breastfeeding is generally considered to be the healthiest way to feed infants and young children, but in many cases, it is difficult to achieve and therefore infant formula is needed as an alternative. Lipids provide essential nutrients for the growth and development of infants and young children. There are large differences in triglyceride (TG) composition in breast milk between lactation stages. Lipidomics allows the comparison of long-chain TG and saturated TG content in different infant formulas, thus providing a reference for production or purchase.
The quality and variety of the vinified grapes are important factors in the quality of the wine, and lipidomics also contributes to the technical understanding of viticulture and winemaking.
Fig. 1 Mass spectrometry-based lipidomics in foodomics (Wu et al., 2020)
Adulteration in the modern food industry has seriously interfered with the healthy development of the food industry. The differences in the composition and content of lipids in different food products make lipids a target for food authenticity identification. Lipidomics has been used to screen food lipid markers for the authenticity of edible oils, dairy products and cereals.
High-value cooking oils are often adulterated by low-value cooking oils, and TG profile characteristics can be used to identify the authenticity of cooking oils. The TG profile can be used to identify the authenticity of edible oils more effectively because of the greater variation in TG in different edible oils compared to fatty acid composition. Liquid chromatography-mass spectrometry (LC-MS) can be used to compare the fatty acid, TG and polar lipid composition of extra virgin olive oil and virgin olive oil, and to compare the TG composition of high oleic peanut oil and common peanut oil for rapid identification of authenticity.
Lipidomics has been used in the study of food origin traceability because of the differences in nutritional and economic values of foods due to different origins. The lipid content of foods from different origins may be different. By comparing the levels of each lipid, food origin traceability can be achieved. For example, lipids affect the texture, rheological properties, digestibility and storage stability of cereals and cereal products, and the lipid composition of cereals is closely related to the origin.
Various reactions occur in lipids during food processing, such as thermal oxidation, hydrolysis, thermal polymerization and Merad reaction. Changes in lipids can affect changes in food quality and thus food safety. High-throughput lipidomics combined with chemometric analysis is a powerful technique for analyzing the harmful oxidation products of lipids, monitoring the effects of food processing on lipid composition and the generation of harmful products, and providing new solutions for food quality and safety research.
With the continuous development of chromatographic techniques, ionization methods, mass analyzers and different tandem methods, especially various soft ionization techniques and high-resolution mass spectrometry, the detection methods for lipidomics can be selectively enriched.
ESI and APCI are the commonly used ionization modes for lipidomic analysis; ESI can effectively ionize all types of lipids, while APCI is suitable for the analysis of weakly polar lipids and fatty acids. Triple quadrupole mass spectrometry is the most widely used technique in lipidomics, using either multiple reaction detection scans or precursor ion scans or neutral loss scans for different lipid classes.
In recent years, high-resolution MS has become the first choice for lipidomics analysis, and common high-resolution mass spectrometry techniques include FT-ICR mass spectrometry, Orbitrap mass spectrometry, and TOF mass spectrometry. High-resolution mass spectrometry has higher sensitivity, mass resolution and mass accuracy. It is usually based on high mass resolution and accuracy as well as isotopic abundance combined with secondary fragmentation ion (MS/MS) spectroscopy to identify lipid molecules.
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