The final established physicochemical properties of steamed bread made from frozen dough: Study of the combined effects of gluten polymerization,water content and starch crystallinity on bread firmness

The gluten polymerization behavior, water content, starch crystallinity and firmness of Chinese steamed bread made from frozen dough were investigated and their correlations were also established in this study. The decreased degree of gluten polymerization in steamed bread was observed by the enhanced SDS-extractable proteins (SDSEPs) upon frozen storage. Less incorporation of glutenin in the glutenin–gliadin crosslinking of steamed bread mainly contributed to the decreased degree of gluten polymerization. The decreased moisture of steamed bread had a significant negative correlation with the sublimated water in frozen dough (r = −0.8850, P < 0.01). Frozen storage also induced an increase in starch crystallinity and bread firmness. A multiple linear regression model with SDS-extractable proteins, water content and melting enthalpy of starch crystals of steamed bread accounted for 86% of the variance in the natural logarithm of firmness and further revealed that starch crystallinity mainly contributed to bread firmness.     

The effect of gluten on the retrogradation of wheat starch

The retrogradation of amylopectin in a wheat starch and a wheat starch/gluten (10:1) blend prepared by extrusion and containing 34% water (wet weight basis) was studied using X-ray diffraction, differential scanning calorimetry and NMR relaxometry during storage at constant water content and temperature (25 °C). For both samples, amylopectin ‘fully’ retrograded after 2–3 days storage, i.e. the different parameters monitored with time to follow the retrogradation had reached their maximum value, and crystallised predominantly into the A polymorph. Under the experimental conditions used, there was no evidence of any significant effects of the presence of gluten on the kinetics, extent or polymorphism of amylopectin retrogradation.     

Linear viscoelasticity of gluten: Decoupling of relaxation mechanisms

The influence of water content on the relaxation dynamics of mesoporous gluten networks has been explored in a wide range of temperatures. The systems were investigated in the linear viscoelastic region by means of stress relaxation, creep and numerical analysis of data. Time-temperature superposition principle and sticky reptation dynamics have been used to provide molecular interpretation of gluten relaxation. Overall, hydration influences relaxation behaviour of the system, which can be linked to changes in the secondary structure of gluten proteins with increase in water content. Relaxation spectra calculated with Tikhonov regularization revealed the remarkable influence of water on the long times relaxation processes of the material. Creep measurements and extraction of dynamic data with direct conversion of creep data via Laplace transform augmented the experimental timeframe of observations to low frequencies unattainable by standard frequency sweeps. The predominance of loss modulus at long times is attributed to migration of water within the nanopores of the structure. Samples also exhibit self-similar relaxation a characteristic of systems existing at a critical state. Two relaxation mechanisms can be distinguished: one arising from viscoelastic relaxation of protein chains and an additional stemming from poroelastic relaxation owing to migration of water in the system.     

Effects of composition on dough development and air entrainment in doughs made from gluten-starch blends

Gluten and starch are the two main ingredients of a wheat flour dough and it is expected that the extent of air occlusion into the dough would be affected by differences in their relative ratios. The objectives of this paper were to investigate the hydration and development of gluten and how these key events in dough mixing affected air occlusion in gluten-starch doughs. For gluten-starch doughs of the same gluten content, decreasing the water absorption shortened development time and decreased dough density. For formulations of the same water absorption, decreasing the gluten content prolonged the time to development and increased dough density, reflecting less net air entrainment into the dough. The ratios of gluten, starch and water strongly influenced the development of the dough into a good gas-holding material, with the extent of gas entrainment during mixing being evident in measurements of both dough consistency and dough development time.     

Comparison of structural features of reconstituted doughs affected by starches from different cereals and other botanical sources

Starch, as the main component of flour products, determines the physicochemical properties of dough. This work investigated the relationship of the physical properties of seven types of starches from various cereals with the structural features of reconstituted dough. Results of mixing and tensile properties analysis and scanning electron microscopy displayed that rice reconstituted flour exhibited maximum water absorption; pea reconstituted flour had higher dough stability; sweet potato dough had higher tensile resistance; highland barley dough had the greatest extensibility. Moisture distribution analysis revealed that various model dough showed remarkably different water distribution, which was distributed at T₂₁ (0.07–0.11 ms), T₂₂ (0.8–2.66 ms) and T₂₃ (10.0–20.82 ms). Correlation analysis indicated that large starch granules associated with good dough stability; amylose content of starch positively affected tensile resistance of dough; crystallinity of starch showed negative effects on water absorption; starch with higher crystallinity associated with greater dough stability.     

Migration of gluten under shear flow as a novel mechanism for separating wheat flour into gluten and starch

This paper describes a novel principle for the separation of wheat flour into starch and gluten in a concentrated medium. The process is based on the use of simple shear flow in a cone-and-cone device. The separation takes place in two steps. Initially, local segregation of gluten and starch phases occurs, leading to formation of macroscopically visible gluten patches distributed throughout the dough. This local segregation can be understood by considering the dough as a visco-elastic matrix containing an inert filler (starch). Further shearing leads to aggregation of those patches and migration (large-scale separation) towards the apex of the cone. As a result, the wheat dough is separated into a protein-poor fraction, containing less than 4% protein, and a protein-rich fraction containing almost 50% protein on a dry weight basis. However, under the process conditions used, upon a very long shearing, a redistribution of the aggregated gluten structures in the starch phase was observed, demonstrating a processing limit for the separation performance. Compared to traditional processing, the separation process presented shows opportunities for producing high quality gluten accompanied with significant water savings. Considering the fact that simple shear flow in steady rate is less harmful to gluten quality, such a separation process could benefit gluten quality.     

Deamidation of gluten proteins and peptides decreases the antibody affinity in gluten analysis assays

Wheat gluten is a widely used ingredient in the food industry due to its unique properties and relatively low price. Modification of wheat gluten makes it a versatile ingredient and, thus, increases its applicability in foods. Therefore, gluten proteins can be found in unexpected sources, and this makes the gluten-free diet challenging to follow. Deamidation is one way to modify protein structure. It increases solubility and surface activity of gluten improving its functionality, but consequently, also influencing the accuracy of quantification by immunoassays. In this study, the effect of deamidation on the antibody recognition with gluten analysis methods based on monoclonal R5, omega-gliadin or G12 antibodies was studied. Random deamidation decreased the intensities to 13–54% of the intensity obtained for the intact peptides. Deamidation representing the transglutaminase deamidation decreased the intensities to 4–8%. Deamidation of gluten proteins abolished the recognition by omega-gliadin and G12 antibodies and decreased the recognition of R5 by 600 times when analyzed by the sandwich method and 125 times by the competitive method. In conclusion, with all of the investigated gluten-specific antibodies, deamidation decreased the affinity of antibodies to gluten peptides and proteins, which needs to be considered when assays and regulations are developed for gluten-free products.     

Effect of hydrostatic pressure and temperature on the chemical and functional properties of wheat gluten III. Studies on gluten films

Numerous gluten preparations were produced by the variation of pressure and temperature. Optimal conditions for the production of gluten films on a laboratory-scale were by suspending of gluten (1 g) in a mixture of ethanol (3 mL), glycerol (0.5 g) and conc. formic acid (10 mL), casting and drying at 40 °C. Small-scale laboratory methods for the production of gluten films by casting and moulding were developed. Film strips obtained were examined by micro-extension tests, which resulted in curves similar to extensigrams for dough and gluten and allowed the determination of the resistance to extension, extensibility and elasticity. The results demonstrated that pressure treatment of gluten in combination with variable cultivars, temperature, process parameters and additives, allow the production of films with a wide range of rheological properties – from soft and smooth to strong and hard rubber like. Finally, it was demonstrated that the addition of fibres to gluten enhanced the stability of films. Thus, high pressure treatment allows a selective modification of gluten as raw material for film production. In comparison with conventional plastic films, gluten films have considerable advantages, because they can be produced from renewable plants and they are readily biodegradable.     

FT-Raman and FT-IR studies of the gluten structure as a result of model dough supplementation with chosen oil pomaces

The pomaces obtained after cold pressing oil production from oil seeds can be regarded as a source of many valuable nutrients such as unsaturated fatty acids, dietary fibre and antioxidants. The aim of the research was to determine the effect of five oil pomaces from black seed, hemp, pumpkin, milk thistle and primrose on the structure of gluten proteins. The model dough was supplemented with 3%, 6%, and 9% of the pomaces. Structural changes in gluten proteins were studied using Fourier transform Raman spectroscopy (FT-Raman) and Fourier transform infrared spectroscopy (FT-IR). Additionally, chemical composition of the pomaces was determined. Changes observed in the gluten structure resulting from the model dough supplementation with oil pomaces allow the pomace to be divided into two groups depending on the type and amount of fatty acids present in the pomaces. If the pomace contains a low number of fatty acids (black seed and pumpkin), pseudo-β-sheets are formed from β-turns and antiparallel-β-sheets in the gluten network. If the pomace contains a high number of fatty acids, non-aggregated β-structures are observed. Although the pomaces contain considerable amount of dietary fibre and polyphenols, comparison of the observed structural changes in gluten network with pomaces’ chemical composition indicates that the changes are connected with presence of fatty acids.     

Using the Gluten Peak Tester as a tool to measure physical properties of gluten

The functional properties of wheat are largely dictated by composition and interactions of the gluten proteins. All flours contain gliadin and glutenin, but produce baked products of varying quality, which provides evidence that gluten proteins from different wheats possess different properties. A common method to study differences in gluten properties, which is utilized in this study, is fractionation/reconstitution experiments to understand how various gliadin to glutenin ratios and how fractions from different wheat sources affect gluten aggregation properties. Gliadin and glutenin from a vital wheat gluten were fractionated with 70% ethanol and reconstituted at various gliadin to glutenin ratios. Gliadin and glutenin from a Canadian eastern soft, eastern hard and western hard wheat (14% moisture) were fractionated and substituted between flours at the native gliadin to glutenin ratio. Gluten combinations were evaluated with a Gluten Peak Tester at constant temperature and mixing. Varying gliadin to glutenin ratio showed that 50:50 is optimal for fast gluten aggregation while amount of glutenin dictates strength. Substitution experiments showed that replacing good quality gluten fractions with those from a lower quality wheat decreases gluten quality, and vice versa. Data also showed that cultivar specific differences in gliadin and glutenin are more important in dictating gluten strength (torque), while gliadin to glutenin ratio dictates aggregation time (PMT) independent of the source of fractions. The study demonstrated the ability of the improved method to evaluate gluten aggregation by controlling for all variables except the one being tested. The data also revealed information about gluten aggregation properties never before seen.     

A phenomenological analysis of wheat gluten viscoelastic response in retardation and in dynamic experiments over a large time scale

Dynamic measurements and retardation tests (creep and creep recovery) were combined systematically to characterise the different aspects of gluten rheology. Gluten flow behaviour exhibits extreme shear thinning and time-dependent viscosity. The viscoelastic contribution to the total strain behaves linearly over large strain and stress ranges; however, the material shows physical ageing and does not exhibit time translational invariance. In spite of these difficulties, it was possible, in the case of fresh gluten samples or after the material has been submitted to mechanical loading for a period long enough, to obtain the linear viscoelastic response over seven logarithmic decades of time or frequency by combining the data from dynamic measurements and from retardation tests. The method of Kaschta was used to calculate the discrete retardation spectrum from creep recovery data; the spectrum was then used to convert recovery data into storage and loss compliance and modulus. Converted recovery data match dynamic data satisfactorily in the case of fresh gluten. Some discrepancy was observed in the case of gluten submitted to previous mechanical history; it has been attributed to the effect of physical ageing. The storage and nonviscous loss compliance functions show that the extension of the viscoelastic plateau of gluten is very large. Their shape suggests a bimodal spectrum; however, this point would need further confirmation.     

Effects of ultrasound-assisted freezing on the water migration of dough and the structural characteristics of gluten components

The effects of ultrasound-assisted freezing on the freezing time and water migration of dough, and the structural characteristics of gluten components were investigated. The effects of ultrasound-assisted freezing in the whole immersion freezing process (UWF) on the freezing time were better than those of ultrasound-assisted freezing in the maximum ice crystal generation zone. The shortest freezing time was obtained at 80 W/L, and was 577 s shorter than that with traditional immersion freezing. The UWF treatment at 80 W/L significantly (p < 0.05) affected the absorption enthalpy, freezable water content and water migration of frozen dough. In UWF compared with traditional immersion freezing, the SH content of gluten, glutenin and gliadin was significantly (p < 0.05) higher, by 12.06%, 27.55% and 21.65%, respectively. The surface hydrophobicity of gluten, glutenin and gliadin in UWF treated samples significantly (p < 0.05) decreased, by 19.67%, 13.21% and 9.17%, respectively. The secondary structure of gluten components was also significantly changed by UWF. The network of gluten, the chain structure of glutenin and the gliadin particles were all changed by UWF treatment. These findings indicated that UWF is an effective method to improve the moisture distribution in dough and reduce the damage to protein molecular structure caused by freezing.     

Effects of transglutaminase on the rheological and noodle-making characteristics of oat dough containing vital wheat gluten or egg albumin

Incorporating exogenous proteins into food production is a common practice for improving processing characteristics. In the present study, oat dough containing 15% (w/w, blends of protein-oat flour basis [POB]) vital wheat gluten (VWG) or 15% (w/w, POB) egg albumin (EA) was used to produce noodles with or without gluten (i.e., gluten-free). The rheological and noodle-making characteristics of oat dough containing exogenous proteins and the effects of added transglutaminase (TGase) were examined. The results indicate that the extent of TGase’s modification of the thermomechanical and dynamic rheological characteristics (G′ and G″) is dependent on the source of exogenous proteins in the oat dough. By adding 1.0% (w/w, POB) TGase, the cooking qualities of the resulting noodles (i.e., those containing VWG and EA) were significantly elevated with lower cooking loss; the elasticity of both types of noodles increased. The effects of TGase in different dough systems were analyzed by SDS-PAGE. In oat dough prepared with VWG, TGase was shown to catalyse the cross-linking of both oat protein and gluten protein; however, oat protein acted as the only substrate of TGase in the noodles that had been prepared with EA.     

Prediction of CIELab data and wash fastness of nylon 6,6 using artificial neural network and linear regression model

We tried to predict the CIELab data and wash fastness values of scoured nylon 6.6 knitted fabric dyed with 1:2 metal-complex acid dyes and aftertreated using three different methods named as syntan, syntan/cation and full backtan by artificial neural network (ANN) with Levenberg-Marquardt algorithm and regression models. Afterward, the predicting performance of these models was tested and compared with each other using unseen data sets. We were able to achieve to predict the all colorimetric data satisfactorily such as L*, a*, b*, C, h ^o and wash fastness performance using both models. The statistical findings indicated that the regression models provide more accurate prediction for all colour data with an average error of 1% contrast to previous study. In terms of prediction of fastness, artificial neural network is a bit more useful than regression models for prediction of staining value on the nylon part of adjacent multifiber.     

Impact of late-season N fertilisation strategies on the gluten content and composition of high protein wheat grown under humid Mediterranean conditions

The rise in high protein common wheat in humid Mediterranean areas has determined a need to compare specific and effective nitrogen (N) fertilisation protocols in order to increase their end-use value. The aim of the work was to assess the impact of late-season N fertilisation strategies on grain yield and protein content (GPC), gluten fraction composition, and rheological traits. Different applications and types of fertiliser (soil applied ammonium nitrate, soil applied urea, foliar applied urea and a foliar applied commercial fertiliser) were distributed at the same rate (30 kg N ha⁻¹) in a field experiment in NW Italy, during three growing seasons. A control without any late-season N fertilisation was also considered. All the treatments received 130 kg N ha⁻¹ as ammonium nitrate (AN), which was split between tillering and the beginning of the stem elongation growth stages.None of the compared late-season N fertilisations significantly affected canopy greenness and stay green duration during the grain filling period, or the grain yield, test weight, and thousand kernel weight, although the foliar application significantly increased foliage burning (+9.8%). The late application of N consistently increased GPC (+1.1%) and dough strength (W, +21%) in the different growing seasons. The type of fertilisation strategies clearly affected the gluten content and rheological parameters: AN was more effective than urea as a soil top-dressed applied fertiliser in increasing W (+10%), as a result of a higher rise in the GPC content (+0.5%) and extensibility (L, +11%). The foliar application at anthesis, at the same N rate, led to a comparable GPC and W with those of the soil top-dressed granular fertiliser. Only a weak effect of granular urea on y/x type HMW was observed for the gluten composition. Conversely, a notable influence of year was observed (i.e. GS/Glia and y/x type HMW), which in turn resulted in a significant impact on W and P and on the aggregation time and aggregation energy.This study offers a further contribution to the improvement of specific N fertilisation strategies in order to enhance the wheat quality according to its end-use value.     

Foaming properties of gluten and acetylated gluten: Studies of the mathematical models to describe liquid drainage

The foaming properties of gluten and acetylated gluten were studied at various concentration values (1%, 5%, 10% and 20%). Acetylated gluten was prepared by acetylation of gluten with acetic anhydride in presence of sodium hydroxide as catalyst. The foaming properties were characterised by measuring foam stability and drainage. It was found that foam made from acetylated gluten is more abundant and stable than the foam made from gluten studied in the whole range of concentration, i.e. 1–20%.     

A modeling approach in the interpretation of starch pasting properties

In this work, starch pasting curves were reinterpreted with suitable models to show deficiency of widely used starch pasting parameters in the literature. The aim was to attract scientific attentions to the behavior and dynamics of the curve with respect to process parameters instead of values on the curve. Mainly, pasting curve was separated into four parts combining sigmoidal gelatinization model, exponential thinning model and Arrhenius temperature model. For the gelatinization part, starch swelling rate, water binding capacity and starch resistivities to heat and shear might be compared by the proposed model parameters. Amylose and damaged starch contents of starches had a good relation with Arrhenius and exponential model parameters. Activation energy values gave clues about retrogradation rate of starches and changed between 7142 and 17,327 kJ/mol.     

Low temperature suspension polymerization of methyl methacrylate for the preparation of high molecular weight poly(methyl methacrylate)/silver nanocomposite microspheres

In order to prepare high molecular weight poly(methyl methacrylate) (PMMA)/silver nanocomposite microspheres, methyl methacrylate was suspension-polymerized in the presence of silver nanoparticles at low temperature with 2,2′-azobis(2,4-dimethylvaleronitrile) as an initiator. The rate of conversion was increased by increasing the initiator concentration. When silver nanoparticles were added, the rate of polymerization decreased slightly. High monomer conversion (about 85 %) was obtained in spite of low polymerization temperature of 30°C. Under controlled conditions, PMMA/silver microspheres with various number-average degrees of polymerization (6,000–37,000) were prepared. Morphology studies revealed that except for normal suspension microspheres with a smooth surface, a golf ball-like appearance of the microspheres was observed, due to the migration and aggregation of the hydrophilic silver nanoparticles at the sublayer beneath the microsphere’s surface.     

Study of the impact of wheat flour type,flour particle size and protein content in a cake-like dough: Proton mobility and rheological properties assessment

The study of food products is always a challenge due to the number of components involved and the interactions that may occur between them. Water is a particular ingredient which interacts with all hydrophilic compounds, although affinities may differ for limiting water amount. During this study, results obtained using ¹H NMR on cake dough were compared in terms of the effects of flour type (soft or medium hard), the addition of gluten (5%–20%) and the use of soft flour fractions (flour particle fractions smaller or larger than 50 μm). T₂ values and the signal intensities of different proton populations were studied as a function of the wheat protein contents of dough samples. Physicochemical characterization methods were used to better understand how the origin and particle size of flour might impact the hydration properties and mobility of a model system. Increasing the protein content in dough samples was related to an increase of the mobility of fat protons and of the least mobile proton population (relaxation times ranging from 175 to 180 ms and from 5 to 7 ms, respectively).