How manipulation of wheat bran by superfine-grinding affects a wide spectrum of dough rheological properties

The present study explored the effect of size reduction by superfine grinding on the performance and rheological properties of bran-enriched dough. Coarse (D₅₀ = 328.98 μm) and superfine-ground (D₅₀ = 50.76 and 28.37 μm) wheat brans were incorporated into the wheat dough to replace 10–30% of plain flour. Both fundamental and empirical tests were performed to assess the mixing properties, pasting properties, large deformation rheology, small deformation rheology, and stickiness of the dough. With the increasing amount of bran added, dough water absorption capacity increased, while the dough became less sticky and more rigid. Superfine grinding reduced the water retention capacity of the bran by 17–20%. Dough fortified with the finest bran (D₅₀ = 28.37 μm) showed an overall better stability and uniaxial extensibility. However, the results suggested that superfine grinding not necessarily improve every aspect of dough performance, particularly the pasting properties. High peak and final viscosity were observed for dough fortified with superfine bran, indicating their end products, such as noodle, might exhibit high stickiness after cooking, and a high degree of starch retrogradation. Results of this study contributed to a better understanding of the modification effect of superfine grinding on dietary fibre.     

Potential use of exogenous lipases for DATEM replacement to modify the rheological and thermal properties of wheat flour dough

The effect of two lipases and DATEM at different concentrations on the rheological and thermal properties of white and whole wheat flour doughs was determined by farinograph, extensograph, texture analyzer and differential scanning calorimetry. Lipases provided similar or better results than that of DATEM on decreasing softening degree and stickiness, and increasing stability, maximum resistance to extension and hardness. Extensibility and energy did not change with lipases, but decreased with DATEM. Lipases and DATEM slightly modified the transition temperatures and enthalpies of ice-melting and starch gelatinization, but significantly increased the moisture and unfrozen water contents, and decreased the solid concentration in unfrozen water. The greatest effect of lipases was observed on decreasing the peak temperature and increasing the enthalpy of amylose–lipid complex dissociation. The changes in the rheological and thermal properties were almost independent of the concentration levels tested, and were mostly reduced when whole wheat flour was used. The improvement in the dough properties by lipases is possibly related to the in situ formation of surface active compounds from endogenous flour lipids. Presumably, these compounds are already located in the right positions in dough, where they might have higher interaction potentials than DATEM with the dough components.     

Feature of air classification product in wheat milling: Physicochemical,rheological properties of filter flour

Wheat filter flours are by-products obtained from air-classification of wheat flour. Physicochemical and rheological properties of wheat filter flours were investigated in the present study. Average values of crude protein, gluten, lipid and damaged starch content of filter flours were higher than those of standard flours for the same batch. The positive correlation of particles with size <20 μm and damaged starch was found. Moreover, the filter flours had higher water absorption, stability time except head milling filter flour samples. Short peak time and low peak viscosity were also observed. Different composition of wheat filter flours may be an important factor influencing its properties. This study is very useful for exploring the utilization of wheat filter flours in the food industry.     

Assessment of commercial milling potential of hard wheat by measurement of the rheological properties of whole grain

The single-kernel characterisation system (SKCS) 4100 instrument has previously been shown to provide in situ measurements of the rheological properties of the bran and endosperm layers of wheat, otherwise only possible following their isolation by dissection or machining. The current study has confirmed that endosperm maximum stress (endosperm strength (ES) as measured using the SKCS 4100 correlates highly (r=0.898$r=0.898$) with compressive strength (maximum stress, σ_max) measurements performed on specimens of endosperm tissues of known dimensions, isolated from different subsamples of the same bulk wheat samples. This provides a means of scaling the stress axis of the crush–response profile plots to the Instron scale (MPa) so that the SKCS endosperm stress/strain curves for hard wheat, soft wheat and durum can be compared with Instron results presented in the literature. In addition, a simple method for the measurement of ES and stiffness, using the SKCS 4100, has been developed. The method has been shown to rank wheat samples according to their performance when processed on a 650 kg/h pilot mill. The criterion against which the SKCS-derived rankings were compared was the Milling Quality Index, which uses both the percentage flour extraction and Branscan speck count measurements.     

Effects of endoxylanases,vital wheat gluten,and gum Arabic on the rheological properties,water mobility,and baking quality of whole-wheat saltine cracker dough

The aim of this study was to improve the baking quality of whole-wheat saltine cracker (WWSC) using endoxylanases, vital wheat gluten (VWG), and gum Arabic. SRC results showed both water-SRC and sucrose-SRC of soft white whole-wheat flour (SWWW) were significantly reduced by gum Arabic (r = 0.94, P < 0.05). Alveograph results indicated that the tenacity and extensibility of the whole-wheat dough (WWD) were increased by VWG. Rheometer G′ and G″ moduli increased with higher addition levels of endoxylanases, VWG, and gum Arabic. Low-field nuclear magnetic resonance (LF-NMR) detected three CPMG proton populations (T₂₁, T₂₂, and T₂₃) in WWD. T₂₁ peak area ratio (tightly bound water) reduced and T₂₂ peak area ratio (less tightly bound water) increased with the levels of each additive. LF-NMR results revealed increased water mobility from T₂₁ population to T₂₂ population with addition of these additives, which was beneficial for gluten to form a continuous network. Both stack height and specific volume of WWSC were improved by the use of endoxylanases, VWG, and gum Arabic, but the breaking strength varied. The results of Orthogonal experimental design showed that the most-improved quality WWSC could be produced by combining 0.035% endoxylanases, 1.5% VWG, and 1.5% gum Arabic into SWWW flour.     

Effect of hydrostatic pressure and temperature on the chemical and functional properties of wheat gluten: Studies on gluten, gliadin and glutenin

The effect of hydrostatic pressure (0.1–800 MPa) in combination with various temperatures (30–80 °C) on the chemical and physical properties of wheat gluten, gliadin and glutenin was studied. Chemical changes of proteins were determined by extraction, reversed-phase high-performance liquid chromatography (HPLC), sodium dodecylsulphate (SDS) polyacrylamide gel electrophoresis (PAGE), circular dichroism (CD) spectroscopy, thiol measurement and studies on disulphide bonds. Rheological changes were measured by extension tests and dynamic stress rheometry. Treatment of gluten with low pressure (200 MPa) and temperature (30 °C) increased the proportion of the ethanol-soluble fraction (ESF) and decreased gluten strength. The enhancement of both pressure and temperature provoked a strong reduction of the ESF and the thiol content of gluten. Within gliadin types, cysteine containing α- and γ-gliadins, but not cysteine-free ω-gliadins were sensitive to pressure and were transferred to the ethanol-insoluble fraction. Disulphide peptides isolated from treated gluten confirmed that cleavage and rearrangement of disulphide bonds were involved in pressure-induced reactions. Increased pressure and temperature induced a significant strengthening of gluten, and under extreme conditions (e.g. 800 MPa, 60 °C), gluten cohesivity was lost. Isolated gliadin and glutenin reacted differently: solubility, HPLC and SDS-PAGE patterns of gliadin having a very low thiol content were not influenced by pressure and heat treatment; only conformational changes were detected by CD spectroscopy. In contrast, the properties of isolated glutenin having a relatively high thiol content were strongly affected by high pressure and temperature, similar to the effects on total gluten.     

Investigation of the effect of conditioning on the fracture of hard and soft wheat grain by the single-kernel characterization system: A comparison with roller milling

A study has been carried out on selected hard and soft Australian wheats to determine the effect of conditioning on the crush-response profiles (CRPs) measured using the single-kernel characterization system (SKCS 4100). In addition, the fragmentation patterns that resulted from crushing in the SKCS have been compared with those that resulted from the first break stage of roller milling. It was found that the CRPs were changed significantly (P<0.05) as a result of conditioning. In particular, the rheological parameters shell stiffness and strength and endosperm strength all decreased following conditioning. The fragmentation patterns, assessed using low-resolution microscopy and particle size analysis, that resulted from the crushing of unconditioned wheat in the SKCS were the closest match with those that resulted from first break milling of conditioned wheat. These results show how the SKCS may be used to monitor the progress of wheat conditioning prior to milling. They also provide support for the use of SKCS measurements on unconditioned wheat for the prediction of milling performance.     

Biochemical markers: Efficient tools for the assessment of wheat grain tissue proportions in milling fractions

To produce safe and healthy whole wheat food products, various grain or bran dry fractionation processes have been developed recently. In order to control the quality of the products and to adapt these processes, it is important to be able to monitor the grain tissue proportions in the different milling fractions produced. Accordingly, a quantitative method based on biochemical markers has been developed for the assessment of grain tissue proportions in grain fractions. Grain tissues that were quantified were the outer pericarp, an intermediate layer (including the outer pericarp, the testa and the hyaline layer), the aleurone cell walls, the aleurone cell contents, the endosperm and the germ, for two grain cultivars (Tiger and Crousty). Grain tissues were dissected by hand and analysed. Biochemical markers chosen were ferulic acid trimer, alkylresorcinols, para-coumaric acid, phytic acid, starch and wheat germ agglutinin, for outer pericarp, intermediate layer, aleurone cell walls, aleurone cell contents, endosperm and germ respectively. The results of tissue quantification by hand dissection and by calculation were compared and the sensitivity of the method was regarded as good (mean relative errors of 4% and 8% for Crousty and Tiger outer layers respectively). The impact of the analytical variability (maximum 13% relative error on coarse bran) was also regarded as acceptable. Wheat germ agglutinin seems to be a promising marker of wheat germ: even if the quantification method was not able to quantify the germ proportions in milling fractions, it was able to classify these fractions according to their germ content. The efficiency of this method was tested, by assessing the grain tissue proportions of fractions exhibiting very different compositions such as flour, bran and aleurone-rich fractions obtained from three different grain or bran dry fractionation processes (conventional milling, debranning process, production of aleurone-rich fractions from coarse bran). By calculation of the composition of the different products generated, it was possible to study the distribution of the different tissues among fractions resulting from the different fractionation processes. This quantitative method is thus a useful tool for the monitoring and improvement of processes, and allows the effects of these processes to be understood and their adaption to reach the objectives.     

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).     

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Hydration,polymerization and rheological properties of frozen gluten-water dough as influenced by thermostable ice structuring protein extract from Chinese privet (Ligustrum vulgare) leaves

The effects of thermostable ice structuring proteins (TSISPs) extracted from Chinese privet (Ligustrum vulgare) leaves on water molecular state, dehydration of gluten proteins, secondary structure of proteins, glutenin subunit of glutenin macropolymer (GMP) and rheological properties of gluten doughs during frozen storage were investigated by nuclear magnetic resonance (NMR), attenuated total reflectance-Fourier transform infrared reflectance (ATR-FTIR), reversed phase-high performance liquid chromatography (RP-HPLC) and dynamic rheometry. After frozen storage for 5 weeks, the control sample showed dehydration of gluten proteins and mobility of water molecules in gluten dough increased, significantly indicating ice formation and water redistribution. Secondary structure of gluten proteins changed significantly, α-helix decreased and β-sheet increased. Glutenin subunits depolymerized, indicated by the decrease in high molecular weight glutenins/low molecular weight-glutenins (HMW/LMW) ratio. The decrease in elastic moduli (G′) and viscous moduli (G′') showed the deterioration of rheological properties of gluten dough. The addition of TSISPs inhibited the dehydration of gluten proteins, decrease in α-helix, increase in β-sheet and HMW/LMW ratio, resulting in improved rheological properties of gluten dough.     

Changes in the thermal and structural properties of maize starch during nixtamalization and tortilla-making processes as affected by grain hardness

The objective of this work was to evaluate the changes in the thermal and structural properties of maize starch during nixtamalization and the tortilla-making process and their relationship with grain hardness. Three maize types with varying hardness (hard, intermediate, soft) were processed by three nixtamalization processes (classic, traditional and ecological). Starch from the three maize types showed an A-type pattern and two endotherms corresponding to gelatinization and melting of the Type I amylose-lipid complexes. After cooking and steeping, in intermediate and soft grains the partial gelatinization and the annealing affected the starch properties and promoted the formation of amylose-lipid complexes. These effects were not observe in hard grains. The increase in melting enthalpy and the intensity of the peak 2θ∼20° from nixtamal to tortillas demonstrated the formation of amylose-lipid complexes. A third endotherm above 114 °C in some treatments of nixtamal and tortilla starch demonstrated the transformation of some amylose-lipid complexes in a most ordered structures (Type II complexes). The V-type polymorph structure found in native starch, nixtamal, and tortilla corresponds to a coexistence of Type I and Type II complexes. Formation of amylose-lipid complexes in tortillas had a partial effect on decreasing starch retrogradation (r = −0.47, P < 0.05).     

Impact of lipases with different substrate specificity in wheat flour separation on the properties of the resultant gluten

Wheat gluten was isolated in a laboratory dough-batter flour separation process in the presence or absence of lipases differing in hydrolysis specificity. The obtained gluten was blended with wheat starch to obtain gluten-starch (GS) blends of which the water and oil binding capacities were investigated. Furthermore, GS blends were mixed into dough and processed into model breads, of which dough extensibility and loaf volume were measured, respectively. In comparison to GS blends prepared with control gluten, oil binding capacity was higher when GS blends contained gluten isolated with Lecitase Ultra (at 5.0 mg enzyme protein/kg flour), a lipase hydrolyzing both non-polar and polar lipids. Additionally, dough extensibility and total work needed for fracture were lower for dough prepared from GS blends containing gluten isolated with Lipolase (at 5.0 mg enzyme protein/kg flour), a lipase selectively degrading non-polar lipids. In GS blend bread making, this resulted in inferior loaf volumes. Comparable GS blend properties were measured when using control gluten and gluten isolated with YieldMAX, a lipase mainly degrading N-acyl phosphatidylethanolamine. In conclusion, properties of GS blend model systems are altered when gluten prepared in the presence of lipases is used to a degree which depends on lipase specificity and concentration.     

Molecular characterization of storage proteins for selected durum wheat varieties grown in different environments

The variations of the amounts of individual high molecular weight glutenin subunits (HMW-GS), of the ratios HMW-GSy to HMW-GSx and HMW-GS to low molecular weight glutenin subunits (LMW-GS) and of protein content were evaluated for eight durum wheat cultivars in two regions using four fertilizer combinations during two successive years. All measured parameters showed significant variation with genotypes (G), environments (E) and fertilizers (F). The interaction E × G × F was highly significant for glutenin amount variation. Amongst cultivars possessing HMW-GS 20, landraces seem to better value the N-fertilizer use for the accumulation of HMW-GSy than high yielding cultivars. Both HMW-GSy to HMW-GSx and HMW-GS to LMW-GS ratios were found to be positively correlated (p < 0.05) with total protein content.     

Immunomodulatory activities of non-prolamin proteins in wheat germ and gluten

Albumin (Alb), globulin (Glo), glutelin (Gll) and glutenin (Gln) were separately extracted from wheat germ and wheat gluten. Amino acisd composition, molecular weight distribution, solubility, in vitro digestibility, and immunomodulatory activities were all analyzed. Gll and Gln have similar molecular weight distributions, which differed from those of Alb and Glo. Alb showed the highest solubility at various pH values (except pH 4.0), whereas Glo showed the highest in vitro digestibility. Glo and Gll have the highest proportion of essential to total amino acids, while Alb and Gll have the highest protein digestibility-corrected amino acid scores. Gll had the strongest immunomodulatory effects in terms of stimulation of RAW 264.7 cells to produce IL-6, TNF-α, and IL-10, and good stimulatory effects on splenocyte proliferation, production of IL-2, phagocytosis, and secretion of nitric oxide in RAW 264.7 cells. Gll can be considered a good protein source for use in health foods.