Analysis of food proteins and peptides by chromatography and mass spectrometry

The research topics and the analytical strategies dealing with food proteins and peptides are summarized. Methods for the separation and purification of macromolecules of food concern by both high-performance liquid chromatography (HPLC) on conventional packings and perfusion HPLC are examined. Special attention is paid to novel methodologies such those based on multi-dimensional systems that comprise liquid-phase based protein separation, protein digestion and mass spectrometry (MS) analysis of food peptide and proteins. Recent applications of chromatography and MS-based techniques for the analysis of proteins and peptides in food are discussed.     

液相色谱-高分辨质谱联用技术在食品欺诈检测鉴别中的应用

针对我国现阶段较为突出的违法使用农兽药、滥用食品添加剂、非法添加非食用物质和掺杂使假等食品欺诈问题,综述了近5年来液相色谱-高分辨质谱联用技术在该领域的应用情况。重点介绍了高分辨质谱,主要是飞行时间质谱和静电场轨道阱质谱技术的定向筛查和非定向筛查功能在食品欺诈检测鉴别中的应用,以期为解决该类食品安全问题提供有益的参考。     

Recent applications of gas chromatography with high‐resolution mass spectrometry

Gas chromatography coupled to high‐resolution mass spectrometry is a powerful analytical method that combines excellent separation power of gas chromatography with improved identification based on an accurate mass measurement. These features designate gas chromatography with high‐resolution mass spectrometry as the first choice for identification and structure elucidation of unknown volatile and semi‐volatile organic compounds. Gas chromatography with high‐resolution mass spectrometry quantitative analyses was previously focused on the determination of dioxins and related compounds using magnetic sector type analyzers, a standing requirement of many international standards. The introduction of a quadrupole high‐resolution time‐of‐flight mass analyzer broadened interest in this method and novel applications were developed, especially for multi‐target screening purposes. This review is focused on the development and the most interesting applications of gas chromatography coupled to high‐resolution mass spectrometry towards analysis of environmental matrices, biological fluids, and food safety since 2010. The main attention is paid to various approaches and applications of gas chromatography coupled to high‐resolution mass spectrometry for non‐target screening to identify contaminants and to characterize the chemical composition of environmental, food, and biological samples. The most interesting quantitative applications, where a significant contribution of gas chromatography with high‐resolution mass spectrometry over the currently used methods is expected, will be discussed as well.     

Characterisation of modified whey protein in milk ingredients by liquid chromatography coupled to electrospray ionisation mass spectrometry

Whey proteins are an important ingredient in the food industry. We have investigated the protein composition of commercial whey samples by liquid chromatography coupled to electrospray ionisation mass spectrometry on a time-of-flight instrument. We found that industrial whey protein contains a multitude of different modifications, ranging from almost native proteins through different degrees of glycosylation and oxidation up to almost completely oxidised forms. The information obtained allows characterisation of the influence of industrial processing on protein modifications and classification of whey protein-based ingredients or milk powders from different suppliers.     

Application of gas and liquid chromatography coupled to time‐of‐flight mass spectrometry in pesticides: Multiresidue analysis

Analysis of pesticide residues in water and food matrices is an active research area closely related to food safety and environmental issues. In this aspect mass spectrometry (MS) coupled to gas chromatography (GC) and liquid chromatography (LC) has been increasingly used in the analysis of pesticide residues in water and food. The increasing interest in application of high‐resolution mass spectrometry with time‐of‐flight (TOF) and hybrid triple quadrupole TOF in pesticide analysis is due to its capability of performing both targeted and nontargeted analysis. This article discusses an overview of the application of GC‐TOF‐MS and LC‐TOF‐MS in water and food matrices.     

Multidimensional detection methods for separations and their application in food analysis

The use of the multidimensional detection systems, mass spectrometry and NMR, with separation techniques is discussed with a consideration of their actual or potential application in food analysis. The features of the most commonly used interfaces for coupling liquid chromatography (LC) and mass spectrometry (MS) are briefly examined and examples from the literature on the use of LC-MS in the analysis of natural components in foodstuffs are reported. The potential capabilities for food analysis of LC-NMR, supercritical fluid chromatography (SFC)-MS and capillary electrophoresis (CE)-MS are highlighted.     

模式识别在食品质量控制方面的应用进展

本文介绍了食品质量研究中常用的一些化学模式识别方法的基本原理,并介绍了模式识别结合红外、原子吸收、原子发射、气相色谱、液相色谱、质谱、电子鼻传感器等检测技术在食品质量控制中的应用.对化学计量学在食品质量控制中的应用前景作了展望.     

Simultaneous quantitation of 17 female sex hormones in illegal products by validated liquid chromatography-high resolution mass spectrometry and liquid chromatography-tandem mass spectrometry methods

The consumption of food and drugs adulterated with female sex hormones can have an extremely adverse effect on human health. Therefore, developing appropriate monitoring methods for the identification of various exogenous female sex hormones is crucial for minimizing and eliminating the related health risks. Herein, 17 female hormones categorized into two groups: estrogen and progestin, were analyzed using reversed-phase liquid chromatography coupled to Orbitrap or triple quadrupole mass spectrometry. The fragmentation patterns for all compounds were discovered, and fragmented structures were also derived from them through liquid chromatography–high-resolution mass spectrometry followed by qualitative sample analysis. In addition, a quantitative analysis of 67 samples of illicit drugs and dietary supplements was performed using the validated liquid chromatography-tandem mass spectrometry method. Female hormone components were detected in two samples of an unauthorized injectable solution and a tablet-type drug. Medroxyprogesterone was detected in the samples in the range of 96.4–206 ng/g. Notably, eight components similar in structure to steroids were simultaneously detected as male sex hormones by confirming their fragmentation ion patterns using liquid chromatography–high-resolution mass spectrometry. The developed methods thus offer a dependable and practically applicable approach for the screening and detection of exogenous female sex hormones in real food and drug samples to ensure public health.     

Direct ionization methods in mass spectrometry: An overview

Within this paper a sub-group of ambient ionization mass spectrometry namely direct ionization mass spectrometry techniques are reviewed. They are characterized by the generation of an electrospray directly from the sample investigated. Prominent representatives include paper spray mass spectrometry, tissue spray mass spectrometry, probe electrospray ionization or thin-layer chromatography mass spectrometry. Applications of all major direct ionization techniques within different fields such as biomedical analysis, analysis of natural products, analysis of technical products and food analysis, just to name a few, are discussed and relevant parameters are listed in five Tables.     

Multidimensional nano-HPLC for analysis of protein complexes

The analysis of macromolecular protein complexes is an important factor in understanding most cellular processes, e.g., protein transport into cell organells, signal transduction via biological membranes, apoptosis, energy metabolism, directed motion of cells, and cell division. These complexes are not only built of various numbers of different proteins but also of prosthetic groups and RNA molecules. To understand the role each protein plays in a complex, a complete analysis of all protein compounds is necessary. Therefore, several separation steps have to be coupled to mass spectrometry to identify the proteins. In this work, we describe the application of multidimensional liquid chromatography, SCX-RP-LC as well as SAX-RP-LC, coupled to electrospray ion trap mass spectrometry. Tryptic digested ribosomes were separated by ion exchange chromatography manually collected and prepared for reversed phase chromatography to analyze the peptides via nano-ESI mass spectrometry. The total numbers of identified proteins are compared in consideration of the separation method (SCX-RP versus SAX-RP).     

Adding a new separation dimension to MS and LC–MS: What is the utility of ion mobility spectrometry?

Ion mobility spectrometry is an analytical technique known for more than 100 years, which entails separating ions in the gas phase based on their size, shape, and charge. While ion mobility spectrometry alone can be useful for some applications (mostly security analysis for detecting certain classes of narcotics and explosives), it becomes even more powerful in combination with mass spectrometry and high‐performance liquid chromatography. Indeed, the limited resolving power of ion mobility spectrometry alone can be tackled when combining this analytical strategy with mass spectrometry or liquid chromatography with mass spectrometry. Over the last few years, the hyphenation of ion mobility spectrometry to mass spectrometry or liquid chromatography with mass spectrometry has attracted more and more interest, with significant progresses in both technical advances and pioneering applications. This review describes the theoretical background, available technologies, and future capabilities of these techniques. It also highlights a wide range of applications, from small molecules (natural products, metabolites, glycans, lipids) to large biomolecules (proteins, protein complexes, biopharmaceuticals, oligonucleotides).     

Identification of RP-HPLC peaks of bisphenol F and of bisphenol F diglycidyl ether and its hydrolysis products by thermospray mass spectrometry and gas chromatography/mass spectrometry

Summary The need to determine the migration of toxic unreacted compounds in bisphenol diglycidyl ether epoxy resins prompted us to investigate the HPLC properties of bisphenol F diglycidyl ether and its hydrolysis products in the water-based food simulants 3% (w/v) acetic acid, distilled water and 15% (v/v) ethanol. Peaks were identified by reversed-phase HPLC thermospray mass spectrometry and gas chromatography/mass spectrometry.     

Recent advances in the application of mass spectrometry in food-related analysis

A review is presented on recent applications of mass spectrometry (MS)-based techniques for the analysis of compounds of food concern. Substances discussed are naturally occurring compounds in food products such as lipids, oligosaccharides, proteins, vitamins, flavonoids and related substances, phenolic compounds and aroma compounds. Among xenobiotics, applications of MS techniques for the analysis of pesticides, drug residues, toxins, amines and migrants from packaging are overviewed. Advances in the analysis of trace metals of nutritional and toxicological interest by MS with inductively coupled plasma (ICP) source are presented. The main features of mass spectrometry combined with separation instruments are discussed in food-related analysis. Examples of mass spectrometry and tandem MS (MS-MS) are provided. The development and application of matrix-assisted laser desorption ionization (MALDI) and electrospray (ESI) to the analysis of peptides and proteins in food is discussed. This survey will attempt to cover the state-of-the-art up from 1999 to 2001.     

食品中邻苯二甲酸酯类化合物的分析方法研究进展

邻苯二甲酸酯是应用最广泛的增塑剂,具有生殖、发育毒性及致癌性,是近年来食品污染的一个重要来源。该类化合物种类多、同系物和同分异构体性质接近、在基体中含量范围宽,高效样品前处理、高选择性分离和高灵敏检测、降低本底干扰等技术是食品中邻苯二甲酸酯类化合物准确测定面临的挑战。本文综述了液液萃取、液液微萃取、固相萃取、固相微萃取、基质固相萃取等传统及新型的提取与净化技术在食品样品分析中的应用,比较分析了气相色谱、液相色谱、串联质谱、高分辨质谱以及酶联免疫、离子迁移谱等快速检测技术的特点,并展望了发展趋势。     

Comparative study of ink photoinitiators in food packages using gas chromatography with vacuum ultraviolet detection and gas chromatography with mass spectrometry

This work focused on the development and validation of the analytical procedure using gas chromatography equipped with vacuum‐ultraviolet detection for the specific and sensitive determination of nine photoinitiators in food packages. Subsequently, a comparison of the combination of vacuum ultraviolet spectroscopy with gas chromatography and a developed gas chromatography with mass spectrometry method was performed. The vacuum‐ultraviolet spectra of all tested photoinitiators were collected and found to be highly distinct, even for isomers. Under the optimal conditions, the limits of detection for nine photoinitiators ranged from 1 to 5 mg/L using vacuum ultraviolet detection and from 0.15 to 0.5 mg/L using mass spectrometric detection. Both techniques were successfully applied for screening of photoinitiators in seven kinds of food packages and the obtained data showed good agreement (the relative difference was between 3 and 18%). The variability in concentrations found in triplicate samples was assessed to be below 18%. Predominantly benzophenone was found in all analysed samples in the range of 0.31–4.23 mg/kg. It appears to be preferably selected by food packaging manufacturers. This study proposes a new simple and sensitive technique used for analysis of photoinitiators that could be a good alternative to gas chromatography with mass spectrometry.     

A pilot study (APMP.QM-P19) for the measurement of melamine in milk powder

A pilot study (APMP.QM-P19) of the Asia Pacific Metrology Program for the determination of melamine at two different levels in milk powder was organized in 2010. It was the first interlaboratory comparison programme in measuring melamine in food matrices for metrology institutes in the region. Melamine was chosen as the target analyte because of the recent crises that happened in 2007 and 2008 had caused substantial concern from consumers, food manufacturers, policy makers on food safety and the food testing communities. The objectives of APMP.QM-P19 were to evaluate the testing capability of participants on the quantification of trace level melamine in milk and milk products and to investigate the degree of equivalence with respect to the assigned values. In total, 19 laboratories (11 metrology institutes and eight food testing institutes) enrolled in the study. Analytical techniques reported by participants included liquid chromatography with ultra-violet and tandem mass spectrometry, gas chromatography with high-resolution mass spectrometry and enzyme-linked immunosorbent assay. Dispersion of analytical data in the two test materials was significant, and normal Gaussian distribution of data was not observed. The median was agreed to be used as the assigned values in the programme. Metrology institutes who employed isotope dilution mass spectrometry technique were found to give more consistent results and higher degree of equivalence than others. The performance of most of the food testing institutes was not satisfactory, and they were encouraged to have a thorough review of their validation procedure and estimation of uncertainty.     

Mass spectrometric approach for the analysis of food proteins

In the study of food proteins, the need for accurate protein structural analysis has been acknowledged because of the fact that nucleotide sequencing alone is of limited analytical value if not combined with relevant information regarding the specific protein expressed and the occurrence of phosphorylation, glycosylation and disulphide bridges, and with the modification induced by the technological treatment. Mass spectrometry, whether used alone or to complement the traditional molecular-based techniques has become fundamental to the structural analysis of proteins. It is, moreover, virtually irreplaceable in determining post-translational modifications as conventional methods cannot deliver reliable data. What lies at the root of this methodological breakthrough is the combination of high-resolution separation techniques such as two-dimensional electrophoresis or capillary reverse- phase high-performance liquid chromatography with mass spectrometric analysis, what is termed "proteomic" analysis. Thus, it appears appropriate to state that the new mass spectrometric techniques have been established as a valuable and efficient tool for protein and peptide analysis in complex mixtures, like those from food matrices, enabling us therefore to provide accurate information on molecular weight and also to put forth a structural assessment at a low-picomole level of material. Thus, a series of alternative approaches have been developed based on advanced mass spectrometric analysis in conjunction with classic protein chemistry in order to provide an in-depth view of food protein structure. This review outlines several of these novel methodologies as they apply to structural characterization of food products.     

Application of hyphenated techniques to the chromatographic authentication of flavors in food products and perfumes

This work presents two techniques for testing for the adulteration of flavors. One uses multidimensional gas chromatography on cyclodextrin derivatives to separate chiral compounds, the other uses isotope ratio mass spectrometry coupled with gas chromatography to determine stable isotope ratios. Applications to fruits and plants for the food and perfume industry are introduced.     

Linking protein fractionation with multidimensional monolithic reversed-phase peptide chromatography/mass spectrometry enhances protein identification from complex mixtures even in the presence of abundant proteins

Recently, multidimensional shotgun proteomics has proven to be an alternative technology able to identify hundreds of proteins from single samples. Two major limitations of the technology are the presence of high abundance proteins (e.g. RUBISCO in plant leaf tissue) and the enormous number of co-eluting peptides that overstrain the loading and resolving capacity of conventional particle-packed columns as well as the capacity of electrospray ionisation due to ion suppression. Here, the coupling of fast performance liquid chromatography (FPLC) pre-fractionation of an Arabidopsis leaf protein extract and subsequent two-dimensional liquid chromatography/mass spectrometry with improved resolution using a monolithic silica C18 capillary column allowed the identification of 1032 unique proteins in a single 4 mg total protein plant leaf tissue sample. The reassignment of peptide IDs to distinct FPLC protein fractions enhances the identification procedure, especially in the case of present protein isoforms. The proposed strategy is useful to detect proteins otherwise not seen in conventional multidimensional chromatography/mass spectrometry approaches.     

Analysis of food proteins and peptides by mass spectrometry-based techniques

Mass spectrometry has arguably become the core technology for the characterization of food proteins and peptides. The application of mass spectrometry-based techniques for the qualitative and quantitative analysis of the complex protein mixtures contained in most food preparations is playing a decisive role in the understanding of their nature, structure, functional properties and impact on human health. The application of mass spectrometry to protein analysis has been revolutionized in the recent years by the development of soft ionization techniques such as electrospray ionization and matrix assisted laser desorption/ionization, and by the introduction of multi-stage and ‘hybrid’ analyzers able to generate de novo amino acid sequence information. The interfacing of mass spectrometry with protein databases has resulted in entirely new possibilities of protein characterization, including the high sensitivity mapping (femtomole to attomole levels) of post-translational and other chemical modifications, protein conformations and protein–protein and protein–ligand interactions, and in general for proteomic studies, building up the core platform of modern proteomic science. MS-based strategies to food and nutrition proteomics are now capable to address a wide range of analytical questions which include issues related to food quality and safety, certification and traceability of (typical) products, and to the definition of the structure/function relationship of food proteins and peptides. These different aspects are necessarily interconnected and can be effectively understood and elucidated only by use of integrated, up-to-date analytical approaches. In this review, the main aspects of current and perspective applications of mass spectrometry and proteomic technologies to the structural characterization of food proteins are presented, with focus on issues related to their detection, identification, and quantification, relevant for their biochemical, technological and toxicological aspects.