Properties of transglutaminase-induced myofibrillar/wheat gluten gels.

Gelation properties of myofibrillar protein (MP)/wheat gluten (WG) induced by glutamine transaminase (TGase) were studied. Results showed that the inclusion of transglutaminase increased the gel strength, water-holding capacity (WHC), and nonfreezable water (Wnf) of MP/WG mixture. Circular dichroism (CD) analysis showed that the ß-sheet and random coil content of the MP/WG treated with TGase addition increased by 12.1% and 3.7%, while the α-helix and ß-turn content decreased by 14.2% and 1.8%. Rheological measurements showed that TGase induced higher energy storage modulus value during the MP/WG gel heating-cooling cycle. the hydrogen bond and hydrophobic interaction content of the MP/WG gels increased by 80 and 120 ug/L, and the disulfide bond decreased by 200 ug/L, with TGase addition was increased from 0 to 120 U/g protein. Scanning electron microscope (SEM) showed that MP/WG gel with TGase had uniform and dense network structure. PRACTICAL APPLICATION: The properties of myofibrillar/wheat gluten gel induced by TGase crosslinking was studied. The gel structure and water holding capacity of MP/WG were improved by the cross-linking of TGase. The study of the gel properties of MP/WG induced by TGase crosslinking also can provide a theoretical basis for analyzing the effect of TGase on the application of gluten protein in complex meat emulsion system.

Effects of Hofmeister salt series on gluten network formation: Part I. Cation series.

Different cationic salts were used to investigate the effects of the Hofmeister salt series on gluten network formation. The effects of cationic salts on wheat flour dough mixing properties, the rheological and the chemical properties of the gluten extracted from the dough with different respective salts, were investigated. The specific influence of different cationic salts on the gluten structure formation during dough mixing, compared to the sodium ion, were determined. The effects of different cations on dough and gluten of different flours mostly followed the Hofmeister series (NH4(+), K(+), Na(+), Mg(2+) and Ca(2+)). The impacts of cations on gluten structure and dough rheology at levels tested were relatively small. Therefore, the replacement of sodium from a technological standpoint is possible, particularly by monovalent cations such as NH4(+), or K(+). However the levels of replacement need to take into account sensory attributes of the cationic salts.

Effects of Hofmeister salt series on gluten network formation: Part II. Anion series.

Different anion salts from the Hofmeister series were used to investigate their effects on gluten network formation. The effects of these anion salts on the mixing properties of the dough and the rheological and chemical properties of gluten samples extracted from the dough with these respective salts were compared. The aim of this work was to determine how different anion salts influence the formation of the gluten structure during dough mixing. It was found that the Hofmeister anion salts affected the gluten network formation by interacting directly with specific amino acid residues that resulted in changes in gluten protein composition, specifically the percentage of the unextractable polymeric protein fractions (%UPP). These changes consequently led to remarkable differences in the mixing profiles and microstructural features of the dough, small deformation rheological properties of the gluten and a strain hardening behaviour of both dough and gluten samples.

Pharmacological approaches in celiac disease.

Celiac disease is an autoimmune enteropathy triggered by the ingestion of gluten, characterized by immune responses toward gluten constituents and the autoantigen transglutaminase 2. The only current treatment available for celiac disease is a gluten-free diet, however there are a plethora of therapies in development for the treatment of celiac disease (e.g. vaccine), management of symptoms while consuming gluten (e.g. Necator americanus) or adjuvant therapies in conjunction with the gluten-free diet (e.g. larazotide acetate). Current approaches in development target barrier function, immune responses, detoxifying gluten or sequestering gluten. Developing therapies include those targeting environmental factors, such as the microbiota or proteases.

Dispersion in the presence of acetic acid or ammonia confers gliadin-like characteristics to the glutenin in wheat gluten.

Spray-dried gluten has unique properties and is commercially available in the food industry worldwide. In this study, we examined the viscoelastic properties of gluten powder prepared by dispersion in the presence of acetic acid or an ammonia solvent and then followed by lyophilization instead of a spray drying. Mixograph measurements showed that the acid- and ammonia-treated gluten powders had marked decreases in the time to peak dough resistance when compared with the control gluten powder. The integrals of the dough resistance and bandwidth for 3 min after peak dough resistance decreased in both treated gluten powders. Similar phenomena were observed when gliadin was supplemented to gluten powders. Basic and acidic conditions were applied to the acid- and ammonia-treated gluten powders, respectively, and the viscoelastic behaviors were found to depend on the pH in the gluten dispersion just before lyophilization. These behaviors suggest that gluten may assume a reversible change in viscoelasticity by a fluctuation in pH during gluten dispersion. SDS-PAGE showed that the extractable proteins substantially increased in some polymeric glutenins including the low molecular weight-glutenin subunit (LMW-GS) when the ammonia-treated gluten powder was extracted with 70% ethanol. In contrast, the extractable proteins markedly increased in many polymeric glutenins including the high molecular weight-glutenin subunit and/or the LMW-GS when the acid-treated gluten powder was extracted with 70% ethanol. It thus follows that the extractability of polymeric glutenin to ethanol increases similarly to gliadin when gluten is exposed to an acidic or a basic pH condition; therefore, glutenin adopts gliadin-like characteristics.

Influence of gallic acid and tannic acid on the mechanical and barrier properties of wheat gluten films.

Vital wheat gluten, a byproduct of wheat starch production, is a highly functional ingredient having a unique viscoelasticity that makes it ideal for the production of edible biodegradable films. However, its functional properties must be modified to ensure sufficient strength and elasticity, in addition to water vapor barrier properties. In this study, vital gluten was modified using tannic and gallic acid. It was found that the addition of tannic acid resulted in stiffer, more resistant, and less resilient and flexible films, having as well decreased water vapor permeability. Tannic acid containing films became reddish brown, whereas gallic acid addition did not have an influence on the film appearance. Films containing gallic acid became more elastic. Gallic acid was found to potentially act like a plasticizer. Scanning electron microscopy was used to investigate the ultrastructure of the produced films.

Modification of the wheat gluten network by Kraft lignin addition.

The effect of Kraft lignin (KL) on wheat gluten (WG) network formation during biomaterial processing was investigated. Gluten plasticized with glycerol was blended with a variable content of KL and processed into material by mixing and hot molding. The effect of KL on WG cross-linking was assessed by size-exclusion chromatography coupled with specific detection of KL by fluorescence. Whereas processing of WG usually results in cross-linking and solubility loss, KL addition promoted an increase of gluten protein solubility in sodium dodecyl sulfate buffers. The feature demonstrates that KL functional groups hinder WG aggregation. A radical scavenger activity of KL toward the thiyl radicals produced during gluten mixing is proposed. Mixing also promotes the association of KL with WG as evidenced by the coelution of KL and WG in size exclusion high-performance liquid chromatography. Finally, gluten aggregation and cross-linking can be obtained by immersion of the materials in a dioxane-water solution, thereby demonstrating the occurrence of stabilized radicals on WG material mixed with KL.

Disaggregation and reaggregation of gluten proteins by sodium chloride.

This study showed that gluten proteins were extracted with distilled water from dough prepared in the presence of NaCl. To elucidate the interrelationship of NaCl and gluten proteins in dough, the extracted proteins were characterized. These proteins were primarily found to be soluble gliadin monomers by N-terminal amino acid sequencing and analytical ultracentrifugation. Extracted proteins were aggregated by the addition of NaCl at concentrations of >10 mM. A decrease in beta-turn structures, which expose tryptophan residues to an aqueous environment in the presence of NaCl, was revealed by Fourier transform infrared analysis and scanning of fluorescence spectra. In addition, cross-linking experiments with disuccinimidyl tartrate showed that a large amount of protein was cross-linked in the dough only in the presence of NaCl. These results suggest that both interactions and distances between proteins were altered by the addition of NaCl.

Fermentation, purification, formulation, and pharmacological evaluation of a prolyl endopeptidase from Myxococcus xanthus: implications for Celiac Sprue therapy.

Celiac Sprue is a multi-factorial disease characterized by an inflammatory response to ingested wheat gluten and similar proteins in rye and barley. Proline-rich gluten peptides from wheat, rye, and barley are relatively resistant to gastrointestinal digestion, and therefore persist in the intestinal lumen to elicit immunopathology in genetically susceptible individuals. In this study, we characterize the in vitro gluten detoxifying properties of a therapeutically promising prolyl endopeptidase from Myxococcus xanthus (MX PEP), and describe the development of a prototypical enteric-coated capsule containing a pharmacologically useful dose of this enzyme. A high-cell density fed-batch fermentation process was developed for overproduction of recombinant MX PEP in E. coli, yielding 0.25-0.4 g/L purified protein. A simple, scalable purification and lyophilization procedure was established that yields >95% pure, highly active and stable enzyme as a dry powder. The dry powder was blended with excipients and encapsulated in a hard gelatin capsule. The resulting capsule was enteric coated using Eudragit L30-D55 polymer coat, which provided sufficient resistance to gastric conditions (> 1 h in 0.01 M HCl, pH 2 with pepsin) and rapid release under duodenal conditions (15-30 min release in pH 6.0 in the presence of trypsin and chymotrypsin). In conjunction with pancreatic enzymes, MX PEP breaks down whole gluten into a product mixture that is virtually indistinguishable from that generated by the Flavobacterium meningosepticum (FM) PEP as judged by chromatographic assays. Competitive studies involving selected immunogenic peptides mixed with whole gluten reveal that both PEPs have a wide range of substrate specificity. Our results support further in vitro and in vivo evaluation of the MX PEP capsule as an oral therapeutic agent for Celiac Sprue patients.

Transglutaminases: a meeting point for wheat allergy, celiac disease, and food safety.

Wheat is the staple cereal in many countries and its uses in manufactured foods are ever growing due to the technological qualities of gluten proteins. Transglutaminases (TG) are ubiquitous enzymes with many functions. They are able to transform proteins by deamidation and/or transamidation. This last reaction can cross-link proteins together. Intestinal tissue TG has been shown to play an important role in two kinds of immune reactions to wheat: celiac disease and wheat-dependent exercise-induced anaphylaxis. In addition, new epitopes have been suspected in cases of anaphylaxis to wheat isolates, a food ingredient consisting mainly of deamidated gluten proteins. As a microbial TG is included in many food technological processes, its safe use should be checked. This assessment must cover not only the safety of the TG itself but also that of the deamidated/cross-linked proteins generated by this enzyme. This article aims at discussing the possible consequences of using TG in food industry in the light of today knowledge about immune reactions to wheat.

Wheat gluten causes dendritic cell maturation and chemokine secretion.

Wheat gluten causes gut inflammation in genetically predisposed individuals. We tested the hypothesis that wheat gluten is not only a target of adaptive immunity, but also modulates the function of APC. Dendritic cells (DC) derived from the bone marrow of BALB/c mice were exposed to chymotrypsin-treated wheat gluten. This induced DC maturation as estimated by all surface markers tested (MHC class II, CD40, CD54, and CD86). The effect was dose dependent, and, at 100 microg/ml gluten matched that caused by 10 ng/ml LPS. A role of endotoxin contamination was ruled out by demonstrating the resistance of wheat gluten effects to LPS antagonist polymyxin B. DC from LPS nonresponder strain C3H/HeJ were affected by wheat gluten, but not by LPS. Proteinase K-digested wheat gluten was unable to stimulate DC maturation. Wheat gluten induced a unique secretion pattern of selected cytokines and chemokines in DC. Classic pro- or anti-inflammatory mediators were not produced, in contrast to LPS. Rather, chemokines MIP-2 and keratinocyte-derived cytokine were secreted in large amounts. We conclude that wheat gluten lowers the threshold for immune responses by causing maturation of APC, by attracting leukocytes and increasing their reactivity state. In the presence of an appropriate genetic predisposition, this is expected to increase the risk of adverse immune reactions to wheat gluten or to other Ags presented.