Gluten Levels Research Articles

Assessment of the gluten content in gluten-free labeled foods: comparison of two gluten detection methods

This study was designed to compare the effectiveness of the R5-ELISA and immunochromatographic assays in detecting gluten in foods labeled gluten-free and to determine if the immunochromatographic method is a sensitive and reliable method for detecting gluten at safe levels for celiac patients. We analyzed seventy different commercially foods available in Brazil, labeled “gluten-free”. Gluten was extracted by ethanol precipitation and, subsequently, analyzed using a commercial immunochromatographic test and ELISA kit, both based in a monoclonal antibody. The analysis of sensitivity and specificity was made using the kappa coefficient. More than a quarter of the samples (28.6%) analyzed by ELISA contained levels of gluten greater than 5 mg/kg. Almost half of these (12.9%) exhibited levels that exceeded 20 mg/kg, the maximum gluten level recommended by the Codex Alimentarius for a naturally gluten-free product. We found 27.1% of the samples tested positive in the immunochromatographic test. There was no statistically significant difference between the results of the ELISA (detection value ≥ 5 mg/kg) and the immunochromatographic test. Comparing the ELISA (≥ 5 mg/kg) and immunochromatographic test, we obtained 90% sensitivity and 98% specificity (Kappa of 0.89). We found gluten in a high proportion of the samples tested using both methods. In this study we also demonstrate that the immunochromatographic method is nearly as sensitive as the ELISA in detecting gluten levels and thus may serve as an inexpensive and rapid alternative to the R5-ELISA screening test.

Gluten in Rice Flour and Baked Rice Products by G12 Sandwich ELISA: First Action 2014.03.

The Protein and Enzymes Technical Committee of American Association of Cereal Chemists initiated a collaborative study to confirm whether the G12 antibody-based sandwich ELISA test kit is able to detect gluten in the lower mg/kg (ppm) level. Twenty laboratories investigated 24 heat-treated and non-heat-treated blind-coded samples with incurred gluten levels up to 100 mg/kg. The method has been validated for testing foods to conform to the defined Codex thresholds for gluten in gluten-free products at less than 20 mg gluten/kg. The collaborative study showed that low levels of gluten could be detected by G12 Sandwich ELISA with reproducibility RSDR of 32% and repeatability RSDr of 16%. Incurred samples showed a recovery between 62 and 135%. It is recommended that the method be accepted by AOAC as Official First Action.

Evaluation of qualitative and quantitative immunoassays to detect barley contamination in gluten-free beer with confirmation using LC/MS/MS.

To meet the need for the detection and quantitation of barley gluten in beer, qualitative screening and quantitative immunoassays based on the monoclonal antigluten antibody 401/21 (Skerritt) were validated in a single laboratory. Sample replicates were tested at each stage of beer production using multiple yeast strains and methods of end-stage protein removal. Quantitation was performed using barley-specific standards based on barley flour extracts. Immunoassay results were confirmed using LC/MS/MS for barley-specific peptides. The LOD for the qualitative screening test was 5 mg/L barley gluten. Recovery for the barley-spiked worts ranged from 81 to 128% in the quantitative ELISA assay; the LOD was <1 mg/L, and the LOQ was 5 mg/L. Both screening and confirmation methods were found to be fit for the purposes of detection of low levels of barley gluten in beer.

Gluten Contamination in Foods Labeled as “Gluten Free” in the United States

Gluten is the main storage protein in grains and consists of gliadin and glutenin occurring in the same ratio. Persons suffering from intolerances, including celiac disease, must avoid foods containing gluten or products containing wheat, barley, and rye. Accordingly, gluten detection is of high interest for the food safety of celiac patients. This study was designed to determine the concentrations of gluten in foods labeled "gluten free" available in the United States. Seventy-eight samples labeled gluten free were collected and analyzed using a gliadin competitive enzyme-linked immunosorbent assay. The gluten content was calculated based on the assumption of the same ratio between gliadin and glutenin. Forty-eight (61.5%) of the 78 samples contained less than the limit of quantification of 10 mg/kg for gluten. In addition, 14 (17.9%) of the 78 samples labeled gluten free contained less gluten than the guidelines established by the Codex Alimentarius for gluten-free labeling (20 mg/kg). However, 16 samples (20.5%) did contain gluten levels of ≥20 mg/kg, ranging from 20.3 to 60.3 mg/kg. In particular, five of eight breakfast cereal samples showed gluten contents higher than 20 mg/kg. These results may be of concern, as gluten sensitivity is known to vary among celiac disease patients.

The role of gluten proteins in production and quality of a yeast leavened sugar and fat rich wheat based food model system

Little if any literature is available on the functionality of gluten proteins in yeast leavened developed dough systems containing high sugar and fat levels. We here studied whether and to what extent gluten proteins impact the different phases of the production of such a system (which contains about 35 parts invert syrup and 70 parts margarine per 100 parts flour) and how these proteins affect its quality. In a first approach, we used model systems based on gluten–starch blends as this allowed specifically altering the gluten levels without altering the gluten quality and/or levels of other wheat flour components. In a second approach flour was heat treated upfront to alter its gluten proteins. Despite the large amounts of sugars and fat, the presence of a developed gluten network in these systems allowed dough pieces to retain gas during fermentation. Also, dough pieces with a developed gluten network could expand faster during subsequent baking than dough pieces without a developed gluten network (i.e. ca. 3.6 vs. 1.9cm/min, respectively). Remarkably, at a given moment during baking (i.e. between 65 and 105sec of baking), dough pieces started to shrink in all directions. This was related to the (elastic) protein network present in the system. However, the time at which shrinking occurred was influenced by factors other than the gluten network. Besides the level, the quality of the gluten fraction determined gluten development during mixing of dough systems containing high levels of sugars and fat, and thus, the spread behavior during fermentation and baking and the final product's dimensions.

Estimated Levels of Gluten Incidentally Present in a Canadian Gluten-Free Diet

Avoiding exposure to gluten is currently the only effective treatment for celiac disease. However, the evidence suggests that for most affected individuals, exposure to less than 10 mg/day is unlikely to cause histological changes to the intestinal mucosa. The daily diet of people with celiac disease does not rely solely on gluten-free pre-packaged foods, but also on naturally gluten-free grains (e.g., rice, buckwheat, ...) and foods with grain-derived ingredients (i.e., flour and starches) used for cooking and baking at home. The objective of this study was to estimate the level of incidental gluten potentially present in gluten-free diets from a Canadian perspective. We have conducted gluten exposure estimations from grain-containing foods and foods with grain-derived ingredients, taking into consideration the various rates of food consumption by different sex and age groups. These estimates have concluded that if gluten was present at levels not exceeding 20 ppm, exposure to gluten would remain below 10 mg per day for all age groups studied. However, in reality the level of gluten found in naturally gluten-free ingredients is not static and there may be some concerns related to the flours made from naturally gluten-free cereal grains. It was found that those containing a higher level of fiber and that are frequently used to prepare daily foods by individuals with celiac disease could be a concern. For this category of products, only the flours and starches labelled “gluten-free” should be used for home-made preparations.

Studies on suitability of wheat flour blends with sweet potato, colocasia and water chestnut flours for noodle making

Blends of refined wheat flour (RWF) with colocasia (CF), sweet potato (SPF) and water chestnut (WCF) flours respectively at replacement level of 25 g/100 g were assessed for their suitability for noodles making. All the native flours as well as their blends with RWF exhibited restricted swelling behavior. Incorporation of SPF or CF into RWF decreased the peak viscosity of flour blends. Noodles prepared from respective flour blends of SPF and CF with RWF showed lower cooking time, higher cooked weight, higher water uptake and higher gruel solid loss in comparison to control sample (RWF noodles). Among blend flours noodles, RWF and SPF blend noodles were rated superior for their organoleptic/eating characteristics of slipperiness, firmness, appearance but undesirable high value of tooth packing. Noodle with acceptable quality characteristics and decreased level of gluten, which may prove beneficial for celiac persons, can be developed using RWF blends with non-conventional flours like colocasia, sweet potato and water chestnut.

Effects of Sorghum Flour Addition on Chemical and Rheological Properties of Hard White Winter Wheat

This study was carried out to investigate the chemical and rheological properties of different blends prepared using hard white winter wheat (HWWW; Triticum aestivum Desf.) and whole or decorticated sorghum (Sorghum bicolor). Whole and decorticated sorghum were used to replace 5, 10, 15 and 20% of wheat flour. Wheat samples had higher protein, moisture and calcium values and lower fat, ash, carbohydrates, iron and phosphorous values compared to whole and decorticated sorghum flours. Decortication of sorghum grains decreased moisture, ash, fat, crude protein, iron and phosphorous content, but increased carbohydrate content. Farinogram properties such as dough water absorption, development time and stability and Farinograph quality number decreased as the amount of substituted sorghum increased; whereas mixing tolerance index increased. Moreover, at fixed gluten levels, as sorghum flour increased in the blend, wet gluten, dry gluten and gluten index decreased. Increasing sorghum in the blend also decreased energy, resistance to extension and extensibility of the dough, but contributed to an increase in the ratio of resistance to extensibility. Furthermore, as fermentation time increased, energy, resistance to extension and the ratio number of energy to extension increased, whereas extensibility decreased.

Spanish Ancient Wheats: A Genetic Resource for Wheat Quality Breeding

Wheat (Triticum sp.) is one of the most important food crops worldwide. Di-, tetra- and hexaploid species are available, which along with the different subspecies of this genus have been used for food and feed. However, the genetic diversity of this crop has been seriously compromised, and only two main species; the durum and bread wheat, currently exist. The germplasm materials that were used in the past in Spain, have been regarded as ancient wheats, thus forming a group of neglected or underutilized crops that could be an interesting reservoir of variation for modern wheat breeding. In the last decade, our group has been evaluating and characterizing for the morphological and quality traits some of these Spanish ancient wheats. In these materials, using the SDS-PAGE technique and DNA sequencing, we detected an important variability for seed storage proteins, starch synthases and puroindolines, which are related with three important quality characteristics of wheat: gluten levels, starch levels and hardness, respectively. These novel variants could be used with the dual goal of genetic improvement and enriching the gene pool of these components in modern wheat.

Lipid composition and metabolism of European sea bass (Dicentrarchus labrax L.) fed diets containing wheat gluten and legume meals as substitutes for fish meal

The role of dietary protein source on growth performance and lipid metabolism in European sea bass (Dicentrarchus labrax) was investigated, by the evaluation of fat content in different tissues, plasma metabolites, liver lipogenic activity and fatty acid composition of dorsal muscle tissue.Five isonitrogenous (490gkg−1 crude protein dry-matter basis) and isolipidic (170gkg−1 lipid dry-matter basis) diets with graded levels of wheat gluten, soybean and pea meal in substitution of fish meal were evaluated in European sea bass (initial body weight 23.9±0.1) for 96days. There was a significant difference (p<0.05) in dorsal muscle and liver lipid contents. Plasma glucose and cholesterol levels decreased significantly (p<0.05) as diet included soybean and wheat gluten meal (p<0.05). The composition of fatty acids in muscle triacylglycerols and phospholipids was affected by vegetable sources as n−6 PUFA percentage was significantly increased and n−3 PUFA percentage was significantly decreased (p<0.05), without modifying EPA/DHA ratio, when wheat gluten and pea meal were included in the diet. The results confirm that the quality and quantity of vegetable protein source could affect lipid metabolism and lipid content in the dorsal muscle of the European sea bass and suggest the possibility of manipulation of the diet for commercial purpose.

Clinical nutrition update 2012.

Clinical nutrition update 2012.

Significant differences in coeliac immunotoxicity of barley varieties

The only treatment available for coeliac disease (CD) is a strict diet in which the intake of wheat, barley, rye, or oats is avoided. Barley is a major cereal crop, grown mainly for its use in brewing, and it has high nutritional value. The identification of varieties with a reduced toxicity profile may contribute to improve the diet, the quality of life and health of CD patients. Searching for harmless barleys, we investigated accessions of malting and wild barley, used for developing new cultivated cereals. The CD toxicity profile of barleys was screened using G12 antibody and cell proliferation and IFN-γ release from peripheral blood mononuclear cells and intestinal biopsies from CD patients. We found a direct correlation between the reactivity with G12 and the immunogenicity of the different barleys. The malting barleys were less immunogenic, with reduced levels of toxic gluten, and were possibly less harmful to CD patients. Our findings could raise the prospect of breeding barley species with low levels of harmful gluten, and the attractive goal of developing nontoxic barley cultivars, always taking into account the Codex standard for foods for special dietary use for persons intolerant to gluten.

Gluten-Free Diet: Imprudent Dietary Advice for the General Population?

As of April 20, 2012, Amazon.com listed 4,765entriesforthetopic“gluten-free.”AGooglesearchatthesametime for “gluten-free diet” produced more than 4.2 millionresults. The number-one reason consumers cite for buyinggluten-freeproductsisthattheyareperceivedtobehealthierthan their gluten-containing counterparts.

Malt hydrolysates for gluten-free applications: Autolytic and proline endopeptidase assisted removal of prolamins from wheat, barley and rye

Cereal based products intended for gluten sensitive individuals, particularly to celiac disease patients, tend to have poor organoleptic qualities and they contain low levels of healthy whole grain compounds. Adding whole grain ingredients, such as malt hydrolysates, could compensate these defects provided that the ingredients are adequately free from toxic prolamin epitopes. Here we demonstrate that the level of toxic prolamin epitopes in the malt autolysates (wheat, barley, rye) were substantially lower than in the native malts but too high to allow “very low in gluten” labelling. To further eliminate the residual levels of toxic prolamin epitopes, a proline-specific endoprotease from Aspergillus niger was added to the malt autolysates. In the resulting malt hydrolysates (of wheat and rye but not barley), the prolamins were indeed greatly reduced and were below the very low gluten limit of 100 mg/kg. Malt hydrolysates with adequately low gluten levels may potentially be used as novel ingredients within gluten-free foods.

Wheat gluten and potato protein concentrate — Promising protein sources for organic farming of rainbow trout (Oncorhynchus mykiss)

In contrast to potato and other plant proteins, wheat gluten does not require complex and costly purification and may thus be utilized in aquaculture diets according to aquaculture guideline EC 710/2009. Therefore, a feeding trial was conducted to evaluate the effect of various combinations of wheat gluten (WG) and potato protein concentrate (PPC) in nutrition of rainbow trout (Oncorhynchus mykiss). Seven isonitrogenous (459±6g CP kg−1) and isoenergetic (21.4±0.1MJkg−1) diets were formulated to contain varying levels of wheat gluten and potato protein concentrate (6/27; 9/24; 11/21; 14/19; 17/16; 19/13 as proportion of WG/PPC in % of the diet) at constant fishmeal replacement level of 56% on protein level and one fish meal diet served as control. Experimental diets were fed over a period of 56days to triplicate experimental groups until apparent satiation.Growth performance showed no significant differences between all feeding groups at the end of the experimental period. No influences on health and nutritional status were documented between the treatments in the body composition and blood parameter. The wheat gluten and PPC as fish meal replacement in organic diets for rainbow trout revealed positive and equal results for use in the inclusion level of the presented trial.

Effect of Gluten Powder on the Quality of Fresh Spaghetti Made with Farina

The objective of this study was to improve the quality of fresh spaghetti made from ordinary wheat flour using gluten powder at different levels (0.0, 0.5, 1.5 and 3.0%, w/w, flour basis). The spaghetti dough was evaluated by a Brabender Farinograph. The results indicated that with increasing the gluten level, peak, stability time and consistency of the dough increased. The results of creep test (carried out using a Texture Analyser) showed that with increasing the gluten content, elasticity of the dough increased while its viscosity decreased. Increasing the gluten level reduced the cooking loss and increased the water absorption of the samples cooked in distilled or salted water (2% NaCl). The hardness and the color of the uncooked and cooked spaghettis improved with increasing the gluten content. The sample containing 3% gluten powder cooked in salted water received the highest score for its sensory attributes.

Enzyme‐Linked Immunosorbent Assay Gliadin Assessment in Processed Food Products Available for Persons With Celiac Disease

Inappropriate food labeling and unwillingness of food companies to officially register their own gluten-free products in the Greek National Food Intolerance Database (NFID) result in a limited range of processed food products available for persons with celiac disease (CDP). The objective of the study was to evaluate the feasibility of developing a gluten-free food product database based on the assessment of the gluten content in processed foods available for CDP. Gluten was assessed in 41 processed food products available for CDP. Group A consisted of 26 products for CDP included in the NFID, and group B contained 15 food products for CDP not registered in the NFID but listed in the safe lists of the local Celiac Association (CA). High-sensitivity ω-gliadin enzyme-linked immunosorbent assay (ELISA) was used for analysis. Gluten was lower than 20 ppm in 37 of 41 analyzed products (90.2%): in 24 of 26 (92.3%) products in group A and in 13 of 15 (86.7%) products in group B (P = .61). No significant difference was found between the 2 groups regarding gluten content. No product in either group contained gluten in excess of 100 ppm. Most of the analyzed products included in the Greek NFID or listed in the lists of the local CA, even those not officially labeled "gluten free," can be safely consumed by CDP. The use of commercially available ω-gliadin ELISA is able to identify those products that contain inappropriate levels of gluten, making feasible it to develop an integrated gluten-free processed food database.

EFFECTS OF GLUTEN POWDER ON THE QUALITY OF WHEAT FLOUR SPAGHETTI COOKED IN DISTILLED OR SALTED WATER

ABSTRACTTo improve the quality of spaghetti produced from low protein wheat flour, gluten powder was added at 0.5, 1.5 and 3% (w/w). These samples were cooked in distilled or salted water (2% NaCl). The results showed that addition of gluten reduced cooking loss and increased water absorption. These parameters increased further when salt was added to the cooking water. With increasing the gluten powder, the color of the dried and cooked samples became darker and more yellow. Addition of salt reduced the lightness, while it increased the yellowness of the samples. Increasing the gluten level decreased the adhesiveness, while it increased the cohesiveness, elasticity and breaking strength of the cooked samples. A positive correlation between adhesiveness and cooking loss was found (R2 = 0.94) while other textural parameters had negative correlation with cooking loss (R2 = 0.99). According to the taste panel, a sample containing 3% gluten powder cooked in salted water was recognized as the best.PRACTICAL APPLICATIONSThis study shows an easy and applicable method of improving the quality of pasta made from low protein wheat flour using gluten powder. Different aspects of pasta quality including cooking, textural and sensory attributes were considered in this study. Hence, the findings may be useful for pasta producers in some parts of the world where ordinary wheat flour is the most available type of flour for pasta production.

Effect of incorporation of corn byproducts on quality of baked and extruded products from wheat flour and semolina

The effect of blending level (0, 5, 10, 15 and 20%) of corn bran, defatted germ and gluten with wheat flour on the physico-chemical properties (protein, crude fiber, phosphorus, iron and calcium), baking properties of bread, muffins and cookies, and extrusion properties of noodles and extruded snacks prepared from semolina were examined. Blending of wheat flour and corn byproducts significantly increased the protein, crude fiber, phosphorus, iron and calcium contents. Breads from gluten blends had higher loaf volume as compared to bran and germ breads. Among corn byproducts, gluten cookies were rated superior with respect to top grain. Muffins from germ blends and gluten blends had higher acceptability scores than the bran muffins. Blending of corn bran, defatted germ and gluten at 5 and 10% with wheat flour resulted in satisfactory bread, cookie, and muffin score. Quality of noodles was significantly influenced by addition of corn byproducts and their levels. Corn byproducts blending had significant influence on cooking time, however, gruel solid loss affected non-significantly in case of noodles. Expansion ratio and density of extruded snacks was affected non significantly by blending source and blending level. However, significant effect was observed on amperage, pressure, yield and overall acceptability of extruded snacks. Acceptable extruded products (noodles and extruded snacks) could be produced by blending corn byproducts with semolina upto 10% level.

Gluten Contamination of Grains, Seeds, and Flours in the United States: A Pilot Study

Under the Food Allergen and Consumer Protection Act, the Food and Drug Administration (FDA) must issue a rule for the voluntary labeling of food as gluten-free. In the proposed rule, many single-ingredient foods, such as millet, are considered inherently free of gluten. Inherently gluten-free grains will be considered misbranded if they carry a gluten-free label and do not also state that all foods of the same type are gluten-free (eg, “all millet is gluten free”). Twenty-two inherently gluten-free grains, seeds, and flours not labeled gluten-free were purchased in June 2009 and sent unopened to a company who specializes in gluten analysis. All samples were homogenized and tested in duplicate using the Ridascreen Gliadin sandwich R5 enzyme-linked immunosorbent assay with cocktail extraction. Thirteen of 22 (59%) samples contained less than the limit of quantification of 5 parts per million (ppm) for gluten. Nine of 22 (41%) samples contained more than the limit of quantification, with mean gluten levels ranging from 8.5 to 2,925.0 ppm. Seven of 22 samples (32%) contained mean gluten levels ≥20 ppm and would not be considered gluten-free under the proposed FDA rule for gluten-free labeling. Gluten contamination of inherently gluten-free grains, seeds, and flours not labeled gluten-free is a legitimate concern. The FDA may want to modify their proposed rule for labeling of food as gluten-free, removing the requirement that gluten-free manufacturers of inherently gluten-free grains, seeds, and flours must state on product labels that all foods of that type are gluten-free.