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1.
Gluten was isolated from three durum wheat cultivars with a range in strength. Gluten was further fractionated to yield gliadin, glutenin and high molecular weight (HMW) and low molecular weight (LMW) glutenin subunits (GS). The gluten and various fractions were used to enrich a base semolina. Enriched dough samples were prepared at a fixed protein content using a 2‐g micromixograph. Mixing strength increased with addition of gluten. Dynamic and creep compliance responses of doughs enriched with added gluten ranked in order according to the strength of the gluten source. Gliadin addition to dough resulted in weaker mixing curves. Gliadin was unable to form a network structure, having essentially no effect on dough compliance, but it did demonstrate its contribution to the viscous nature of dough (increased tan δ). Source of the gliadin made no difference in response of moduli or compliance. Addition of glutenin to the base semolina increased the overall dough strength properties. Glutenin source did influence both dynamic and compliance results, indicating there were qualitative differences in glutenin among the three cultivars. Enrichment with both HMW‐GS and LMW‐GS increased overall dough strength. Source of HMW‐GS did not affect compliance results; source of LMW‐GS, however, did have an effect. The LMW‐2 proteins strengthened dough to a greater extent than did LMW‐1. Mechanisms responsible for dough viscoelastic properties are described in terms of reversible physical cross‐links.  相似文献   

2.
A modified extensigraph method reduced sample quantity to 100 g from 300 g and testing time by half with easy dough preparation compared to the AACC standard extensigraph method, which challenges wheat breeding programs where the sample size is small and evaluations of large numbers of samples are demanded. Correlation coefficients (r) for 93 pairs of each of six extensigraph dough characteristics of 31 different tested wheat samples were r = 0.95 for resistance‐to‐extension, r = 0.80 for extensibility, r = 0.93 for ratio of resistance‐to‐extension to extensibility, r = 0.92 for ratio of maximum resistance‐to‐extension to extensibility, and r = 0.81 for area under the curve (energy). Correlation coefficients for the measurements of extensigraph dough characteristics at each of three rest‐time tests between the modified and standard methods were significant. Some dough mixing characteristics and bake tests correlated better with dough extension characteristics when determined by the modified method. Repeatability of the modified method test was good. The modified extensigraph method can be a useful alternative to the standard method for the milling and baking industries, crop quality surveys, and wheat quality research.  相似文献   

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Durum wheat gluten strength is important in determining extrusion properties and pasta cooking quality. Durum wheats varying in strength were tested using an alveograph and a 2-g micro-mixograph, both widely accepted techniques for determination of physical dough properties. Doughs from the 2-g micro-mixograph were characterized by dynamic oscillatory and large deformation creep tests using a controlled stress rheometer. Mechanical properties obtained from both testing regimes were strongly correlated with many of the parameters provided by the alveograph and micro-mixograph. Maximum strain attained after 5 min creep ranged from <5% for the strongest least extensible cultivar to >25% for the weakest cultivar, with a coefficient of variation among replicates of <10%. Storage modulus (G′) at 2 Hz ranged from ≈7,000 Pa for the weakest cultivar to >16,000 Pa for the strongest, least extensible cultivars, with a coefficient of variation of <6%. Tan δ (G″/G′) values were ≈0.4 for the strongest versus >0.5 for the weakest cultivars, indicating the larger contribution of the elastic component in the strong cultivars. The rheometer allows discrimination of durum wheat cultivars of varying gluten strength while requiring less sample than traditional physical dough testing techniques.  相似文献   

5.
The contribution of starch to dough rheological properties has been largely overshadowed by the role of gluten, receiving much less attention in comparison. The influence of starch granule surface properties on durum wheat dough linear viscoelasticity was investigated, and surface interactions between starch granules and gluten were assessed using a model system. Proportions of starch were substituted in dough on a volume basis with an inert filler (glass powder) with a similar particle size range. The doughs were subjected to dynamic and creep measurements. Dough linear viscoelastic properties were weakened on substitution of starch with glass powder at ≤50% substitution, inferring a reduction in adhesion at the matrix‐filler (starch and glass powder) interface with declining proportions of starch granules. Surface modification of starch granules or glass powder altered dough rheological properties, confirming the importance of starch granule surface characteristics and the nature of protein‐starch bonding on durum dough linear viscoelastic behavior.  相似文献   

6.
Ten durum wheat cultivars harvested in Manitoba in 1995, which were downgraded primarily because of fusarium-damaged (FD) kernels, were subjected to mycological tests and evaluated for semolina milling and pasta-making quality. Fusarium graminearum was the primary fungus infecting kernels. The ratio of FD to deoxynivlaenol (DON) level varied slightly among cultivars but was generally near unity. Retention of DON in semolina was about 50%. FD had a negative impact on kernel weight and test weight, resulting in lower semolina yield. Semolina ash content and bran specks were not affected by FD, but semolina became duller and redder. FD had no effect on protein content, but gluten strength was weaker probably due to a lower proportion of glutenins as shown by reversed-phase high-performance liquid chromatographic analysis of sequentially extracted gluten proteins. The influence of FD on gluten strength was not sufficient to alter pasta texture. FD had a strong adverse effect on pasta color. Even for the least damaged cultivars, which had FD levels near the limit of 2% established for the No. 3 and No. 4 Canadian Western Amber Durum (CWAD) grades, the deterioration in pasta color was readily discernible by eye, confirming that the strict FD tolerances for premium No. 1 CWAD (0.25%) and No. 2 CWAD (0.5%) grades are warranted.  相似文献   

7.
Proton high‐resolution magic angle spinning nuclear magnetic resonance (1H HR‐MAS NMR) has been applied for the analysis of two cultivars of durum wheat produced in different Italian geographical areas. Furthermore, on the same samples, isotopic ratios were measured by mass spectrometry (IRMS). The application of chemometrics to these results permitted the discrimination of semolina by cultivar and geographical origin. A similar approach has been applied to the results obtained from chemical analyses. The comparison showed that NMR spectroscopy can provide a faster method for the detection of differences among the durum wheat semolina according to geographical and varietal origin. Furthermore, IRMS data are suitable to provide information about the geographical origin of samples. This present investigation is part of an extensive research project to find a scientific method capable of classifying wheat foods for the assignment of a “denomination of origin” trademark.  相似文献   

8.
A rapid shear‐based test (the GlutoPeak test, recently proposed by Brabender) was used to investigate gluten aggregation properties of durum wheat semolina and to relate them to pasta cooking behavior. Thirty semolina samples were characterized by means of the conventional approaches used for pasta‐quality prediction (protein content, gluten index, and alveographic indices). All samples were also analyzed by the GlutoPeak test, obtaining three parameters: maximum peak torque, maximum peak time, and area under the peak. The GlutoPeak indices were significantly correlated with protein content, gluten index, and W alveographic parameter. The cooking quality of pasta obtained from the 30 semolina samples was evaluated by sensory analysis in terms of stickiness, bulkiness, firmness, and overall quality. The GlutoPeak indices were significantly correlated with the sensorial parameters. In comparison with the alveographic test, which is presently the most used rheological approach for semolina characterization, GlutoPeak analysis presents some advantages represented by a smaller amount of sample (9 g), a shorter time (less than 5 min), and the possibility that untrained analysts can carry it out. In addition, following testing with larger sample numbers, the GlutoPeak test has the potential to be used instead of the gluten index as a rapid and reliable approach for medium‐quality semolina characterization.  相似文献   

9.
During pasta making, semolina is subject to various modifications that are mainly related to oxidative activities with relative effects on some of its components. To evaluate the involvement of hydroperoxidation and bleaching of lipoxygenase (LOX) and peroxidase (POD) activities on loss of pigments and ‐SH groups, their behavior in semolina and during processing was analyzed. Processing was done in standard and four experimental conditions, applying chemical (pH 5.0 and 8.0) and physical (10 and 40°C) treatments, during the mixing and extrusion phases, to study their effects on components. Results pointed out that treatments principally affected hydroperoxidation and bleaching activities of LOX rather than the POD. During pasta making, enzymatic activities showed the same trend in all cultivars, and this was reproducible in all the experimental conditions. Temperature effects on preservation of components were modest, whereas pH 8.0 improved the residual pigment and ‐SH group content in pasta, probably because of the concomitant reduction of oxidative enzyme levels. Finally, out of the four investigated wheat cultivars, Cosmodur showed the best performance in the experimental conditions applied. In fact, high pigment content and yellow index associated with low oxidative activity levels in semolina and in processing samples resulted in better pasta color. Such findings have confirmed that breeding and technological approaches may play an important role in the control of oxidative activities during pasta making, preserving the constituents that positively influence the final pasta color.  相似文献   

10.
Pasta prepared by extrusion from 25 g of semolina has been compared with that made from a standard laboratory extruder and found to have similar quality. Durum semolina was fractionated into its starch, gluten, water soluble, and residue fractions. The freeze‐dried components were reconstituted and the properties of the reconstituted semolina (ReSem) have been measured. Examination using a 2 g‐mixograph and micro‐extension tester has shown that ReSem behaves similarly to the original semolina. ReSem and semolina were made into pasta using a small‐scale pasta extruder and were of comparable cooking quality. The fractionation and reconstitution of durum semolina on this scale is a useful technique to evaluate the contribution of semolina components to pasta quality.  相似文献   

11.
《Cereal Chemistry》2017,94(6):1045-1051
Durum wheat landraces have been recognized to have different contents in health‐promoting phytochemicals. These health benefits have been mainly attributed to the presence of phenolic acids and flavonoids existing in this matrix both as soluble free compounds and insoluble bound forms. Sicily is one of the few areas of Southern Europe where it is still possible to find landraces of durum wheat, no longer cropped because of the commercial spread of new high‐yielding varieties. This study aimed to determine the phenolic profile and content of 10 wheat landraces and three genetically improved cultivars to develop an analytical tool for cultivar screening and traceability. Hydroalcoholic extracts from wheat grains were analyzed by means of HPLC with a diode‐array detector and HPLC electrospray ionization MS, revealing 13 metabolites belonging mainly to the classes of hydroxycinnamic acids and flavones C‐glycosides. The quantitative pattern of the 13 phenolic markers, analyzed by applying stepwise linear discriminant analysis, allowed the discrimination between the two groups under study, namely, modern cultivars and durum wheat landraces. Furthermore, all 13 durum wheat varieties were perfectly discriminated in this statistical model, confirming a specific and genotype‐dependent pattern of phenolics concentration.  相似文献   

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13.
《Cereal Chemistry》2017,94(2):242-250
The global market for frozen bread dough is rising; however, its quality could deteriorate during extended storage. Our previous study indicated that undesirable changes caused by freezing could be reduced by adding arabinoxylan‐rich fiber sources. The present study investigated the changes in arabinoxylan properties of yeasted dough during frozen storage. Dough samples made from refined, whole, and fiber‐enriched (15% either wheat aleurone or bran) flours were stored at –18°C for nine weeks, and structural properties of arabinoxylan were probed during storage. Water‐extractable arabinoxylan (WEAX) content in dough samples increased by about 19–33% during the first three weeks of storage. Prolonged storage of dough (weeks 6 and 9), however, correlated with a decline in WEAX content. Average molecular weight and intrinsic viscosity of WEAX decreased during storage for all frozen dough samples. Arabinose‐to‐xylose ratios also decreased by 11 and 6% for control and composite dough samples, respectively. There was a significant positive correlation (r = 0.89, P < 0.0001) between WEAX content of dough and bread quality throughout the storage period. The results demonstrated that changes in dough quality during frozen storage were related to changes in the content and structure of WEAX that took place during frozen storage.  相似文献   

14.
Exposure of wheat flour to ethanol solutions followed by slow drying of the ethanol in situ alters the subsequent transformation of the flour into dough. Several types of wheat flour were exposed to small amounts of ethanol solutions so as to be “wetted” but without the appearance of a separate liquid phase. The wet sample was then dried in air. Dough was formed from the treated flour, and its rheological parameters were assessed, including time to peak strength (mixograph and farinograph) and gluten index (glutomatic). Untreated and treated flour and the dough prepared therefrom were assayed using 1D SDS‐PAGE (reducing and unreducing conditions), capillary zone electrophoresis (CZE) applied to 70% leachates with and without sonication, and differential scanning calorimetry. Both gluten index and time to peak increased as a result of the treatment, and the increase was greater for flour or enriched vital gluten with an initially low gluten index than for flour with a relatively high initial index. Endosperm fragmentation following milling of the treated flour was improved by the treatment. Thermal transitions were at lower temperatures following treatment, indicating less structural order and reduced thermal stability. No compositional differences were evident when studied with robust analytical methods. CZE of leached samples (no sonication) revealed lower amounts of accessible or detected proteins following treatment. Conformational changes and new secondary interactions, therefore, appear to cause the effect.  相似文献   

15.
Worldwide, nearly 20 times more common wheat (Triticum aestivum) is produced than durum wheat (T. turgidum subsp. durum). Durum wheat is predominately milled into coarse semolina owing to the extreme hardness of the kernels. Semolina, lacking the versatility of traditional flour, is used primarily in the production of pasta. The puroindoline genes, responsible for kernel softness in wheat, have been introduced into durum via homoeologous recombination. The objective of this study was to determine what impact the introgression of the puroindoline genes, and subsequent expression of the soft kernel phenotype, had on the milling properties and flour characteristics of durum wheat. Three grain lots of Soft Svevo and one of Soft Alzada, two soft‐kernel back‐cross derived durum varieties, were milled into flour on the modified Quadrumat Senior laboratory mill at 13, 14, and 16% temper levels. Samples of Svevo (a durum wheat and recurrent parent of Soft Svevo), Xerpha (a soft white winter wheat), and Expresso (a hard red spring wheat) were included as comparisons. Soft Svevo and Soft Alzada exhibited dramatically lower single‐kernel characterization system kernel hardness than the other samples. Soft Svevo and Soft Alzada had high break flour yields, similar to the common wheat samples, especially the soft hexaploid wheat, and markedly greater than the durum samples. Overall, Soft Svevo and Soft Alzada exhibited milling properties and flour quality comparable, if not superior, to those of common wheat.  相似文献   

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In this study, a practical spectrophotometric approach was used to determine the hydroperoxidation activity of durum wheat lipoxygenase (LOX). As stated in the related literature, the buffered linoleic acid solution used as the reaction medium is not optically clear enough at neutral and lower pH values due to its limited solubility. In our study, the optical clarity was obtained by the formation of sodium-salt of unreacted linoleic acid just before absorbance measurement. The durum wheat LOX was characterized in terms of pH and temperature optima as well as kinetic parameters. The maximum linoleic acid hydroperoxidation activities were determined at pH 5.0 and 6.5 and at 40°C This result can be considered as evidence for the presence of at least two LOX isoforms with respective optima at pH 5.0 and 6.5 in the crude durum wheat extract. The Michaelis constant (Km) and maximum hydroperoxidation) activity rate (Vmax) of durum wheat LOX for linoleic acid were estimated) to be 0.131 ± 0.019 mM and 42.37 ± 3.32 units/mg of protein/min, respectively. The method seems to be useful for the determination of LOX activity in durum wheat and its milling fractions.  相似文献   

18.
Economic losses due to suni‐bug (Eurygaster spp. and Aelia spp.) damage are important for the cereal industry in East European and Middle East countries. Samples of five durum wheat cultivars (Diyarbakir, Firat, Ege, Svevo, and Zenith) with zero, medium, and high levels of suni‐bug damage were used to determine the effects of suni‐bug damage on milling properties and semolina quality. As the damage level increased, semolina yields of all cultivars decreased significantly. The loss of semolina yield was greater than decreases in total yield of semolina plus flour, indicating that semolina yields were affected to a higher extent than were flour yields. The ash contents of the semolina samples increased significantly in all cultivars with increasing suni‐bug damage. The falling number values were not correlated with suni‐bug damage level and amylase activities of all samples were quite low. The pasting properties did not differ to a great extent depending on the suni‐bug damage level. Gluten quality of semolina samples substantially deteriorated as suni‐bug damage level increased, as determined by SDS‐sedimentation and mixograph analyses. It was concluded that suni‐bug damage would decrease profits of durum wheat millers substantially by affecting semolina yield and quality.  相似文献   

19.
Manipulation of starch composition in cereals and particularly in wheat is receiving increasing attention due to recognition of its important role in food and nonfood applications. The amylose/ amylopectin ratio influences the physicochemical properties of starches and nutritional value of derived end products. Identification of the key enzymes involved in the starch biosynthetic pathway has opened new avenues for altering the amylose and amylopectin content in durum and bread wheat. The granule bound starch synthases (GBSSI), or waxy proteins, are the enzymes responsible for amylose synthesis in storage tissues; amylopectin is produced by the concerted action of different enzymes, including starch synthases (SS), branching (SBE), and debranching enzymes (DBE). By altering the level of key enzymes involved in the regulation of starch synthesis, it is possible to generate novel starches with unique functional properties. In this respect, both low and high amylose starches are particularly interesting because they are associated with industrial and processing properties as well as with human health and nutrition. So far, major attention has addressed the manipulation of starch composition in bread wheat, whereas durum wheat has been investigated to a much lesser extent. Approaches currently available to alter amylose/amylopectin ratio and tailor starch composition in durum wheat are presented.  相似文献   

20.
L-Ascorbic acid (AsA) and its related compounds play an important role as improvers in bread production. Addition of AsA and its related compounds, such as dehydro-L-AsA (DHA) and 2,3-diketo-L-gulonic acid (DKG), affected the rheological properties of flour-water dough during mixing, especially hardness. Addition of 10 or 100 ppm AsA increased the dough hardness of samples as compared with the control dough. Addition of DHA or DKG to dough only slightly increased hardness. Addition of p-quinone significantly increased the hardness. Both glutathione (GSH) and its oxidized form (GSSG) drastically decreased the hardness. Contents of AsA in the treated dough decreased and contents of DHA increased during mixing, suggesting that oxidation occurred. The oxidation rate of AsA was influenced by the concentration of AsA added. The improving effect of AsA on the rheological properties of flour-water dough seemed to be mostly dependent on reactive intermediate oxidation products such as O2-, while the contribution of DHA was rather limited.  相似文献   

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