In-house validation of an LC-MS method for the multiplexed quantitative determination of total allergenic food in chocolate

Mass spectrometry has been widely accepted as a confirmatory tool for the sensitive detection of undeclared presence of allergenic ingredients. Multiple methods have been developed so far, achieving different levels of sensitivity and robustness, still lacking harmonization of the analytical validation and impairing comparability of results. In this investigation, a quantitative method has been validated in-house for the determination of six allergenic ingredients (cow's milk, hen's egg, peanut, soybean, hazelnut, and almond) in a chocolate-based matrix. The latter has been produced in a food pilot plant to provide a real and well-characterized matrix for proper assessment of method performance characteristics according to official guidelines. In particular, recent considerations issued by the European Committee for Standardization have been followed to guide a rigorous single-laboratory validation and to feature the main method performance, such as selectivity, linearity, and sensitivity. Synthetic surrogates of the peptide markers have been used both in native and labelled forms in matrix-matched calibration curves as external calibrants and internal standards, respectively. A two-order of magnitude range was investigated, focusing on the low concentration range for proper assessment of the detection and quantification limits (LOD and LOQ) by rigorous calibration approach. Conversion factors for all six allergenic ingredients have been determined for the first time to report the final quantitative information as fraction of total allergenic food protein (TAFP) per mass of food (µgTAFP/gfood), since such a reporting unit is exploitable in allergenic risk assessment plans. The method achieved good sensitivity with LOD values ranging between 0.08 and 0.2 µgTAFP/gfood, for all ingredients besides egg and soybean, whose quantitative markers reported a slightly higher limit (1.1 and 1.2 µgTAFP/gfood, respectively). Different samples of chocolate bar incurred at four defined concentration levels close to the currently available threshold doses have been analyzed to test the quantitative performance of the analytical method, with a proper estimate of the measurement uncertainty from different sources of variability. The sensitivity achieved resulted in compliance with the various threshold doses issued or recommended worldwide.

Standardization of a Mass Spectrometry-Based Workflow for Food Allergen Quantification

In this chapter, the analytical workflow typically used for the development and validation of an analytical method tailored to food allergen detection and quantification is presented. The main steps defining the workflow are herein described and commented with specific notes about the critical issues that can be faced and common solutions to be adopted. References to guidelines and/or recommendation available from official bodies, as well as main papers from international consortia operating on the specific research field, are also reported, whenever possible. As such, this chapter may represent a practical guide to drive method development in the standardization of analytical methods for food allergen detection.

Alternative Protein Sources and Novel Foods: Benefits, Food Applications and Safety Issues

The increasing size of the human population and the shortage of highly valuable proteinaceous ingredients has prompted the international community to scout for new, sustainable, and natural protein resources from invertebrates (e.g., insects) and underutilized legume crops, unexploited terrestrial and aquatic weeds, and fungi. Insect proteins are known for their nutritional value, being rich in proteins with a good balance of essential amino acids and being a valuable source of essential fatty acids and trace elements. Unconventional legume crops were found rich in nutritional, phytochemical, and therapeutic properties, showing excellent abilities to survive extreme environmental conditions. This review evaluates the recent state of underutilized legume crops, aquatic weeds, fungi, and insects intended as alternative protein sources, from ingredient production to their incorporation in food products, including their food formulations and the functional characteristics of alternative plant-based proteins and edible insect proteins as novel foods. Emphasis is also placed on safety issues due to the presence of anti-nutritional factors and allergenic proteins in insects and/or underutilized legumes. The functional and biological activities of protein hydrolysates from different protein sources are reviewed, along with bioactive peptides displaying antihypertensive, antioxidant, antidiabetic, and/or antimicrobial activity. Due to the healthy properties of these foods for the high abundance of bioactive peptides and phytochemicals, more consumers are expected to turn to vegetarianism or veganism in the future, and the increasing demand for such products will be a challenge for the future.

Development of incurred chocolate bars and broth powder with six fully characterised food allergens as test materials for food allergen analysis

The design and production of incurred test materials are critical for the development and validation of methods for food allergen analysis. This is because production and processing conditions, together with the food matrix, can modify allergens affecting their structure, extractability and detectability. For the ThRAll project, which aims to develop a mass spectrometry-based reference method for the simultaneous accurate quantification of six allergenic ingredients in two hard to analyse matrices. Two highly processed matrices, chocolate bars and broth powder, were selected to incur with six allergenic ingredients (egg, milk, peanut, soy, hazelnut and almond) at 2, 4, 10 and 40 mg total allergenic protein/kg food matrix using a pilot-scale food manufacturing plant. The allergenic activity of the ingredients incurred was verified using food-allergic patient serum/plasma IgE, the homogeneity of the incurred matrices verified and their stability at 4 °C assessed over at least 30-month storage using appropriate enzyme-linked immunosorbent assays (ELISA). Allergens were found at all levels from the chocolate bar and were homogenously distributed, apart from peanut and soy which could only be determined above 4 mg total allergenic ingredient protein/kg. The homogeneity assessment was restricted to analysis of soy, milk and peanut for the broth powder but nevertheless demonstrated that the allergens were homogeneously distributed. All the allergens tested were found to be stable in the incurred matrices for at least 30 months demonstrating they are suitable for method development.

In Vivo and In Vitro Assessment and Proteomic Analysis of the Effectiveness of Physical Treatments in Reducing Allergenicity of Hazelnut Proteins

Hazelnut is a widespread nut species, especially present in Europe, that can be consumed raw or roasted thanks to its pleasant taste and nutritional properties. In addition to renowned beneficial properties hazelnuts contain several proteins capable of inducing food allergy in sensitized individuals, including Cor a 2 (a profilin), Cor a 8 (a lipid transfer protein), Cor a 9 (an 11S seed storage globulin, legumin-like), and Cor a 11 (a 7S seed storage globulin, vicilin-like). In the present paper we investigated the effectiveness of autoclave-based treatments in decreasing the allergic potential of hazelnut as assessed by submitting the treated material to an in vivo skin prick test and an in vitro immunoblot analysis, with sera of allergic individuals exposed to the treated food material. This preliminary analysis showed that autoclave treatment preceded by hydration and/or followed by drying seems to be a promising approach and appears to be effective in reducing the allergenicity of hazelnuts in most patients, probably due to the denaturation of most major and minor allergenic proteins. This work opens up the opportunity to produce hypoallergenic hazelnut derivatives that can be tolerated by allergic subjects.

Optimization of an Untargeted DART-HRMS Method Envisaging Identification of Potential Markers for Saffron Authenticity Assessment

Saffron is one of the most expensive agricultural products in the world and as such, the most commonly adulterated spice, with undeclared plant-based surrogates or synthetic components simulating color and morphology. Currently, saffron quality is certificated in the international trade market according to specific ISO guidelines, which test aroma, flavor, and color strength. However, it has been demonstrated that specific adulterants such as safflower, marigold, or turmeric up to 20% (w/w) cannot be detected under the prescribed approach; therefore, there is still a need for advanced and sensitive screening methods to cope with this open issue. The current investigation aims to develop a rapid and sensitive untargeted method based on an ambient mass spectrometry ionization source (DART) and an Orbitrap™high-resolution mass analyzer to discriminate pure and adulterated saffron samples with either safflower or turmeric. The metabolic profiles of pure and adulterated model samples prepared at different inclusion levels were acquired. Unsupervised multivariate analysis was carried out based on hierarchical cluster analysis and principal component analysis as first confirmation of the discriminating potential of the metabolic profile acquired under optimized DART-HRMS conditions. In addition, a preliminary selection of potential markers for saffron authenticity was accomplished, identifying compounds able to discriminate the type of adulteration down to a concentration level of 5%.

Allergenicity assessment of the edible cricket Acheta domesticus in terms of thermal and gastrointestinal processing and IgE cross-reactivity with shrimp

The allergenic potency of the cricket Acheta domesticus, a promising edible insect, has never been assessed. This work aims to study the immunoreactivity of Acheta domesticus, and its cross-reactivity with the shrimp Litopenaeus vannamei, assessing the effect of cooking and gastrointestinal digestion on their allergenic properties. Different cricket proteins were detected by immunoblotting with shrimp-allergic patients' sera. Tropomyosin was identified as the most relevant IgE-binding protein, and its cross-reactivity with shrimp tropomyosin was demonstrated by ELISA. While shrimp tropomyosin showed scarce stability to gastric digestion, cricket tropomyosin withstood the whole digestion process. The sarcoplasmic calcium-binding protein, specifically detected in shrimp, showed exceptional stability to gastrointestinal digestion. IgE-binding proteins in a model of enriched baked products were partially protected from proteolysis. In conclusion, the ingestion of A. domesticus proteins poses serious concerns to the Crustacean-allergic population. The high stability of tropomyosin may represent a risk of primary sensitization and clinical cross-reactivity.

Prototype Gluten-Free Breads from Processed Durum Wheat: Use of Monovarietal Flours and Implications for Gluten Detoxification Strategies

In this investigation, we reported the production of prototype breads from the processed flours of three specific Triticum turgidum wheat genotypes that were selected in our previous investigation for their potential low toxic/immunogenic activity for celiac disease (CD) patients. The flours were subjected to sourdough fermentation with a mixture of selected Lactobacillus strains, and in presence of fungal endoproteases. The breads were characterized by R5 competitive enzyme linked immunosorbent assay in order to quantify the residual gluten, and the differential efficacy in gluten degradation was assessed. In particular, two of them were classified as gluten-free (<20 ppm) and very low-gluten content (<100 ppm) breads, respectively, whereas the third monovarietal prototype retained a gluten content that was well above the safety threshold prescribed for direct consumption by CD patients. In order to investigate such a genotype-dependent efficiency of the detoxification method applied, an advanced proteomic characterization by high-resolution tandem mass spectrometry was performed. Notably, to the best of our knowledge, this is the first proteomic investigation which benefitted, for protein identification, from the full sequencing of the Triticum turgidum ssp. durum genome. The differences of the proteins' primary structures affecting their susceptibility to hydrolysis were investigated. As a confirmation of the previous immunoassay-based results, two out of the three breads made with the processed flours presented an exhaustive degradation of the epitopic sequences that are relevant for CD immune stimulatory activity. The list of the detected epitopes was analyzed and critically discussed in light of their susceptibility to the detoxification strategy applied. Finally, in-vitro experiments of human gastroduodenal digestion were carried out in order to assess, in-silico, the toxicity risk of the prototype breads under investigation for direct consumption by CD patients. This approach allowed us to confirm the total degradation of the epitopic sequences upon gastro-duodenal digestion.

Discovery based high resolution MS/MS analysis for selection of allergen markers in chocolate and broth powder matrices

Peptide marker identification is an important step in development of a mass spectrometry method for multiple allergen detection, since specificity, robustness and sensitivity of the overall analytical method will depend on the reliability of the proteotypic peptides. As part of the development of a multi-analyte reference method, discovery analysis of two incurred food matrices has been undertaken to select the most reliable peptide markers. Six allergenic ingredients (milk, egg, peanut, soybean, hazelnut, and almond) were incurred into either chocolate or broth powder matrix. Different conditions of protein extraction and purification were tested and the tryptic peptide pools were analysed by untargeted high resolution tandem mass spectrometry and the resulting fragmentation spectra were processed via a commercial software for sequence identification. The analysis performed on incurred foods provides both a prototype effective and straightforward sample preparation protocol and delivers reliable peptides to be included in a standardized selected reaction monitoring method.

Validation of a MS Based Proteomics Method for Milk and Egg Quantification in Cookies at the Lowest VITAL Levels: An Alternative to the Use of Precautionary Labeling

The prevalence of food allergy has increased over the last decades and consequently the food labeling policies have improved over the time in different countries to regulate allergen presence in foods. In particular, Reg 1169 in EU mandates the labelling of 14 allergens whenever intentionally added to foods, but the inadvertent contamination by allergens still remains an uncovered topic. In order to warn consumers on the risk of cross-contamination occurring in certain categories of foods, a precautionary allergen labelling system has been put in place by food industries on a voluntary basis. In order to reduce the overuse of precautionary allergen labelling (PAL), reference doses and action limits have been proposed by the Voluntary Incidental Trace Allergen Labelling VITAL project representing a guide in this jeopardizing scenario. Development of sensitive and reliable mass spectrometry methods are therefore of paramount importance in this regard to check the contamination levels in foods. In this paper we describe the development of a time-managed multiple reaction monitoring (MRM) method based on a triple quadrupole platform for milk and egg quantification in processed food. The method was in house validated and allowed to achieve levels of proteins lower than 0.2 mg of total milk and egg proteins, respectively, in cookies, challenging the doses recommended by VITAL. The method was finally applied to cookies labeled as milk and egg-free. This method could represent, in perspective, a promising tool to be implemented along the food chain to detect even tiny amounts of allergens contaminating food commodities.

Emerging Allergens in Goji Berry Superfruit: The Identification of New IgE Binding Proteins towards Allergic Patients' Sera

The goji berry (Lycium barbarum L.) (GB) is gaining increasing attention with high consumption worldwide due to its exceptional nutritional value and medicinal benefits displayed in humans. Beyond their beneficial properties, GBs contain renowned allergenic proteins, and therefore deserve inclusion among the allergenic foods capable of inducing allergic reactions in sensitive consumers. GB allergy has been frequently linked to the panallergen lipid transfer protein (LTP), especially across the population of the Mediterranean area. Methods: In this study, we investigated the protein profile of GBs focusing on the most reactive proteins against immunoglobulins E (IgE) of allergic patients' sera, as ascertained by immunoblot experiments. The protein spots displaying a clear reaction were excised, in-gel digested, and analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) followed by data searching against a restricted database for a reliable protein identification. Results: According to our data, three main spots were identified in GB extract as IgE binding proteins after immunoblot analysis. Some major proteins were identified and the three proteins that provided the highest reactivity were putatively attributed to vicilin and legumin proteins followed by a protein matching with 11S globulin belonging to the cupin superfamily. Finally, the whole GB protein extract was also submitted to bottom-up proteomics followed by a software-based database (DB) screening and a more exhaustive list of GB proteins was compiled.

Food allergens: Classification, molecular properties, characterization, and detection in food sources

Food allergy is a large and growing public health problem in many areas of the world. The prevalence of food allergy has increased in the last decades in a very significant way in many world regions, particularly in developed countries. In that respect, the research field of food allergy has experienced an extensive growth and very relevant progress has been made in recent years regarding the characterization of food allergens, the study of their immunological properties, and their detection in food sources. Furthermore, food labeling policies have also been improved decidedly in recent years. For that immense progress made, it is about time to review the latest progress in the field of food allergy. In this review, we intend to carry out an extensive and profound overview regarding the latest scientific advances and knowledge in the field of food allergen detection, characterization, and in the study of the effects of food processing on the physico-chemical properties of food allergens. The advances in food labeling policies, and methodologies for the characterization of food allergens are also thoroughly reviewed in the present overview.

Detection and Quantification of Allergens in Foods and Minimum Eliciting Doses in Food-Allergic Individuals (ThRAll)

Risk-based approaches to managing allergens in foods are being developed by the food industry and regulatory authorities to support food-allergic consumers to avoid ingestion of their problem food, especially in relation to the traces of unintended allergens. The application of such approaches requires access to good quality data from clinical studies to support identification of levels of allergens in foods that are generally safe for most food-allergic consumers as well as analytical tools that are able to quantify allergenic food protein. The ThRAll project aims to support the application of risk-based approaches to food-allergen management in two ways. First, a harmonized quantitative MS-based prototype reference method will be developed for the detection of multiple food allergens in standardized incurred food matrices. This will be undertaken for cow’s milk, hen’s egg, peanut, soybean, hazelnut, and almond incurred into two highly processed food matrices, chocolate and broth powder. This activity is complemented by a second objective to support the development and curation of data on oral food challenges, which are used to define thresholds and minimum eliciting doses. This will be achieved through the development of common protocols for collection and curation of data that will be applied to allergenic foods for which there are currently data gaps.

A Comprehensive Peptidomic Approach to Characterize the Protein Profile of Selected Durum Wheat Genotypes: Implication for Coeliac Disease and Wheat Allergy

The wheat varietal selection undertaken by breeders in recent decades has been tailored mainly to improve technological and productivity-related traits; however, the latter has resulted in a considerable impoverishment of the genetic diversity of wheat-based products available on the market. This pitfall has encouraged researchers to revalue the natural diversity of cultivated and non-cultivated wheat genotypes in light of their different toxic/immunogenic potential for celiac disease and wheat-allergic patients. In the present investigation, an advanced proteomic approach was designed for the global characterization of the protein profile of selected tetraploid wheat genotypes (Triticum turgidum). The approach combined proteins/peptides sequence information retrieved by specific enzymatic digestions (single and dual proteolytic enzymes) with protein digestibility information disclosed by means of in-vitro simulated human gastroduodenal digestion experiments. In both cases, the peptide pools were characterized by discovery analysis with liquid chromatography high-resolution tandem mass spectrometry, and specific amino acid sequences were identified via commercial software. The peptide list was screened for in silico toxicity/immunogenicity risk assessment, with the aid of various open-source bioinformatics tools for epitopes matching. Given the global information provided by the designed proteomic approach, the in silico risk assessment not only tackled toxicity implication for celiac disease patients, but also scouted for immunogenic sequences relevant for wheat allergic patients, achieving a comprehensive characterization of the protein profile of the selected genotypes. These latter were assessed to encrypt a variable number of toxic/immunogenic epitopes for celiac disease and wheat allergy, and as such they could represent convenient bases for breeding practices and for the development of new detoxification strategies.

Modulation of Milk Allergenicity by Baking Milk in Foods: A Proteomic Investigation

Cow's milk is considered the best wholesome supplement for children since it is highly enriched with micro and macro nutrients. Although the protein fraction is composed of more than 25 proteins, only a few of them are capable of triggering allergic reactions in sensitive consumers. The balance in protein composition plays an important role in the sensitization capacity of cow's milk, and its modification can increase the immunological response in allergic patients. In particular, the heating treatments in the presence of a food matrix have demonstrated a decrease in the milk allergenicity and this has also proved to play a pivotal role in developing tolerance towards milk. In this paper we investigated the effect of thermal treatment like baking of cow's milk proteins that were employed as ingredients in the preparation of muffins. A proteomic workflow was applied to the analysis of the protein bands highlighted along the SDS gel followed by western blot analyses with sera of milk allergic children in order to have deeper information on the impact of the heating on the epitopes and consequent IgE recognition. Our results show that incorporating milk in muffins might promote the formation of complex milk-food components and induce a modulation of the immunoreactivity towards milk allergens compared to milk baked in the oven at 180 °C for ten minutes. The interactions between milk proteins and food components during heating proved to play a role in the potential reduction of allergenicity as assessed by in vitro tests. This would help, in perspective, in designing strategies for improving milk tolerance in young patients affected from severe milk allergies.

Detection and Quantification of Allergens in Foods and Minimum Eliciting Doses in Food-Allergic Individuals (ThRAll)

Risk-based approaches to managing allergens in foods are being developed by the food industry and regulatory authorities to support food-allergic consumers to avoid ingestion of their problem food, especially in relation to the traces of unintended allergens. The application of such approaches requires access to good quality data from clinical studies to support identification of levels of allergens in foods that are generally safe for most food-allergic consumers as well as analytical tools that are able to quantify allergenic food protein. The ThRAll project aims to support the application of risk-based approaches to food-allergen management in two ways. First, a harmonized quantitative MS-based prototype reference method will be developed for the detection of multiple food allergens in standardized incurred food matrices. This will be undertaken for cow's milk, hen's egg, peanut, soybean, hazelnut, and almond incurred into two highly processed food matrices, chocolate and broth powder. This activity is complemented by a second objective to support the development and curation of data on oral food challenges, which are used to define thresholds and minimum eliciting doses. This will be achieved through the development of common protocols for collection and curation of data that will be applied to allergenic foods for which there are currently data gaps.

Scouting for Naturally Low-Toxicity Wheat Genotypes by a Multidisciplinary Approach

Over the last years, great efforts have been devoted to develop effective gluten detoxification strategies with a consequent detrimental alteration of the technological properties as well. Obtaining low-gluten products without affecting the rheological properties of wheat could still be considered a new challenge to face. In this investigation, we presented a comprehensive characterization of durum wheat genotypes aimed at identifying low gluten ones, which combine the potential lower toxicity/immunogenicity with conserved yield and rheological properties to encompass the perspective usability for bread or pasta making. A preliminary profiling of gluten proteins was accomplished by immunoassay-based quantification and liquid chromatography coupled to UV detection, focusing on the gliadin fraction as main responsible for immunoreactivity in celiac disease patients. In addition, data on grain protein content, grain yield per spike, dry gluten and gluten index were collected in order to provide complementary information about productivity-related traits and quali-quantitative characteristics related to wheat nutritional value and its technological properties. The whole pool of data was statistically evaluated driving to the selection of a preferred list of candidate low-toxicity genotypes that were subjected to in-vitro simulated gastroduodenal digestion and untargeted HR-MS/MS peptide identification. Finally, an in-silico risk assessment of potential toxicity for celiac disease patients was performed according to the most recent guidance provided by EFSA.

Heat and Pressure Treatments on Almond Protein Stability and Change in Immunoreactivity after Simulated Human Digestion

Almond is consumed worldwide and renowned as a valuable healthy food. Despite this, it is also a potent source of allergenic proteins that can trigger several mild to life-threatening immunoreactions. Food processing proved to alter biochemical characteristics of proteins, thus affecting the respective allergenicity. In this paper, we investigated the effect of autoclaving, preceded or not by a hydration step, on the biochemical and immunological properties of almond proteins. Any variation in the stability and immunoreactivity of almond proteins extracted from the treated materials were evaluated by total protein quantification, Enzyme Linked Immunosorbent Assay (ELISA), and protein profiling by electrophoresis-based separation (SDS-PAGE). The sole autoclaving applied was found to weakly affect almond protein stability, despite what was observed when hydration preceded autoclaving, which resulted in a loss of approximately 70% of total protein content compared to untreated samples, and a remarkable reduction of the final immunoreactivity. The final SDS-PAGE protein pattern recorded for hydrated and autoclaved almonds disclosed significant changes. In addition, the same samples were further submitted to human-simulated gastro-intestinal (GI) digestion to evaluate potential changes induced by these processing methods on allergen digestibility. Digestion products were identified by High Pressure Liquid Chromatography-High Resolution Tandem Mass Spectrometry (HPLC-HRMS/MS) analysis followed by software-based data mining, and complementary information was provided by analyzing the proteolytic fragments lower than 6 kDa in size. The autoclave-based treatment was found not to alter the allergen digestibility, whereas an increased susceptibility to proteolytic action of digestive enzymes was observed in almonds subjected to autoclaving of prehydrated almond kernels. Finally, the residual immunoreactivity of the GI-resistant peptides was in-silico investigated by bioinformatic tools. Results obtained confirm that by adopting both approaches, no epitopes associated with known allergens survived, thus demonstrating the potential effectiveness of these treatments to reduce almond allergenicity.

Insight into the gastro-duodenal digestion resistance of soybean proteins and potential implications for residual immunogenicity

Soy is an important component of the human diet thanks to its nutritional value and high protein content; however, it also represents a risk for allergenic consumers due to its potential to trigger adverse reactions in sensitized individuals. The putative correlation between immunoreactivity and resistance to the human gastrointestinal (GI) digestion has drawn attention to investigating soybean proteins digestibility. In this work, we provided further insights into this field by performing in vitro simulated GI digestion experiments directly on ground soybean seeds, to provide more realistic results obtained from the digestion of the whole food matrix. Soybean digestion products were analyzed by SDS-PAGE followed by untargeted HPLC-MS/MS analysis and the final data were software treated to enable protein/peptide identification. The latter allowed monitoring the proteolytic degradation of the main soybean proteins during the gastric and duodenal phases. In particular, β-conglycinin and trypsin inhibitors showed the highest resistance to the combined activity of GI enzymes, showing a partial degradation at the end of the duodenal phase as ascertained by the strong electrophoretic bands displayed at 50 kDa and 20 kDa, respectively. Glycinin subunits also presented, even if to a lower extent, resistance to the complete proteolytic degradation, as demonstrated by polypeptide fragments with molecular weight lower than 20 kDa displayed in the gel at the end of duodenal digestion. In addition, by bioinformatics analysis it was demonstrated that the GI resistant fragments of the allergenic proteins, β-conglycinin and glycinin, retained in their primary structure linear epitopes potentially able to trigger an immunoreaction when exposed to the intestinal mucosa. Moreover, such resistant peptides also presented a structural homology with epitope sequences recognized in other legume species, presenting a potential risk of adverse cross-reaction for a larger category of allergic consumers.

Streamlining the analytical workflow for multiplex MS/MS allergen detection in processed foods

Allergenic ingredients in pre-packaged foods are regulated by EU legislation mandating their inclusion on labels. In order to protect allergic consumers, sensitive analytical methods are required for detect allergen traces in different food products. As a follow-up to our previous investigations, an optimized, sensitive, label-free LC-MS/MS method for multiplex detection of five allergenic ingredients in a processed food matrix is proposed. A cookie base was chosen as a complex food matrix and home-made cookies incurred with whole egg, skimmed milk, soy flour, ground hazelnut and ground peanut were prepared at laboratory scale. In order to improve the analytical workflow both protein extraction and purification protocols were optimized and finally a sensitive streamlined SRM based analytical method for allergens detection in incurred cookies was devised. The effect of baking on the detection of selected markers was also investigated.

LC-tandem mass spectrometry as a screening tool for multiple detection of allergenic ingredients in complex foods

<!--[if gte mso 9]><xml> <o:OfficeDocumentSettings> <o:RelyOnVML /> <o:AllowPNG /> </o:OfficeDocumentSettings> </xml><![endif]--> <p class="Abstract"><span lang="EN-US">In the present investigation, an LC-MS/MS method for sensitive multiplex detection of five allergenic ingredients in a processed food matrix is presented. Cookie was chosen as complex food model and was incurred with egg, milk, soy, hazelnuts and peanuts before baking. Extraction, purification and pre-concentration protocols were applied to ground cookie basing on protocols described elsewhere. 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Orbitrap™ monostage MS versus hybrid linear ion trap MS: application to multi-allergen screening in wine

Food allergen research has made giant steps in the last years thanks to the features offered by the latest technology of mass analyzers placed on the market allowing multiplex sensitive detection of proteins. Potentials and features of two mass analyzers namely a linear ion trap capable of performing a data dependent or selected reaction monitoring analysis and an Orbitrap(TM) stand-alone MS enabling a broadband fragmentation without mass selection at highest mass resolving power are herein described and applied to the multiplex screening of allergens in a type of wine chosen as a reference matrix. Quantitative and confirmative capabilities of both platforms were assessed on the specific case study, the multiple detection of egg and milk -related proteins, typically employed in white wines as fining agents. Commercial bioinformatic tools used for a quick allergen identification will be also discussed.

Multi-allergen detection in food by micro high-performance liquid chromatography coupled to a dual cell linear ion trap mass spectrometry

There is a raising demand for sensitive and high throughput MS based methods for screening purposes especially tailored to the detection of allergen contaminants in different food commodities. A challenging issue is represented by complex food matrices where the antibody-based kits commercially available might encounter objective limitations consequently to epitope masking phenomena due to a multitude of interfering compounds arising from the matrix. The performance of a method duly optimized for the extraction and simultaneous detection of soy, egg and milk allergens in a cookie food matrix by microHPLC-ESI-MS/MS, is herein reported. Thanks to the innovative configuration and the versatility shown by the dual cell linear ion trap MS used, the most intense and reliable peptide markers were first identified by untargeted survey experiment, and subsequently employed to design an ad hoc multi-target SRM method, based on the most intense transitions recorded for each selected precursor peptide. A sample extraction and purification protocol was optimized also including an additional step based on sonication, which resulted in a considerable improvement in the detection of milk allergen peptides. Data Dependent™ Acquisition scheme allowed to fill out a tentative list of potential peptide markers, which were further filtered upon fulfilling specific requirements. A total of eleven peptides were monitored simultaneously for confirmation purposes of each allergenic contaminant and the two most sensitive peptide markers/protein were selected in order to retrieve quantitative information. Relevant LODs were found to range from 0.1μg/g for milk to 0.3μg/g for egg and 2μg/g for soy.

Multi-allergen quantification of fining-related egg and milk proteins in white wines by high-resolution mass spectrometry

RATIONALE

A method based on High-Resolution Mass Spectrometry was developed for the simultaneous determination of fining agents containing potentially allergenic milk (casein) and egg-white (lysozyme and ovalbumin) proteins, added to commercial white wines at sub-ppm levels. Selected tryptic peptides were used as quantitative markers. An evaluation of protein digestion yields was also performed by implementing the (15)N-valine-labelled analogues of the best peptide markers identified for αS1 -casein and ovalbumin.

METHODS

The method was based on the combination of ultrafiltration (UF) of protein-containing wines, tryptic digestion of the dialyzed wine extracts and liquid chromatography/high resolution mass spectrometry (LC/HRMS) analysis of tryptic digests. Peptides providing the most intense electrospray ionization (ESI)-MS response were chosen as quantitative markers of the proteins under investigation.

RESULTS

Six-point calibrations were performed by adding caseinate and egg-white powder in the concentration range between 0.25 and 10 µg/mL, to an allergen-free white wine. The following three peptide markers, LTEWTSSNVMEER, GGLEPINFQTAADQAR and ELINSWVESQTNGIIR, were highlighted as best markers for ovalbumin, while GTDVQAWIR and NTDGSTDYGILQINSR for lysozyme and YLGYLEQLLR, GPFPIIV and FFVAPFPEVFGK for caseinate. Limits of detection (LODs) ranged from 0.4 to 1.1 µg/mL.

CONCLUSIONS

The developed method is suited for assessing the contemporary presence of allergenic milk and egg proteins characterizing egg white and caseinate, fining agents typically employed for wine clarification. The LODs of the method enable the detection of sub-ppm concentrations of residual fining agents, that could represent a potential risk for allergic consumers.

Virus-poly(3,4-ethylenedioxythiophene) composite films for impedance-based biosensing

Composite films composed of poly(3,4-ethylenedioxythiophene), PEDOT, and the filamentous virus M13-K07 were prepared by electrooxidation of 3,4-ethylenedioxythiophene (EDOT) in aqueous solutions containing 8 nM of the virus at planar gold electrodes. These films were characterized using atomic force microscopy and scanning electron microscopy. The electrochemical impedance of virus-PEDOT films increases upon exposure to an antibody (p-Ab) that selectively binds to the M13 coat peptide. Exposure to p-Ab causes a shift in both real (Z(RE)) and imaginary (Z(IM)) impedance components across a broad range of frequencies from 50 Hz to 10 kHz. Within a narrower frequency range from 250 Hz to 5 kHz, the increase of the total impedance (Z(total)) with p-Ab concentration conforms to a Langmuir adsorption isotherm over the concentration range from from 6 to 66 nM, yielding a value for K(d) = 16.9 nM at 1000 Hz.