Gluten Assessment in Beers: Comparison by Different Commercial ELISA Kits and Evaluation of NIR Analysis as a Complementary Technique

Traditionally, beers are made with gluten-containing cereals. It is crucial to have rapid analytical methodologies that allow gluten content control of the beers for celiac consumers. We assess the content of gluten in 65 conventional and 41 gluten-free labeled beers commercialized in Europe and compare the results in a subgroup of 71 beers with three ELISA kits. This research allows gathering information on the potential complementary utility of NIR analysis applied to gluten analysis of gluten-free beers in terms of time saving. Results obtained with the ELISA technique identified competitive R5 to be the most sensitive in detecting the prolamins, by eliciting a higher number of beers containing gluten above 20 mg/kg. The gluten content in conventional beers tested increased with the presence of wheat as raw material and with the use of ale-type yeasts. By using competitive R5, 3 out of the 41 gluten-free labeled beers appeared to contain gluten above 20 mg/kg, and conversely, 15 out of 65 of the conventional beers showed a gluten content below this threshold. According to our approaches, NIR did not achieve a suitable correlation with ELISA results, neither for gluten quantification nor for discrimination, and therefore, it cannot be proposed as a complementary technique.

Rapid, Effective, and Versatile Extraction of Gluten in Food with Application on Different Immunological Methods

One of the main concerns in gluten analysis is to achieve efficient extraction of gluten proteins. Conventional ethanol-based extraction solutions are inefficient and, because of this, it is necessary to use reducing agents or acids for proper solubilization. The extraction recommended by CODEX Standard 118-1979 (revised 2008) utilizes Cocktail solution (patent WO 02/092633 A1). However, it is harmful with a disgusting odor and is not compatible with some immunological techniques. Here, the versatility and extraction capacity of a new Universal Gluten Extraction Solution (UGES) (patent ES 2 392 412 A1) were evaluated using different methodological conditions, food matrices, and various immunological methods. UGES includes safer compounds for both the user and the environment, and it displayed similar extraction efficiency to that of the extraction method recommended for sandwich enzyme-linked immunosorbent assay (ELISA). The extraction time was significantly reduced from 100 to 40 min, depending on the type of the sample. Furthermore, unlike the currently used solution, UGES is compatible with competitive ELISA.

Comparative Characterization of Gluten and Hydrolyzed Wheat Proteins

Hydrolyzed wheat proteins (HWPs) are widely used as functional ingredients in foods and cosmetics, because of their emulsifying and foaming properties. However, in individuals suffering from celiac disease or wheat allergy, HWPs may have a modified immunoreactivity compared to native gluten due to changes in molecular structures. Although a variety of HWPs are commercially available, there are no in-depth comparative studies that characterize the relative molecular mass (Mr) distribution, solubility, and hydrophilicity/hydrophobicity of HWPs compared to native gluten. Therefore, we aimed to fill this gap by studying the above characteristics of different commercial HWP and gluten samples. Up to 100% of the peptides/proteins in the HWP were soluble in aqueous solution, compared to about 3% in native gluten. Analysis of the Mr distribution indicated that HWPs contained high percentages of low-molecular-weight peptides/proteins and also deamidated glutamine residues. We also found considerable differences between the seven HWPs studied, so that each HWP needs to be studied in detail to help explain its potential immunoreactivity.

Detection of gluten in duplicate portions to determine gluten intake of coeliac disease patients on a gluten-free diet

This study determined the gluten content of foods and meals consumed by coeliac disease (CD) patients who adhere to a gluten-free diet, and to estimate the total daily intake of gluten of these patients. CD patients fulfilling defined inclusion criteria were preselected and approached for participation in the study. Duplicate portions (DP) of foods and mixed dishes were collected from the CD patients for evaluating complete daily food intake during two individual days. Also, for these days, written food records were completed by the participants. From each DP, a laboratory sample was prepared and analysed for its gluten concentration and total daily gluten intake was calculated. Each individual’s total daily intakes of energy and macronutrients were calculated using the Dutch food composition database. In total, twenty-seven CD patients participated, seven males and twenty females, aged between 21 and 64 years. In thirty-two (6 %) of 499 food samples collected in total, more than 3 mg/kg gluten was present. In four of these thirty-two samples, the gluten concentration was above the European legal limit of 20 mg/kg and three of the four samples had a gluten-free label. The maximal gluten intake was 3·3 mg gluten/d. The gluten tolerance for sensitive CD patients (>0·75 mg/d) was exceeded on at least six out of fifty-four study days. To also protect these sensitive CD patients, legal thresholds should be re-evaluated and the detection limit of analytical methods for gluten analysis lowered.

Gluten Analysis in Processed Foodstuffs by a Multi-Allergens and Grain-Specific UHPLC-MS/MS Method: One Method to Detect Them All

Background: Celiac disease, a complex, long-term autoimmune disorder and gluten intolerance, is estimated to affect from 1 to 5% of the world’s population. Objective: As a consequence, to protect gluten-sensitive consumers, the development of reliable analytical methods allowing the detection of gluten in various food products is needed. Methods: Currently, ELISA is probably the most widespread used methodology. The method based on the R5 antibody has received type I status in Codex Alimentarius. However, the ELISA method suffers from some limitations, especially concerning quantification of nonwheat gluten. As a consequence, the development of another complementary methodology such as LC–tandem MS (MS/MS) is considered to be essential. Furthermore, this method could also be used for the simultaneous detection of gluten with other allergens, which will constitute a great additional benefit for producers of “free-from” food products and/or having a management policy integrated for several allergies and/or intolerances. Results: A multi-allergen and grain-specific ultra-HPLC coupled to MS/MS method allowing the identification and the discrimination of gluten from seven cereals, simultaneously with the detection and identification of 10 allergens in only one analysis, is thus described here. Conclusions: This method can be used for the analysis of a broad range of foodstuff matrices containing wheat and/or its derivatives, including cereals, flours, heat-treated and foodstuffs, but also more complex samples having undergone fermentation processes (such as beers).