Comparison of frozen and fresh apple pulp for NMR-based metabolomic analysis

High-Throughput Metabolomics by 1D NMR

Metabolomics deals with the whole ensemble of metabolites (the metabolome). As one of the -omic sciences, it relates to biology, physiology, pathology and medicine; but metabolites are chemical entities, small organic molecules or inorganic ions. Therefore, their proper identification and quantitation in complex biological matrices requires a solid chemical ground. With respect to for example, DNA, metabolites are much more prone to oxidation or enzymatic degradation: we can reconstruct large parts of a mammoth's genome from a small specimen, but we are unable to do the same with its metabolome, which was probably largely degraded a few hours after the animal's death. Thus, we need standard operating procedures, good chemical skills in sample preparation for storage and subsequent analysis, accurate analytical procedures, a broad knowledge of chemometrics and advanced statistical tools, and a good knowledge of at least one of the two metabolomic techniques, MS or NMR. All these skills are traditionally cultivated by chemists. Here we focus on metabolomics from the chemical standpoint and restrict ourselves to NMR. From the analytical point of view, NMR has pros and cons but does provide a peculiar holistic perspective that may speak for its future adoption as a population-wide health screening technique.

Nuclear Magnetic Resonance (NMR) Spectroscopy in Food Science: A Comprehensive Review

Nuclear magnetic resonance (NMR) spectroscopy is a robust method, which can rapidly analyze mixtures at the molecular level without requiring separation and/or purification steps, making it ideal for applications in food science. Despite its increasing popularity among food scientists, NMR is still an underutilized methodology in this area, mainly due to its high cost, relatively low sensitivity, and the lack of NMR expertise by many food scientists. The aim of this review is to help bridge the knowledge gap that may exist when attempting to apply NMR methodologies to the field of food science. We begin by covering the basic principles required to apply NMR to the study of foods and nutrients. A description of the discipline of chemometrics is provided, as the combination of NMR with multivariate statistical analysis is a powerful approach for addressing modern challenges in food science. Furthermore, a comprehensive overview of recent and key applications in the areas of compositional analysis, food authentication, quality control, and human nutrition is provided. In addition to standard NMR techniques, more sophisticated NMR applications are also presented, although limitations, gaps, and potentials are discussed. We hope this review will help scientists gain some of the knowledge required to apply the powerful methodology of NMR to the rich and diverse field of food science.

Metabolomic characterization of pitaya fruit from three red-skinned cultivars with different pulp colors

Pitaya is a new fruit crop, whose exotically colored fruits have excellent nutritional and antioxidant properties. In this study, the primary metabolite profiles of three pitaya cultivars i.e. 'Guanhuahong' (red peel with red pulp), 'Guanhuabai' (red peel with white pulp) and 'Guanhuahongfen' (red peel with pink pulp) were investigated using GC-MS and Ultraviolet-visible spectroscopy. In the fruit pulp, levels of starch, organic acids, and inositol decreased as the fruit matured. Glucose, fructose, sucrose and sorbitol contents increased gradually during fruit maturation and reached their highest levels in the pulp at the mature stage. Citramalic acid was identified for the first time in the pulp of Hylocereus species. Higher levels of total phenols, flavonoids and antioxidant activities were detected in the peel than in the pulp during fruit maturation of all three cultivars. The finding of higher levels of total phenols and flavonoids in the pitaya peel than in the pulp at the mature stage suggests that pitaya peels are a good source of natural phenols and flavonoids.