Influence of sodium chloride on shear flow induced starch–gluten separation from Soissons wheat dough

Wheat dough can be separated into a starch-rich and a gluten-rich fraction by subjecting the dough to curvilinear shear flow. This paper presents the effect of salt (NaCl) addition on the shear-induced separation process. The separation (defined as the changes in protein concentration in the various layers, compared to the starting material) was promoted by NaCl addition up to a concentration of 4 w%. Dough without NaCl showed limited separation, but this effect could be partly compensated by a decreased processing time. Rheology measurements did not show clear differences in G′ and tan δ value, for dough with different NaCl concentration. But, shear stress and normal force did vary for various NaCl concentrations when applying a constant shear rate.     

Evaluation of Lepidium sativum seed and guar gum to improve dough rheology and quality parameters in composite rice–wheat bread

The effects of hydrocolloids in rice–wheat flour were studied. Hydrocolloids at 0%, 0.3%, 0.6% and 1% w/w (flour basis) and guar (G), Lepidium sativum seed (L) and guar-L. sativum seed (GL) gum were tested as additives to the rice/flour in various combinations. The quality parameters for the experiment were assessed with farinography, extensography, amylography and texture profile analysis. The evaluation of dough rheology showed that water absorption, dough development time, dough stability and viscosity all increased with the addition of hydrocolloids alone or in a combination. It was demonstrated that G₁L₁ promoted the highest effect. The mixing tolerance index and gelatinization temperature decreased with an increased hydrocolloid concentration. Extensibility value for the dough that incorporated guar and L. sativum seed gum increased with increasing hydrocolloid concentration from 0.3% to 0.6% and then decreased at 1%. The water activity of all bread didn't have significant differences with increasing hydrocolloids concentration but this parameter 24 decreased during storage. Firmness decreased with increasing hydrocolloid concentration and increased with increasing storage time. The sensory evaluation by a consumer panel gave the higher score for overall acceptability to G_0.3L_0.3 and G_0.3L_0.6 samples. The results also showed that G₁L₁, G₁L_0.6 and G_0.6L₁ samples had high specific volume and porosity.     

Steady and dynamic shear rheology of sweet potato starch–xanthan gum mixtures

The effect of xanthan gum at different concentrations (0.2–0.6% w/w) on the rheological properties of sweet potato starch (SPS) pastes was evaluated under steady and dynamic shear conditions. The presence of xanthan resulted in an increase in the consistency index and vane yield stress of SPS. The effect of temperature on the apparent viscosity of SPS–xanthan mixtures is well described by the Arrhenius equation. Dynamic moduli (G′, G″, and η^*) values of the mixtures increased with an increase in xanthan concentration while the tan δ values decreased. The addition of xanthan appeared to contribute to the elastic properties of the weak network of the SPS pastes. The structure development rate constant (k) of gelation during ageing was strongly influenced by the presence of xanthan. This suggests that the phase separation process caused by the incompatibility phenomena between the amylose component in starch and xanthan can increase the elastic characteristics of the SPS–xanthan mixtures.     

Changes in structure and aroma release from starch–aroma systems upon α-amylase addition

The influence of starch hydrolysis by α-amylase addition on structural properties and aroma release from starch–aroma systems was studied. A food model system composed of aqueous tapioca starch dispersion (4 g dry starch/100 g dispersion) and one aroma compound (menthone) was investigated. Structure breakdown and related changes in starch fraction (amylose) were measured by rheology and iodine-binding. Menthone release from the aroma-starch system in the headspace was followed by proton transfer reaction-mass spectrometry (PTR-MS) upon starch hydrolysis. A slightly higher viscosity was found for the starch–menthone system compared to the starch system without menthone upon α-amylase addition. One could hypothesise that menthone acts as a kind of nucleation agent for inducing structure build-up of starch segments, hindering starch degradation. An extensive aroma release from aroma–starch systems upon α-amylase addition was expected, but, instead, just a slight volatile increase was found after a starch hydrolysis time of 60 min. It is suggested that aroma release is the result of several superimposed effects ranging from viscosity effects to interactions between aroma compounds and starch degradation products.     

Dough rheology and baking performance of wheat flour–lupin protein isolate blends

The impact of addition of two lupin protein isolates (LPI), enriched either in proteins belonging to globulin (LPI G) or to albumin (LPI A) fraction, on wheat flour dough and bread characteristics was investigated. LPI addition increased the dough development time and stability plus the resistance to deformation and the extensibility of the dough. The presence of LPI proteins in dough affected bread quality in terms of volume, internal structure and texture, while extra gluten addition to the blends to compensate for wheat gluten dilution, resulting from LPI addition, led to an improvement of bread quality characteristics. Generally, the incorporation of LP isolates to wheat flour delayed bread firming. The results obtained are discussed in terms of a possible action of LPI particles as a filler of the gluten network and partly in terms of possible interactions that take place between the gluten protein constituents and those of lupin.     

Combined effects of wheat gluten and carboxymethylcellulose on dough rheological behaviours and gluten network of potato–wheat flour-based bread

Incorporating high level of potato flour into wheat flour enhances nutritional values of bread but induces a series of problems that lead to the decline of the bread quality. To overcome the barrier, wheat gluten and carboxymethylcellulose (CMC) were added into potato–wheat composite flour to improve dough machinability and bread quality. The rheological properties, thermo-mechanical properties and microstructures of dough were investigated. The results showed that the interaction between gluten and CMC mitigated the discontinuity of gluten matrix and gluten protein aggregation caused by the addition of potato flour, which yielded a more branched and compact gluten network. The compact three-dimensional viscoelastic structure induced improvements of gas retention capacity and dough stability, making it mimic the machinability properties of wheat flour dough. Bread qualities were apparently improved with the combined use of 4% gluten and 6% CMC, of which specific volume increased by 42.86%, and simultaneously, hardness reduced by 75.93%.     

Understanding high pressure-induced changes in wheat flour–water suspensions using starch–gluten mixtures as model systems

The effect of high pressure (HP) on wheat flour–water suspensions was investigated. Suspensions were treated for 10 min at 200–600 MPa. HP-treatment significantly increased the consistency of the flour suspensions, as studied by frequency sweep tests. Temperature sweeps revealed that HP-induced starch gelatinisation, with a sigmoidal-shaped correlation between degree of gelatinisation and treatment pressure. Analysis of protein solubility in different buffers indicated the HP-induced formation of urea-insoluble complexes and/or disulphide bonds. Furthermore, the effects of HP on the isolated components wheat starch and gluten were studied, and starch–gluten mixtures were used as a model system for flour. A negative effect of gluten on the consistency increase of starch suspension was observed. Comparing the rheological parameters of HP-treated wheat flour suspensions to those of starch suspensions, confirmed the weakening effect of gluten. However, the presence of gluten in flour could not fully explain the differences between starch and flour suspension.     

Interfacial characteristics and microchannel emulsification of oleuropein-containing triglyceride oil–water systems

This study investigated the adsorption characteristics of olive leaf water extract and its major phenolic compound, oleuropein, at the triglyceride oil–water interface. We also investigated the preparation characteristics of food-grade triglyceride oil-in-water (O/W) emulsions stabilized by oleuropein using microchannel (MC) emulsification. Refined soybean oil, extra virgin olive oil, refined olive oil, and medium-chain triacylglyceride (MCT) oil were used as triglyceride oils. Both olive leaf extract (OLE) and highly purified oleuropein had a pronounced ability to decrease the interfacial tension at the refined soybean oil–water interface. The packing of oleuropein molecules at the triglyceride oil–water interface was estimated on the basis of their surface excess concentration and area occupied per molecule, determined from the Gibbs adsorption equation. MC emulsification was performed using a silicon grooved MC array plate (model CMS6-2). The continuous aqueous phase contained 0.6 wt.% of oleuropein. Monodisperse, oleuropein-stabilized O/W emulsions with an average droplet diameter of 25 μm and coefficient of variation (CV) of < 5% were produced in all systems, except the MCT oil-containing system, even in the absence of a cross-flowing continuous phase. This successful MC emulsification was observed without droplet coalescence for 15 h of continuous operation. Our findings demonstrate that the use of oleuropein, which has an interfacial activity, is capable of producing monodisperse O/W emulsions using MC emulsification and stabilizing the generated oil droplets when appropriate types of triglyceride oils are used.     

Effect of the incorporation of antioxidants on physicochemical and antioxidant properties of wheat starch–chitosan films

Blend edible films were prepared from wheat starch (WS) and chitosan (CH) with glycerol as plasticizer. Four active ingredients (antioxidants) were added, namely basil essential oil, thyme essential oil, citric acid and α-tocopherol. The starch:antioxidant mass ratio was 1:0.1. Prior to characterisation, the films were conditioned at 25 °C–53%RH as to their structural, mechanical, optical and barrier properties. The antioxidant capacity of the active ingredients was determined by means of a spectrophotometric method. The incorporation of antioxidants led to a heterogeneous film microstructure, mainly in those containing α-tocopherol, which affected the surface roughness. Yellowness was induced in films when α-tocopherol was added and no notable colour changes were observed in the other cases, although all the antioxidants increased the transparency of the films. Despite of the fact that the mechanical properties were barely affected by the incorporation of antioxidants, citric acid promoted an increase in the elastic modulus but a decrease in film stretchability. The water vapour barrier properties of the films were only slightly improved when citric acid and α-tocopherol were added, whereas the oxygen barrier properties were significantly improved in all cases. The greatest antioxidant capacity of the films was reported for films containing α-tocopherol, which exhibited the highest antioxidant power.     

Effect of processing history on the functional and structural characteristics of starch–fatty acid extrudates

Normal maize starch was extruded with and without the addition of fatty acid potassium salts in a twin screw cooker extruder equipped with a slit die rheometer, at 100, 120, 140 or 160 °C barrel temperatures and at screw speeds 20, 91, 161 or 227 rpm. The in line melt viscosity measurements showed that the flow behaviour of the starch system was influenced by the addition of either myristic or palmitic acids used. The examination of functional properties of the extrudates such as bulk density, water solubility index, expansion ratio, degree of gelatinization and water adsorptivity indicated that the addition of fatty acids affected the functionality of starch systems. That is, the extrudate texture became more cohesive and compact whereas the water solubility exhibited by the system was decreased. Structural studies indicated that the crystallinity of starch–fatty acid extrudates was higher than that of the starch systems without fatty acid whereas all extrudates exhibited high glass transition temperatures and their structure was very rigid and brittle.     

Effect of organic calcium salts–inulin systems on hydration and thermal properties of wheat flour

The aim of this work was to study the effect of calcium acid salts–inulin systems on hydration and thermal properties of wheat flour dough. Wheat flour was enriched with calcium lactate (CaLa₂) or calcium citrate (Ca₃Ci₂) (1080–2520 ppm Ca) and inulin (In) (1%–13%, w/w flour basis). Water absorption (W_abs), moisture content (M_cont), water activity (a_w) and relaxation time (λ) of dough were analyzed. Pasting properties during heating–cooling process were studied: peak viscosity (PV), breakdown (BD), final viscosity (FV) and setback 1(SB1) were determined. Temperatures (T_pI, T_pII) and enthalpy (?H_gel) of gelatinization of dough were analyzed by DSC. Samples with Ca and In presented lower W_abs than control sample with an In² dependence, with slight difference between both surface responses. More time for dough development (t_d) was necessary with Ca₃Ci₂ than with CaLa₂, being t_d independent of calcium content at In level (≥ 6.5%). Dough with Ca₃Ci₂ was more stable with less degree of softening than CaLa₂-dough, due to the protein stabilizing effect of citrate ion (Hofmeister series) with a maximum at 6.5% In. M_cont and λ decreased with the increase of In, independently of calcium. Hydration properties directly influenced pasting parameters. The increase in In content decreased viscosity (PV, FV) without affecting BD. SB1 behavior suggests the formation of pastes with low and high stability with CaLa₂ and Ca₃Ci₂, respectively. Gelatinization degree decreased (40%) and retarded (?T = 10 °C) at high levels of both ingredients. CaLa₂ had more influence in hydration and thermal properties of wheat flour–inulin blends, enhancing a high degree of inhibition of gelatinization and leading to pastes with low viscosity after cooling. This behavior was influenced by the presence of inulin.     

Physicochemical characteristics and in vitro bile acid binding and starch digestion of β-glucans extracted from different varieties of Jeju barley

Physicochemical properties of six different varieties of barley and their β-glucans were evaluated along with in vitro bile acid binding and starch digestibility for health beneficial effects. β-Glucan concentrations in less-hulled, beer, black, waxy-naked, naked, and blue barley were 3.44, 3.46, 6.08, 6.75, 6.45, and 5.91%, respectively. Viscosity of waxy-naked barley flour was the highest. While the yield of β-glucan from waxy-naked barley after extraction was 95.49%, less-hulled barley was 70.09%. As the increase of β-glucan purification, in vitro bile acid binding was increased when compared with cholestyramine and cellulose. In vitro starch digestibility of barley flour and the mixture of potato starch with β-glucan were increased by heat and β-glucan concentration. Estimated glycemic index (GI) calculated based on in vitro starch digestibility was decreased by increasing β-glucan. These results suggest that the physicochemical properties of barley were dependent on the variety of barley and especially β-glucan was involved.     

Correlation of rainfall and levels of deoxynivalenol in wheat from Uruguay, 1997–2003

A total of 286 wheat samples for human consumption collected during 1997–2003 from four wheat-producing localities of south-western Uruguay were screened for deoxynivalenol (DON). Quantification was carried on by an immunochemical method using immunoaffinity columns and fluorimetric detection. The incidence of DON was high during the whole survey (58.5–100%), except in 1998 and 1999 in which no contamination occurred. During 2001 and 2002, 100% of samples contained detectable levels of DON, being the mean DON contents 6593 and 5880 µg kg^?1, respectively. The annual maximum levels ranged from 8800 to 11,400 µg kg^?1. A positive correlation between DON levels and precipitation was seen. The 70% of wheat samples destined for human consumption were contaminated with DON. To avoid the introduction of contaminated materials into the food chain process, the adoption of regular screening of the DON level in wheat is recommended, particularly in years with heavy rainfall during the flowering-to-early stages of grain maturity months.     

The physicochemical characteristics and hydrophobicity of high amylose starch–glycerol films in the presence of three natural waxes

The film forming behaviour and hydrophobicity of high amylose (HA) starch in the presence of three different natural waxes (beeswax, candelilla wax and carnauba wax) were studied in the presence and absence of Tween-80. The HA starch:glycerol (G) ratio was maintained at 80:20 (on dry solid basis) and the concentration of wax was varied from 5% and 10% (w/w). The melted wax samples were homogenized with HAG dispersion with or without Tween-80 and the films were prepared by solution casting. The hydrophobicity and water-barrier properties in these films were determined by using contact angle (CA), water vapour permeability (K_w) tests, and water sorption isotherm at 0.529 RH and 20 °C. The K_w values of the HAG films decreased significantly (p < 0.05) with the addition of 5% concentration of these waxes. Then the addition of Tween-80 to the HAG + wax films increased the K_w values significantly (p < 0.05). The presence of these waxes in the presence and absence of Tween-80 resulted into different sorption isotherms and the water adsorptivity and moisture diffusion coefficient values were also affected. The presence of Tween-80 increased the CA in HAG + carnauba wax films while the CA was found to decrease in the case of other two waxes. The highest hydrophobicity was observed in HAG + carnauba wax + Tween-80 films in which the CA was >80.0° both at 5% and 10% (w/w) wax concentration. These higher CA values in HAG + carnauba wax + Tween-80 films were found to be related to the higher surface roughness in these films.     

Relevance of the air–water interfacial and foaming properties of (modified) wheat proteins for food systems

A shift from animal protein- to plant protein-based foods is crucial in transitioning toward a more sustainable global food system. Among food products typically stabilized by animal proteins, food foams represent a major category. Wheat proteins are ubiquitous and structurally diverse, which offers opportunities for exploiting them for food foam and air–water interface stabilization. Notably, they are often classified into those that are soluble in aqueous systems (albumins and globulins) and those that are not (gliadins and glutenins). However, gliadins are at least to an extent water extractable and thus surface active. We here provide a comprehensive overview of studies investigating the air–water interfacial and foaming properties of the different wheat protein fractions. Characteristics in model systems are related to the functional role that wheat proteins play in gas cell stabilization in existing wheat-based foods (bread dough, cake batter, and beer foam). Still, to further extend the applicability of wheat proteins, and particularly the poorly soluble glutenins, to other food foams, their modification is required. Different physical, (bio)chemical, and other modification strategies that have been utilized to alter the solubility and therefore the air–water interfacial and foaming properties of the gluten protein fraction are critically reviewed. Such approaches may open up new opportunities for the application of (modified) gluten proteins in other food products, such as plant-based meringues, whippable drinks, or ice cream. In each section, important knowledge gaps are highlighted and perspectives for research efforts that could lead to the rational design of wheat protein systems with enhanced functionality and overall an increased applicability in food industry are proposed.     

Structure–mechanism relationship of antioxidant and ACE I inhibitory peptides from wheat gluten hydrolysate fractionated by pH

The aims of this study were to assess bioactive properties (ACE inhibition and antioxidant capacity) from wheat gluten hydrolysate peptides fractionated by pH (4.0, 6.0 and 9.0), to determine peptide action mechanism, and to relate it to the secondary structure and functional groups of peptides. Gluten hydrolysate extracts (GHE) were enriched in peptides with medium hydrophobicity and molecular weight (≈ 60% MH and 5.5 kDa, respectively). Gluten peptides inhibited ACE I by uncompetitive mechanism and a direct relationship between α-helix structure and IC50% value was obtained (r = 0.9127). TEAC and cooper chelating activity from GHE 6.5 were the highest and directly correlated with MH peptides. GHE 9.0 had high carotene bleaching inhibition (47.5 ± 0.3%) and reducing power activity (163.1 ± 2.9 mg S₂O₃^2 − equivalent g^− 1 protein), which were directly related to disulfide bonds content of peptides (r = 0.9982 and 0.9216, respectively). pH was a good alternative to select bioactive peptides from wheat gluten hydrolysate.