Preliminary approaches for the development of a high-performance liquid chromatography/electrospray ionization tandem mass spectrometry method for the detection and label-free semi-quantitation of the main storage proteins of Lupinus albus in foods

Lupine allergens: Clinical relevance, molecular characterization, cross-reactivity, and detection strategies

Lupine is commonly utilized as a technological food and ingredient in a great variety of processed products (snacks, bakery, meat, and dairy products) principally owing to its nutritional value and technological properties. However, its ingestion, even at trace amounts (in the range of mg protein per kg of food), can lead to severe adverse reactions in allergic individuals. Lupine belongs to the Leguminosae family, having the conglutins (α-, β-, δ-, and γ-) as allergens, among other proteins. Cross-sensitization of lupine-sensitized individuals with other legume species, mainly peanut, can occur, but the associated clinical reactivity is still unclear. The protection of the sensitized individuals should depend on an avoidance diet, which should rely on the compliance of food labeling and, as such, on their verification by analytical methods. Food processing, such as heat treatments, has an important influence on the structural properties of lupine proteins, altering their detectability and allergenicity. In this review, different aspects related with lupine allergy are described, namely, the overall prevalence, clinical relevance, diagnosis, and treatment. The characterization of lupine allergens and their potential cross-reactivity with other legumes are critically discussed. The effects of food matrix, processing, and digestibility on lupine proteins, as well as the available analytical tools for detecting lupine at trace levels in foods, are also herein emphasized.

Analysis of Narrow-Leaf Lupin Proteins in Lupin-Enriched Pasta by Untargeted and Targeted Mass Spectrometry

The supplementation of different food items with grain legumes and, in particular, with lupin has been demonstrated to provide useful health benefits, especially in the area of cardiovascular disease prevention. In this work, label free quantitative untargeted and targeted approaches based on liquid chromatography−electrospray ionization−tandem mass spectrometry (LC−ESI−MS/MS) for investigating the protein profile of three pasta samples containing different percentages of narrow-leaf lupin flour were carried out. The untargeted method permitted the identification of the main acidic globulins (α-conglutin, β-conglutin, and δ-conglutin) and the comparison of their profile with raw lupin flour. The targeted method, based on High-performance liquid chromatography electrospray ionization tandem mass spectrometry HPLC-Chip-Multiple Reaction Monitoring (MRM) mode, allowed the quantification of γ-conglutin, the main hypoglycemic component of lupin protein: its concentration was around 2.25 mg/g in sample A, 2.16 mg/g in sample D, and 0.57 mg/g in sample F.

Proteomics for exploiting diversity of lupin seed storage proteins and their use as nutraceuticals for health and welfare

Lupins have a variety of both traditional and modern uses. In the last decade, reports assessing the benefits of lupin seed proteins have proliferated and, nowadays, the pharmaceutical industry is interested in lupin proteins for human health. Modern genomics and proteomics have hugely contributed to describing the diversity of lupin storage genes and, above all, proteins. Most of these studies have been centered on few edible lupin species. However, Lupinus genus comprises hundreds of species spread throughout the Old and New Worlds, and these resources have been scarcely explored and exploited. We present here a detailed review of the literature on the potential of lupin seed proteins as nutraceuticals, and the use of -omic tools to analyze seed storage polypeptides in main edible lupins and their diversity at the Lupinus inter- and intra-species level. In this sense, proteomics, more than any other, has been a key approach. Proteomics has shown that lupin seed protein diversity, where post-translational modifications yield a large number of peptide variants with a potential concern in bioactivity, goes far beyond gene diversity. The future extended use of second and third generation proteomics should definitely help to go deeper into coverage and characterization of lupin seed proteome.

BIOLOGICAL SIGNIFICANCE

Some important topics concerning storage proteins from lupin seeds are presented and analyzed in an integrated way in this review. Proteomic approaches have been essential in characterizing lupin seed protein diversity, which goes far beyond gene diversity since the protein level adds to the latter differential proteolytic cleavage of conglutin pro-proteins and a diverse array of glycosylation forms and sites. Proteomics has also proved helpful for screening and studying Lupinus germplasm with the future aim of exploiting and improving food production, quality, and nutritional values.

Rapid shotgun proteomic liquid chromatography-electrospray ionization-tandem mass spectrometry-based method for the lupin ( Lupinus albus L.) multi-allergen determination in foods

Allergy to lupin is a growing food safety problem because this legume, increasingly exploited in the food industry, is one of the allergens that, according to law, must be declared on the labels of food products in the European Union. In this context, a rapid targeted proteomic approach based on liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) analysis was proposed and aimed to unequivocal confirmation and reliable determination of the major lupin allergens, i.e., conglutins, in pasta and biscuits. Detected concentrations were around 1 mg of lupin/kg of pasta and biscuits, proving the capabilities of the MS-based method in terms of the sensitive allergen screening method. Good precision was observed in terms of both intra- and interday repeatability, with relative standard deviation (RSD) lower than 23%. Recoveries from 95 ± 10 to 118 ± 12% and from 103 ± 1 to 110 ± 12% ranges were calculated for biscuits and pasta, respectively. Finally, the applicability of the devised method was investigated by analyzing market samples containing lupin and samples that may possibly contain traces of lupin deriving from cross-contamination between products and production lines.

Liquid chromatography and mass spectrometry in food allergen detection

Food allergy is an important issue in the field of food safety because of the hazards for affected persons and the hygiene requirements and legal regulations imposed on the food industry. Consumer protection and law enforcement require suitable analytical techniques for the detection of allergens in foods. Immunological methods are currently preferred; however, confirmatory alternatives are needed. The determination of allergenic proteins by liquid chromatography and mass spectrometry has greatly advanced in recent years, and gel-free allergenomics is becoming a routinely used approach for the identification and quantitation of food allergens. The present review provides a brief overview of the principles of proteomic procedures, various chromatographic set ups, and mass spectrometry instrumentation used in allergenomics. A compendium of published liquid chromatography methods, proteomic analyses, typical marker peptides, and quantitative assays for 14 main allergy-causing foods is also included.

Size exclusion chromatography coupled to electrospray ionization mass spectrometry for analysis and quantitative characterization of arsenic interactions with peptides and proteins

Arsenic-binding proteins are of toxicological importance since enzymatic activities can be blocked by arsenic interactions. In the present work, a novel methodology based on size exclusion chromatography coupled to electrospray ionization mass spectrometry (SEC-ESI-MS) was developed with special emphasis to preserve the intact proteins and their arsenic bindings. The eluent composition of 25 mMTris/HCl, pH 7.5, with the addition of 100-mM NaCl optimized for SEC with UV detection provided the highest SEC separation efficiency, but was not compatible with the ESI-MS because of the non-volatility of the buffer substance and of the salt additive. In order to find the best compromise between chromatographic separation and ionization of the arsenic-binding proteins, buffer type and concentration, pH value, portion of organic solvent in the SEC eluent as well as the flow rate were varied. In the optimized procedure five different arsenic-binding peptides and proteins (glutathione, oxytocin, aprotinin, alpha-lactalbumin, thioredoxin) covering a molar mass range of 0.3-14 kDa could be analyzed using 75% 10-mM ammonium formate, pH 5.0/25% acetonitrile (v : v) as eluent and a turbo ion spray source operated at 300 degrees C and 5.5 kV. A complete differentiation of all peptides and proteins involved in the arsenic-binding studies as well as of their arsenic-bound forms has become feasible by means of the extracted ion chromatograms (XIC) of the mass spectrometric detection. The new method offered the possibility to estimate equilibrium constants for the reaction of phenylarsine oxide with different thiol-containing biomolecules by means of the XIC peak areas of reactants and products. Limits of detection in the range of 2-10 microM were obtained by SEC-ESI-MS for the individual proteins.

Parameters for the evaluation of the thermal damage and nutraceutical potential of lupin-based ingredients and food products

Foods based on sweet lupin proteins are gaining attention from industry and consumers because of their possible role in the prevention of cardiovascular disease. When promoting lupin-based foods for inclusion in a daily diet, the thermal damage suffered during processing is of relevance to the bioactive and nutritional quality of the food product. N-(2-furoylmethyl)-L-lysine (furosine) quantification demonstrates that currently available sweet lupin protein isolates have a thermal damage comparable to or lower than other traditional food ingredients, and are a good source of lysine in non-dairy products. In lupin-based foods claiming to have cholesterol-lowering potential, shotgun proteomics offers itself as a fast and effective screening method for assessing the biological availability of active peptides. Such a method is readily applicable to other legume-enriched food products.