Effect of Different Wheat Classes and Their Flour Milling Streams on Textural Properties of Flour Tortillas

Wheat flour tortillas were made from flour streams of three wheat cultivars: Jagger hard red winter wheat, 4AT-9900 hard white winter wheat, and Ernie soft red winter wheat. Wheat samples were milled on a Miag experimental mill. Twelve flour streams and one straight-grade flour were obtained. Tortillas were made from each flour stream and the straightgrade flour by the hot-press method. Tortilla stretchability and foldability were evaluated by a texture analyzer and six panelists, respectively. Flour protein and water absorption affected tortilla texture. The foldability evaluated by panelists was positively correlated with flour protein content, farinograph water absorption, and damaged starch (P < 0.05). The 2BK and 3BK streams of hard wheat produced tortillas with strong stretchability and good foldability. Middling streams of hard wheat yielded tortillas with lighter color and less stretchability. Under the conditions tested in this study, soft wheat flours were not good for producing flour tortillas.     

Stability of Vitamin E in Wheat Flour and Whole Wheat Flour During Storage

The stability of vitamin E during 297 days of storage of wheat flour and whole wheat flour ground on a stone mill or a roller mill, respectively, were studied. One day after milling, the total content of vitamin E, expressed in vitamin E equivalents (α‐TE), was 18.7 α‐TE and 10.8 α‐TE for stone‐milled and roller‐milled wheat flour, respectively. The difference in total vitamin E content was primarily due to the absence of the germ and bran fractions in the roller‐milled flour. The total loss of vitamin E during storage was 24% for stone‐milled wheat flour but 50% for roller‐milled wheat flour. These results indicate that vitamin E, which is present in high amounts in wheat germ, functions as an antioxidant in the stone‐milled wheat flour. Hexanal formation showed that lipid oxidation in roller‐milled flour occurred just after milling, whereas the formation of hexanal in the germ fraction displayed a lack period of 22 days, confirming that vitamin E functions as an effective antioxidant in the wheat germ. Results showed no significant difference in total loss of vitamin E for stone‐milled and roller‐milled whole wheat flour. Total loss after 297 days of storage for both milling methods was ≈32%.     

Wheat Proteins Extracted from Flour and Batter with Aqueous Ethanol at Subambient Temperatures

Contact of wheat flour with aqueous ethanol may enrich protein by starch displacement or deplete protein by extraction depending on 1) extraction conditions and 2) the form of the substrate. Extraction at subambient temperatures has not been described for specific gliadins for either dry flour with the protein in native configurations or for wet, developed batter or dough. This limits the ability to interpret technologies such as the cold-ethanol method. Here, we describe specific albumin and gliadin composition of flour extracts by capillary zone electrophoresis CZE in 0–100% (v/v) ethanol from –12 to 22°C. Extraction was reduced for albumin and gliadin protein as the temperature was reduced and the concentration range for extraction narrowed. Extraction dropped precipitously between 0 and –7°C for both albumins and gliadins. Electrophoretically defined gliadins extracted in constant proportion at 22°C and 30–80%(v/v) ethanol, but at lower temperature, the α-gliadins were enriched and β-gliadins depleted in the 30–55% (v/v) range. For extracts from wheat flour batter, depletion of α and β and enrichment of γ relative to the dry flour contact suggested that the electrophoretically slow migrating γ- and ω-proteins are less well incorporated to the dough matrix than electrophoretically fast migrating α and β types.     

Storage of Wheat Grains at Elevated Temperatures Increases Solubilization of Glutenin Subunits

Grains of two wheat (Triticum aestivum L.) cultivars, Sunco and Sunsoft, were stored at 4°C and 30°C for 270 days to examine changes in proteins during storage. When whole meal flour extracted from the grains was analyzed using an unfractionated protein extraction procedure, no significant changes were found in protein content or SDS‐PAGE profile for either cultivar in samples stored at 30°C compared with those stored at 4°C. Fractionation of the flour samples from stored grain into soluble and insoluble proteins revealed increases in soluble protein content for both cultivars stored at 30°C compared with 4°C. The soluble protein content, expressed as a percentage of the total protein, increased by 1.5% (P = 0.032) for Sunco and by 8.0 % (P = 0.158) for Sunsoft during storage at 30°C compared with those samples stored at 4°C. Analysis by SDS‐PAGE and subsequent protein identification revealed that the most evident change that occurred during storage at 30°C was an increase in the content of high molecular weight glutenin subunits (HMW‐GS) in the soluble fraction. The potential effect of changes in solubility of HMW‐GS on functional properties is discussed.     

不同温度条件下沙棘雄株花粉储存时间研究

为研究不同温度条件、不同储存时间对沙棘雄株花粉生活力的影响,采用蓝墨水染色法对分别保存在20～22℃室温和4℃低温条件下的沙棘雄株花粉离体后的生活力进行了测定。结果表明:室温下无刺雄花粉存活时间最短,活性下降速度最快,离体5～11 d下降速度达到峰值,中雄花粉存活时间最长,活性下降速度最慢,11～15 d下降速度到达峰值,以花粉生活力50%为下限,阿列伊与201306可以存活9 d,中雄可以存活11 d,无刺雄存活7 d;4℃低温条件下,阿列伊花粉存活时间最长,为17 d,活性下降速度最慢,在离体15～21 d时下降速度达到峰值,无刺雄花粉存活时间最短,为9 d,活性下降速度快,在5～11 d时下降速度达到峰值,中雄与201306花粉存活时间分别为13、11 d。     

Characterization of Dynamic Viscoelastic Behavior of Wheat Flour Doughs at Different Moisture Contents

Three different flours were examined to study the influence of moisture content on the dynamic viscoelastic behavior of wheat flour dough. Doughs with moisture contents varying from 43 to 58% were submitted to dynamic testing using a mechanical spectrometer operating in frequency sweep mode, obtaining information about rheological response in the linear viscoelastic range. To characterize the influence of moisture content on the dynamic viscoelastic behavior of wheat flour dough, some hypotheses regarding the functional role of the water molecules were verified by applying reduction procedures of the rheological curves. By shifting the rheological curves along the vertical axis, it was possible to verify that varying the moisture content of the doughs not only changed dynamic properties but also modified viscoelastic response. By applying a reduction procedure similar to that used to estimate the constants of the Williams, Landel, and Ferry equation, we demonstrated that not only did the viscoelastic response of doughs vary, but that water molecules interfere with the dynamic by which relaxation phenomena take place. Finally, we proved that the rheological behavior of flour dough is similar to that of concentrated polymer solutions, and that it can be characterized by using a double reduction procedure, shifting the rheological curves along the vertical and horizontal axes, and obtaining a master curve that can be considered inherently characteristic of viscoelastic behavior.     

Alkylation of Free Thiol Groups During Extraction: Effects on the Osborne Fractions of Wheat Flour

Wheat proteins are classified according to solubility into the so‐called Osborne fractions. Because wheat flour contains both free thiol and disulfide groups, thiol–disulfide interchange reactions are possible during extraction. Osborne fractionation of 12 different wheat flour samples was performed in the presence of N‐ethylmaleinimide (NEMI) to alkylate free thiol groups and without addition of NEMI (control). The addition of NEMI during extraction tended to decrease the content of gliadins (predominantly α‐gliadins) and caused an increase of the content of glutenins in most flour samples. Thus, alkylation of free thiol groups during extraction led to a decline of the gliadin/glutenin ratio from 2 (control) to approximately 1.5 (NEMI). NEMI and control gliadins were separated by gel‐permeation HPLC into an oligomeric subfraction (high‐molecular‐weight [HMW] gliadins) and two monomeric subfractions. In most flours (8 of 12), the addition of NEMI led to a significant increase of the content of HMW gliadins. HMW gliadins from cultivar Akteur wheat were preparatively isolated from NEMI and control gliadins and characterized by HPLC, sodium dodecyl sulfate polyacrylamide gel electrophoresis, and N‐terminal sequencing. HMW gliadin isolated in the presence of NEMI had a significantly higher content of low‐molecular‐weight glutenin subunits and disulfide‐bound cysteine as well as a lower content of α‐gliadins and disulfide‐bound glutathione compared with the control.     

Effect of Storage on Fat Acidity and Pasting Characteristics of Wheat Flour

Two cultivars of wheat (Triticum aestivum L.), Sunco and Sunsoft, were used to study the influence of storage time and temperature on the formation of starch-lipid complexes in flour pastes. Untreated and fat-reduced whole meal flours were stored separately for up to 12 months at 4, 20, and 30°C. The stored samples were analyzed for fat acidity, pasting properties, and iodine binding values. Fat acidity increased significantly in the untreated flour samples stored at 30 and 20°C compared with 4°C. Starch pasting properties, as measured using a Rapid Visco Analyser (RVA) indicated that the final viscosity of untreated flour samples of both cultivars increased significantly with storage time and elevated temperature, and correlated positively with increased fat acidity. Iodine binding values of the RVA pastes decreased with storage time and elevated temperature, and correlated negatively with fat acidity and final viscosity. The fat-reduced Sunco and Sunsoft flours showed less pronounced changes compared with untreated flours, whereas small changes in the RVA parameters were noted in grains stored over 12 months. The results indicate that free fatty acids are released during storage and that they increase the potential for starch-lipid complex formation when stored whole meal wheat flours are pasted in the RVA. These changes were evident after two to three months of storage at 20 and 30°C.     

不同热解温度制备的水稻秸秆生物炭理化特性分析

以不同热解温度(100～800℃)制备的水稻秸秆生物炭为研究对象,研究在不同热解温度下制成的生物炭的理化特性。结果表明,热解温度为100～300℃制成的水稻秸秆生物炭呈弱酸性,400℃以上时呈碱性;水稻秸秆生物炭表面碱性含氧官能团数量随着热解温度的升高而增加、酸性含氧官能团则减少;水稻秸秆生物炭中的官能团C=C、C-O-C、-OH和-C=O在较高的热解温度下发生缔合或消除,促进了芳香基团的形成;随着热解温度的升高,水稻秸秆生物炭的阳离子交换量(CEC)、比表面积、孔径、比孔容、氮气吸附量和颗粒表面的分型维数(D1)均先增加后降低,阳离子交换量(CEC)在300～500℃时、其它性状在400～600℃之间达到最大值;以不同热解温度制成的水稻秸秆生物炭颗粒的孔隙结构均以孔隙宽度2～50 nm的中孔为主。随热解温度的升高,水稻秸秆生物炭的产率逐渐降低;400～500℃炭化2 h,生物炭产率最高,其孔隙结构最为复杂,所以可以认为400～500℃是水稻秸秆炭化的最佳温度。     

Effect of Puroindolines on the Breadmaking Properties of Wheat Flour

The role of lipid-binding proteins from wheat seed (puroindolines) on the breadmaking properties of wheat flour was investigated by determining the relationship between breadmaking quality and puroindoline content in samples of 32 wheat cultivars. An inverse relationship was mainly explained by the link between hardness and puroindoline contents. This link is in agreement with previous results which have shown a close structural identity between basic friabilins and puroindolines. Next, the effect of puroindolines in breadmaking was investigated by performing reconstitution experiments with two puroindoline-free hard cultivars of opposite quality (Florence Aurore and Ecrin) as indicated in the screened wheat sample. Addition of 0.1% puroindolines to these flours drastically modified both the rheological properties of doughs and the structure of the bread crumb. Puroindolines are essential to the foaming properties of dough liquor, and a close relationship was found between the fine grain crumb provided by reconstituted flours with puroindolines and the fine structure of corresponding dough liquor foams. The effect of puroindolines on bread volume was mainly related to the rheological properties of wheat doughs.     

Granule Bound Starch Synthase I (GBSSI) Gene Effects Related to Soft Wheat Flour/Starch Characteristics and Properties

Eight soft spring wheat (Triticum aestivum L.) genotypes representing the four granule bound starch synthase I (GBSSI) classes were evaluated with respect to flour/starch characteristics and pasting behaviors. Native starch was isolated from genotype straight‐grade flours (94.8–98.1% of starch recovered) to approximate the starch populations of the parent flours. As anticipated, amylose characteristics varied among the genotypes according to GBSSI class and accounted for the primary compositional difference between genotypes. Total (TAM), apparent (AAM), and lipid‐complexed (LAM) amylose contents ranged from 1.0–25.5 g, 0.7–20.4 g, and 0.3–5.6 g/100 g of native starch, respectively, and gradually decreased with the progressive loss of active Wx alleles. In addition, genotype flour total starch (FTS) and A‐type starch granule contents, which ranged from 81.7–87.6 g/100 g of flour (db) and 61.6–76.8 g/100 g of native starch (db), respectively, generally decreased with an increase in waxy character in parallel with amylose characteristics, as likely secondary effects of Wx gene dosage. Though amylose characteristics predominantly accounted for the majority of genotype flour pasting properties, FTS content and ratios of A‐ to B‐type granules also exhibited significant influence. Thus, loss of one or more Wx genes appeared to induce measurable secondary effects on starch characteristics and properties.     

Characteristics of Perennial Wheatgrass (Thinopyrum intermedium) and Refined Wheat Flour Blends: Impact on Rheological Properties

Intermediate wheatgrass (IWG) (Thinopyrum intermedium) is a perennial grass with desirable agronomic traits and positive effects on the environment. It has high fiber and protein contents, which increase the interest in using IWG for human consumption. In this study, IWG flour was blended with refined wheat at four IWG‐to‐wheat ratios (0:100, 50:50, 75:25, and 100:0). Samples were analyzed for proximate composition, microstructure features, pasting properties (Micro Visco‐Amylo‐Graph device), protein solubility, and total and accessible thiols. Gluten aggregation properties (GlutoPeak tester) and mixing profile (Farinograph‐AT device) were also evaluated. IWG flour enrichment increased the pasting temperature and decreased the peak viscosity of blended flours. IWG proteins exhibited higher solubility than wheat, with a high amount of accessible and total thiols. The GlutoPeak tester highlighted the ability of IWG proteins to aggregate and generate torque. Higher IWG flour enrichment resulted in faster gluten aggregation with lower peak torque, suggesting weakening of wheat gluten strength. Finally, the addition of IWG to refined wheat flour resulted in a decrease in dough development time and an increase in consistency, likely because of the higher levels of fiber in IWG. The 50% IWG flour enrichment represents a good compromise between nutritional improvement and maintenance of the pasting properties, protein characteristics, and gluten aggregation kinetics.     

Rheological and Sensory Evaluation of Wheat Flour Tortillas During Storage

Texture of wheat flour tortillas over 15 days at room temperature was evaluated using an expert sensory panel, consumer panels, subjective rollability test, large deformation rheological methods (i.e., bending, extensibility [1‐D and 2‐D], and puncture tests), and stress relaxation method. Most of the changes in texture occurred during the initial 8 days of storage, while texture of tortillas changed slowly thereafter. Differences in texture between fresh and 1‐day‐old tortillas were detected by many objective rheological methods but not by either sensory panel. The expert sensory panel observed a rapid decrease in tortilla extensibility and an increase in staleness between 1 and 8 days of storage and smaller changes in sensory scores after 8 days of storage. Most objective rheological parameters changed rapidly between 0 and 5 days, and slowly after 5 days of storage. Significant correlations and factor analysis reveal that changes occurring in flour tortillas during staling are estimated better by subjective rollability, sensory evaluation (expert and consumer panels), and 2‐dimensional extensibility test than by other methods. Hence, some rheological methods are useful to estimate sensory properties of flour tortillas.     

Effects of Wheat Protein Fractions on Flour Tortilla Quality

Commercial wheat protein fractions (10) were evaluated during processing for quality of tortillas prepared using pastry, tortilla, and bread flours. Protein fractions that separately modify dough resistance and extensibility were evaluated in tortillas to determine whether the proteins could increase diameter, opacity, and shelf stability. Tortillas were prepared using laboratory‐scale, commercial equipment with fixed processing parameters. Dough and tortilla properties were evaluated using analytical methods, a texture analyzer, and subjective methods. Tortillas were stored in plastic bags at 22°C for up to 20 days. Adjustments in water absorption and level of reducing agent were made to normalize differences in functionality of 3% added proteins on dough properties. Tortilla weight, moisture, pH, opacity, and specific volume were not affected by added proteins, except for glutenin and vital wheat gluten treatments, which had decreased opacity in tortillas prepared from pastry flour. Increased insoluble polymeric protein content corresponded to decreased tortilla diameter and improved shelf stability. Treatments yielding tortillas with improved shelf stability and similar tortilla properties were produced when commercially processed vital wheat gluten products, FP600, FP6000, FP5000, or gliadin were added to pastry or tortilla flour. These wheat protein fractions improved processing and tortilla quality of wheat flours, especially pastry flour, by modifying protein content and quality.     

Effect of Flour Extraction Rate on White and Red Winter Wheat Flour Compositions and Tortilla Texture

Wheat flours commercially produced at 74, 80, and 100% extraction rates made from hard white winter wheat (WWF) and hard red winter wheat (WRF) were used to produce tortillas at a commercial-scale level. Flour characteristics for moisture, dry gluten, protein, ash, sedimentation volume, falling number, starch damage, and particle-size distribution were obtained. Farinograms and alveograms were also obtained for flour-water dough. A typical northern Mexican formula was used in the laboratory to test the tortilla-making properties of the flours. Then commercial-scale tortilla-baking trials were run on each flour. The baked tortillas were stored at room and refrigeration temperatures for 0, 1, 2, and 3 days. Maximum stress and rollability were measured every day. Tortilla moisture, color, diameter, weight, and thickness were measured for each treatment. Finally, tortilla acceptability was tested by an untrained sensory panel. Analyses of variance (ANOVA) were performed on the data. WWF had higher protein content, dry gluten, sedimentation volume, and water absorption than the WRF. The WWF was the strongest flour based on farinograph development time and alveograph deformation work. It also produced the most extensible dough measured with the alveograph (P/L). Flour protein and ash contents, water absorption, and tenacity increased directly with the flour extraction rate. Both WWF and WRF performed well in commercial-scale baking trials of tortillas. Tortillas made with both types of flours at 74 and 80% extraction rates had the best firmness and rollability. However, tortillas made with WWF 80% had the best color (highest L value). Tortillas prepared with 100% extraction rate flour were also well accepted by the sensory panel, had good textural characteristics, and became only slightly firm and slightly less rollable after three days of storage at room temperature.     

Effects of Laccase and Ferulic Acid on Wheat Flour Doughs

The effects of a laccase from the fungus Pycnoporus cinnabarinus on the mixing of a wheat flour dough with or without added ferulic acid (FA) were studied. Laccase reduced dough time‐to‐peak and accelerated dough breakdown in comparison with the control. Its effect was enhanced with FA. The water extractability of arabinoxylans (AX) increased during mixing of a dough free of added laccase, especially with exogenous FA. At the same time, the extractability of FA decreased during mixing. Added FA may have competed with endogenous AX feruloyl esters, inhibiting partly oxidative gelation. Laccase decreased AX extractability by chain cross‐linking through oxidative dimerization of feruloyl esters. FA and, moreover, FA plus laccase, increased the oxidation of sulfhydryl (SH) groups. FA and, even more, FA in combination with laccase, increased the rate of protein depolymerization during mixing. FA and the products of FA laccase oxidation participated in a redox reaction involving SH groups. A coupling reaction involving enzymatically generated feruloyl radicals and thiol radicals generated through the mechanical breakdown of inter‐chain disulfide bonds might explain these results.     

Effects of Added Minerals on Pasting of Partial Waxy Wheat Flour and Starch and on Noodle Making Properties

Mineral content, as determined and expressed by ash content, serves as an index of wheat flour quality for flour millers and food manufacturers who prefer flour of low mineral content, even though the significance of mineral content on the functional properties of wheat flour is not well understood. We explored whether minerals have any influence on the functional properties of wheat flour and product quality of white salted noodles. Ash, obtained by incinerating wheat bran, was incorporated into two hard white spring wheat flours and their starches to raise the total ash content to 1, 1.5, or 2%. Pasting properties were determined using a rapid visco analyzer (RVA). Addition of ash increased the peak viscosity of the flours in both water and buffer solution but did not affect the peak viscosity of starch. Wheat flours with added ash showed lower pasting temperature by approximately 10°C in buffer solution. Mineral extracts (15.3% ash) isolated from wheat bran, when added to increase the ash content of wheat flour and starch to 2%, increased the peak viscosity and lowered the pasting temperature of flour by 13.2–16.3% but did not affect the pasting properties of the isolated starch. The mineral premix also increased peak viscosity of wheat flour but not in starch. Added ash increased noodle thickness and lowered water retention of cooked noodles while it exhibited no significant effect on cooked noodle texture as determined using a texture analyzer.     

Effects of Prolonged Storage at Freezing Temperatures on Starch and Baking Quality of Frozen Doughs

The effects of prolonged frozen storage on the starch, rheological, and baking properties of doughs were investigated. Four hard red spring (HRS) wheat cultivars exhibiting consistently different gluten characteristics were used. Gelatinization properties of starches isolated from fresh and thawed frozen doughs over 16 weeks of frozen storage were examined using differential scanning calorimetry (DSC). Significance of results varied with cultivar, but all cultivars showed a significant increase in ΔH with increased frozen storage time, indicating water migration and ice crystallization. The amount of freezable water in frozen doughs increased for all cultivars with frozen storage, but the rate of increase varied. Glupro showed a consistent increase in freezable water during frozen storage (41.6%), which may be associated with its high protein content and strong gluten characteristics. Rheological strength of the frozen doughs which was determined by decreases in extensigraph resistance and storage modulus (G′), declined throughout frozen dough storage. Proofing time increased from 45 min for fresh doughs to an average of 342 min for frozen doughs stored 16 weeks. Concomitantly, loaf volumes decreased from an average of 912 cm³ for fresh doughs to an average of 738 cm³ for the frozen doughs. Longer proof times and greater loaf volume loss were obtained for the cultivars exhibiting greater gluten strength characteristics.     

Effect of Ultrasonic Treatment of Brown Rice at Different Temperatures on Cooking Properties and Quality

This research studied developing quick cooking brown rice by investigating the effect of ultrasonic treatment at different temperatures on cooking time and quality. The medium grain brown rice was ultrasonically treated in water at temperatures of 25, 40, and 55°C for 30 min and then dried by air at 25°C to its initial moisture content (11.0 ± 0.6%, wb) before cooking. The microstructure of rice kernel surface, chemical composition, and optimal cooking time of treated brown rice were determined. The pasting and thermal properties and chemical structure of flour and starch from treated brown rice were also examined. The results showed that the optimal cooking times were 37, 35, and 33 min after treatment at 25, 40, and 55°C, respectively, compared to the control of 39.6 min. The ultrasonic treatment resulted in a loss in natural morphology of rice bran, allowing water to be absorbed by a rice kernel easily, particularly at high‐temperature treatment. Even through rice flour still maintained an A‐pattern in the pasting properties, the crystallinity significantly increased after treatment at 55°C. Ultrasonic treatment increased the peak, hold, and final viscosities and decreased the onset temperature (T_o) and peak temperature (T_p), significantly. Thus, ultrasonic treatment could be used for reducing cooking time of brown rice.     

Properties and Composition of Turkish Flat Bread (Bazlama) Supplemented with Barley Flour and Wheat Bran

In this study, effects of increasing levels of wheat bran and barley flour on dough properties and bazlama quality were investigated. Bazlama is a flat bread commonly consumed in Turkey. Flours of wheat cultivars Gün and Gerek, flour of barley cultivar Tokak, and Gerek bran mixture were used. Part of the wheat flours were replaced with barley flour at 10, 20, 30, and 40% levels and Gerek bran mixture at 5, 10, 15, and 20% levels. Farinogram properties of mixtures were determined. Bazlama samples were subjected to sensory analysis for external appearance, shape and symmetry, crust color, crumb color and structure, mouthfeel, taste and aroma. Increasing levels of bran and barley flour caused decreases in all sensory properties. The deteriorative effect of barley flour on bazlama properties was generally more obvious when compared to bran supplementation. However, all bazlama samples were considered acceptable. Penetrometer values of bazlama samples showed that increasing levels of barley flour created significantly softer bazlama. However, in bran-supplemented bazlama samples, effect of bran on softness was found to be insignificant in both cultivars. Bazlama samples supplemented with bran had lower L values and higher a and b values for color when compared to those supplemented with barley flour. In all samples, effect of increasing levels of barley flour on residual β-glucan was found to be insignificant in both cultivars. Acid detergent fiber and neutral detergent fiber values increased with increasing levels of bran, and the changes in both cultivars were similar.