Raman spectroscopy expands its applications in life science, medicine, pharmacology, agricultural science, and food science, recently. Raman spectroscopy is a strong tool for nondestructive and label free analysis as well as for studies on molecular properties, structures and reactions. The present review introduces the basis and principles of Raman spectroscopy and properties of lipid spectra, and then overviews applications for lipid analyses in food, health and medical sciences.

NIR spectroscopy is an analytical method that utilizes spectra in the 750-2500 nm region and has been developed since the 1970s, mainly in the food industry, because it enables high-throughput measurement of the objects with nondestructive and noninvasive. The determination methods for lipid concentrations in foods and living organisms have been proposed in combination with chemometrics, and a number of instruments specified to lipid analysis have been introduced to the market. Furthermore, since lipid oxidation and abnormalities in lipid status are factors of malignant diseases in vivo, the visualization of lipid concentration in situ combined with near-infrared imaging has been actively considered in the medical field in recent years. In this article, the trends in lipid analysis in the field of near-infrared spectroscopy reviewed through the theory of near-infrared spectroscopy, instrumentation and several applications of quantitative analysis lipids, in addition, distribution analysis using NIR imaging.

On electrospray ionization-mass spectrometry (ESI-MS), several adduct ions such as [M+H]⁺, [M+NH₄]⁺, [M+CH₃COO]^-, [M+Na]⁺, and [M+K]⁺ are observed. Among them, metal adduct ions have been recently focusing for their characteristics that provides unique fragmentation. A coordination position of metal ion is totally different from H⁺ and NH₄ ⁺, and the coordination is considered to be based on cation-π electron interaction. Coordination of metal ion brings the changes of some geometric parameters and binding energies of the ion, which results in strikingly different fragmentation from that of [M+H]⁺ and [M+NH₄]⁺. In this review, we introduced the mechanisms about coordination of metal ion and some examples of structural analysis focusing on lipid.

Recent advances in untargeted lipidomics using mass spectrometry have enabled one to grasp >1,000 lipid molecules from a single specimen. This is largely because of the development of analytical chemistry and its informatics (computational mass spectrometry) research. With other omics data such as transcriptome, the biological importance of various lipids has been revealed. Moreover, untargeted lipidomics can be applied not only in basic science, but also in a wide range of fields, such as biomarker discovery in clinical study and functional analysis in food science. In this review article, we focus on the data analysis part of the untargeted lipidomics workflow and provide the fruitful information to help readers who are interested in starting lipid metabolome analysis. This review contains (1) data processing guideline to extract the lipid profile information from mass spectrometry data, (2) standardization of untargeted lipidomics data, and (3) biological interpretation of lipidomics data by using ontology analysis and pathway analysis.