Y. Popineau

Improvement of functional properties of β-lactoglobulin glycated through the Maillard reaction is related to the nature of the sugar

The improvement of functional properties of proteins available in large quantity using non-toxic chemical modifications is of a great interest for the food industry. In this study, the Maillard reaction was used to improve the functional properties (solubility, heat stability, emulsifying and foaming properties) of β-lactoglobulin (BLG) glycated with several sugars (arabinose, galactose, glucose, lactose, rhamnose or ribose). Protein samples were heated in the presence or absence (heated control) of different sugars for three days at 60°C. Subsequent glycation induced a modification of the solubility profile shifting minimum solubility towards more acidic pH. Glycated proteins exhibited a better thermal stability when heated at pH 5 as compared to native or heated control. Glycation of BLG with arabinose or ribose (the most reactive sugars) improved its emulsifying properties. Foaming properties were better when BLG was glycated with glucose or galactose (moderately reactive sugars). These results suggest that the nature of the sugar is an essential factor for improving the functional properties of glycated proteins by processes of Maillard reaction.

Wheat glutenin subunits and dough elasticity: findings of the EUROWHEAT project

Detailed studies of wheat glutenin subunits have provided novel details of their molecular structures and interactions which allow the development of a model to explain their role in determining the visco-elastic properties of gluten and dough. The construction and analysis of near-isogenic and transgenic lines expressing novel subunit combinations or increased amounts of specific subunits allows differences in gluten properties to be related to the structures and properties of individual subunits, with potential benefits for the production of cultivars with improved properties for food processing or novel end users

Biochemical Analysis and Rheological Properties of Gluten Modified by Transglutaminase

ABSTRACT A transglutaminase from Streptoverticillium sp. was used to create new covalent intermolecular cross-links between proteins in gluten. This modification induced drastic changes in its physicochemical properties as well as in its rheological behavior. To understand these changes, we characterized the gluten extractability in acetic acid and identified the proteins of supernatant and pellet by immunoblotting using antibodies specific for each prolamin class. The proportion of soluble proteins decreased drastically after transglutaminase treatment due to the formation of large insoluble polymers as shown by SDS-PAGE. Among the constitutive proteins of gluten, the high molecular weight glutenin subunits were the most affected in the transglutaminase reaction. The rheological behavior of gluten after 18 hr of incubation with transglutaminase was studied in shear by dynamic measurements over 10-3 – 101 Hz frequency range and by creep and recovery tests. The behavior of treated glutens remained that of ...

Identification of IgE-binding epitopes on gliadins for patients with food allergy to wheat

Background:  Food allergy to wheat induces different symptoms as atopic eczema/dermatitis syndrome (AEDS), urticaria and more severe reactions as wheat‐dependent exercise‐induced anaphylaxis (WDEIA). Different gliadin classes are involved in this allergy but IgE‐binding epitopes are known only on ω5‐gliadins and for WDEIA cases.

Gliadin nanoparticles for the controlled release of all-trans-retinoic acid

Abstract The general objective of this work was to study the feasibility of preparing small-sized carriers from vegetal macromolecules. For this purpose, gliadin (a vegetal protein fraction from wheat gluten) nanoparticles were chosen as drug carriers for all-trans-retinoic acid (RA). The systems were prepared by a desolvation method for macro-molecules, which enabled us to obtain gliadin nanoparticles of about 500 nm, with a yield close to 90% of the initial protein. All experiments were performed using environmentally acceptable solvents such as ethanol and water. Moreover, due to the low solubility of this protein in water and to its high hydrophobicity, nanoparticles from gliadin do not need any further chemical or physical treatment to harden them. Gliadin nanoparticles were quite stable over 4 days in phosphate-buffered saline (PBS), but were degraded rapidly over 3 h when incubated in PBS solution containing trypsin. However, chemical cross-linkage of nanoparticles with glutaraldehyde significantly increased their stability. Under our experimental conditions, the payload limit was 76.4 μg RA/mg nanoparticles (for an RA/initial protein ratio of 90 μg/mg), which corresponded to a RA entrapment efficiency of about 75% of added drug. Nevertheless, the entrapment efficiency was high (between 97 and 85%) for RA/initial protein ratios up to 90 μg/mg. Finally, the in vitro release profiles of RA-loaded gliadin nanoparticles showed a biphasic pattern. An initial burst effect (in which about 20% RA was released) followed by zero-order diffusion (release rate 0.065 mg RA/h) were observed.

Food allergy to wheat: identification of immunogloglin E and immunoglobulin G-binding proteins with sequential extracts and purified proteins from wheat flour.

Background Cereal‐associated allergy is particularly considered a serious problem, because cereals are essential in our daily diet. Wheat proteins are classified into albumins, globulins and prolamins (insoluble gliadins and glutenins).

Reversible changes of the wheat γ46 gliadin conformation submitted to high pressures and temperatures

The structure of the wheat gamma 46 gliadin was investigated, in aqueous solutions, under high pressure or temperature by the use of ultraviolet and fluorescence spectroscopic techniques. We found that high pressure (above 400 MPa) induces a change in the protein conformation that results in a decrease of the polarity of the environment of aromatic amino acids. This new conformation was able to bind the hydrophobic probe, 8-anilino-1-naphtalene-sulfonic acid (ANS), indicating an increase in the gliadin surface hydrophobicity. Thermodynamic parameters of this conformational change were measured and infrared spectroscopy studies were used to probe the potential secondary structure modifications. The high stability of gamma 46 gliadin could be related to its elastic character, as the observed changes were always found to be reversible.

Conformation of wheat gluten proteins : comparison between functional and solution states as determined by infrared spectroscopy

The conformation of wheat gluten proteins in their functional hydrated solid state (doughy state) has been studied for the first time using attenuated total reflection infrared spectroscopy. The amide I band of functional gluten proteins reveals that, in addition to β‐turns and α‐helices, these proteins contain a significant amount of intra‐ and intermolecular extended β‐sheet structures. It appears that the solubilization of gluten proteins results in a major decrease of the amount of β‐sheet structures accompanied by an increase of the content of the β‐turn and α‐helical conformations. In addition, the α‐helices appears to be more distorded in solution than in the functional state. Furthermore, spectra of ω‐ and γ‐gliadins, which are two types of prolamins of differing amino acid sequence and conformation, confirm the results obtained on the functional protein system. These results suggest that viscoelastic gluten proteins may interact through aligned β‐sheets corresponding to their repetitive domains.

Biochemical basis of flour properties in bread wheats. II. Changes in polymeric protein formation and dough/gluten properties associated with the loss of low Mr or high Mr glutenin subunits

Abstract Polymeric protein plays a critical role in governing the functional properties of wheat flour. Wheat genetic lines lacking high M r and, similarly, low M r glutenin subunits from one, two or all three Glu-1 or Glu-3 loci, respectively, were thus used to investigate the effects of these polypeptides on glutenin polymer formation and dough/gluten properties. Polymer formation (quantity, size distribution) was studied by size-exclusion high-performance liquid chromatography (SE-HPLC) using extractable, unextractable and total protein from flour, as well as by diagonal electrophoresis using total protein extracts. The loss of Glu-1 or Glu-3 subunits had significant effects on the quantity of total, extractable and unextractable polymeric protein and on the dough and gluten properties of these lines. Dough and gluten properties were significantly correlated with the proportions of both total and unextractable polymers (a measure of the relative molecular size distribution of polymeric protein), although more strongly with the proportions of unextractable polymers in the case of Glu-1 null lines. The proportion of total polymeric protein decreased more markedly when all the Glu-3 subunits were deleted than when all the Glu-1 subunits were absent, which was in accordance with the relative quantities of these two types of the subunits in the grains. In contrast, loss of all the Glu-1 subunits, on an equal weight basis, reduced the amounts of the larger polymers to a much greater extent than the loss of all the Glu-3 subunits, reflecting more than the molecular size differences in these subunits. SE-HPLC and diagonal electrophoresis of total protein extracts from the triple Glu-1 and Glu-3 null lines also revealed that Glu-1 or Glu-3 subunits form large polymers on their own. When both high and low M r glutenin subunits were present together, however, the amount of large polymer was much greater than the sum of the amounts when only one group was present, suggesting a positive interaction between these two groups of subunits with respect to polymer formation.

Interfacial and emulsifying properties of lipopeptides from Bacillus subtilis

Abstract The fundamental surface-active properties at the oil/water interface and emulsifying properties of surfactin, iturin A and fengycin, lipopeptides from Bacillus subtilis, were investigated. All lipopeptides reduce rapidly the dynamic interfacial tension. Among lipopeptide families, surfactin is the most effective in terms of fundamental dynamic and equilibrium interfacial properties. Lipopeptides present intermediate properties in comparison with sodium dodecyl sulfate and β-lactoglobulin concerning the stabilizing effect towards creaming-flocculation and the resistance to coalescence. Among lipopeptides, iturin A seems to show the best resistance to creaming-flocculation whereas fengycin exhibits the highest resistance to coalescence properties.