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1.
The beneficial effects of a new recombinant lipase (Rhizopus chinensis lipase [RCL]) and transglutaminase (TG) were investigated on frozen dough systems and their breadmaking quality. Rheological properties and microstructure of doughs were measured using a dynamic rheometer, rheofermentometer F3, and scanning electron microscopy (SEM). Measurements of viscoelastic properties showed that both G′ and G″ of dough containing RCL and TG were greater than those of the control after 35 days of frozen storage. The SEM micrographs showed that dough containing RCL and TG had the most starch granules embedded in or attached to the gluten network, and the gluten seemed more powerful and resilient than for the control dough after 35 days of frozen storage. Results of the gas production and dough development tests indicated that RCL and TG improved the rheofermentative characteristics of frozen dough. RCL and TG could improve water‐holding capacity and significantly increase the glycerol content of the control dough. Image analyses showed that bread crumbs containing RCL and TG had a more open network and uniform crumb structure, which resulted in higher specific volume. This combination also yielded a product with higher sensory scores for test breads.  相似文献   

2.
The effect of transglutaminase (TG) on glutenin macropolymer (GMP) properties could help to understand changes in bread quality. The aim of the present study was to analyze modifications in GMP and dough properties caused by TG addition. Transglutaminase introduced cross‐links to gluten proteins, mainly high molecular weight glutenins. This effect modified the protein structure and markedly increased dough strength. These changes in the structure of glutenins increased SDS solubility and decreased GMP content and GMP storage modulus. However, TG increased GMP particle size, notably at higher doses. TG affected rheological characteristics of dough in that increasing TG doses decreased tan δ, and increased G'. In all the studies conducted, the TG increased GMP polymer size, but contrary to what was expected, this increase did not involve an increase in GMP content. These results confirmed the effect of TG on dough quality and the great differences found with different TG doses.  相似文献   

3.
《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   

4.
The rheological properties of dough and gluten are important for end‐use quality of flour but there is a lack of knowledge of the relationships between fundamental and empirical tests and how they relate to flour composition and gluten quality. Dough and gluten from six breadmaking wheat qualities were subjected to a range of rheological tests. Fundamental (small‐deformation) rheological characterizations (dynamic oscillatory shear and creep recovery) were performed on gluten to avoid the nonlinear influence of the starch component, whereas large deformation tests were conducted on both dough and gluten. A number of variables from the various curves were considered and subjected to a principal component analysis (PCA) to get an overview of relationships between the various variables. The first component represented variability in protein quality, associated with elasticity and tenacity in large deformation (large positive loadings for resistance to extension and initial slope of dough and gluten extension curves recorded by the SMS/Kieffer dough and gluten extensibility rig, and the tenacity and strain hardening index of dough measured by the Dobraszczyk/Roberts dough inflation system), the elastic character of the hydrated gluten proteins (large positive loading for elastic modulus [G′], large negative loadings for tan δ and steady state compliance [Je0]), the presence of high molecular weight glutenin subunits (HMW‐GS) 5+10 vs. 2+12, and a size distribution of glutenin polymers shifted toward the high‐end range. The second principal component was associated with flour protein content. Certain rheological data were influenced by protein content in addition to protein quality (area under dough extension curves and dough inflation curves [W]). The approach made it possible to bridge the gap between fundamental rheological properties, empirical measurements of physical properties, protein composition, and size distribution. The interpretation of this study gave indications of the molecular basis for differences in breadmaking performance.  相似文献   

5.
An attempt was made to understand the physicochemical attributes that are the basis of physical differences between alkaline and salted noodle doughs. Flour and dough properties of one soft and three hard‐grained wheat cultivars were observed. Doughs were made with either sodium chloride or sodium carbonate. Each formulation variant was tested at both high and low water additions. Samples for glutenin macropolymer (GMP) isolation were taken at selected noodle dough processing stages. When a 1.67% w/v Na2CO3 solution was used for mixograph testing, dough characteristics were radically altered and differences between cultivars were masked. In lubricated squeezing flow (LSF) testing, hard wheat noodle doughs had significantly (P < 0.01) longer relaxation times and higher % residual force values than soft wheat doughs in both the salted and alkaline variants. LSF maximum force and biaxial viscosity were significantly higher in alkaline doughs than salted. GMP extracted from alkaline doughs was gummy and sticky, and was more opaque than GMP from salted doughs. GMP weight decreased sequentially when extracted from samples taken in the active phase (mix, compound, sheet) of noodle dough processing and decreased more in alkaline doughs. GMP weight increased more after 24 hr of dough rest in salted doughs. GMP gel strength was noticeably higher in GMP extracted from alkaline doughs. After dough resting, alkaline GMP gel strength significantly increased, whereas it decreased in GMP from salted doughs, suggesting a role for GMP in the increased stiffness of alkaline noodle doughs.  相似文献   

6.
Rheological characteristics of dough and glutenin macropolymer (GMP) extracted thereof were investigated. Three single enzymes, pentosanase (PP), glucoseoxidase (GLZ), and laccase (LAC), and their combinations were used. GLZ gave the least extensible and most resistant dough, and pentosanase/glucoseoxidase (PPGLZ) resulted in dough with improved extensibility. The enzymes improved gluten quality. The glutenin macropolymer (GMP) was characterized in terms of wet weight, protein content, pentosan association, and dynamic rheological properties. Enzymatic addition decreased the wet weight of GMP but increased the protein content. PP decreased the content of pentosans on the GMP, but single oxidases increased the content of pentosans associated with GMP. PP did not modify the elastic modulus (G') of the GMP, whereas GLZ increased G' by increasing the polymerization of proteins and LAC diminished G'. The combination PPGLZ produced a synergic increase of G'.  相似文献   

7.
The high molecular weight glutenin subunits (HMW‐GS) play an important role in governing the functional properties of wheat dough. To understand the role of HMW‐GS in defining the basic and applied rheological parameters and end‐use quality of wheat dough, it is essential to conduct a systematic study where the effect of different HMW‐GS are determined. This study focuses on the effect of HMW‐GS on basic rheological properties. Eight wheat lines derived from cvs. Olympic and Gabo were used in this study. One line contained HMW‐GS coded by all three loci, three lines were each null at one of the loci, three lines were null at two of the loci and one line null at all three loci. The flour protein level of all samples was adjusted to a constant 9% by adding starch. In another set of experiments, in addition to the flour protein content being held at 9%, the glutenin‐to‐gliadin ratio was maintained at 0.62 by adding gliadin. Rheological properties such as elongational, dynamic, and shear viscometric properties were determined. The presence of Glu‐D1 subunits (5+10) made a significantly larger contribution to dough properties than those encoded by Glu‐B1 (17+18), while subunit 1, encoded by Glu‐A1, made the least contribution to functionality. Results also confirmed that HMW‐GS contributed to strength and stability of dough.  相似文献   

8.
The effect of flour type and dough rheology on cookie development during baking was investigated using seven different soft winter wheat cultivars. Electrophoresis was used to determine the hydrolyzing effects of a commercial protease enzyme on gluten protein and to evaluate the relationships between protein composition and baking characteristics. The SDS‐PAGE technique differentiated flour cultivars based on the glutenin subunits pattern. Electrophoresis result showed that the protease degraded the glutenin subunits of flour gluten. Extensional viscosities of cookie dough at all three crosshead speeds were able to discriminate flour cultivar and correlated strongly and negatively to baking performance (P < 0.0001). The cookie doughs exhibited extensional strain hardening behavior and those values significantly correlated to baking characteristics. Of all rheological measurements calculated, dough consistency index exhibited the strongest correlation coefficient with baking parameters. The degradation effects of the protease enzyme resulted in more pronounced improvements on baking characteristics compared with dough rheological properties. Stepwise multiple regression showed that the dough consistency index, the presence or absence of the fourth (44 kDa) subunit in LMW‐GS and the fifth subunit (71 kDa) subunit in HMW‐GS were predominant parameters in predicting cookie baking properties.  相似文献   

9.
Effect of freezing and frozen storage of doughs on bread quality   总被引:3,自引:0,他引:3  
The effects of freezing and storage in frozen conditions on bread quality, crumb properties, and aggregative behavior of glutenins were analyzed. The effect of different additives on bread quality was also studied. The results obtained showed that freezing and storage at -18 degrees C decreased the bread quality. Samples stored in frozen conditions supplemented with diacetyl-tartaric acid ester of monoglycerides, gluten, and guar gum produced breads of greater volume and more open crumb structure than those prepared with the base formulation (without additives). All additives analyzed increased the proof time. Crumb firmness increased with dough frozen storage and bread aging time at 4 degrees C. A decrease in the amount of glutenin subunits of high molecular mass was observed by electrophoresis analysis of the SDS-soluble proteins aggregates extracted from the frozen dough. This result suggested that the protein matrix of bread underwent depolymerization during storage in frozen conditions.  相似文献   

10.
The effects of freezing and frozen storage of bread dough and compressed yeast on bread quality were studied. Besides, the effects of compressed yeast freezing on cell viability, gas production and release of substances by the yeast cells were examined. Freezing and frozen storage of dough made with fresh yeast had more negative effects on baking quality than the addition of frozen yeast to dough. When the compressed yeast is frozen and stored at ‐18°C, the CO2 production decreased, while the amount of dead cells, the total protein, and the total reducing substances leached from the yeast increased as the length of yeast frozen storage increased. SDS‐PAGE showed that the substances leached from frozen yeast caused an increase in the solubility of some gluten proteins. On the other hand, size‐exclusion chromatography (SEC) pointed out that the relative amount of two protein fractions of low molecular weight leached from frozen yeast increased for longer yeast frozen storage periods. The yeast leachates had an adverse effect on loaf volume.  相似文献   

11.
Understanding the relationship between basic and applied rheological parameters and the contribution of wheat flour protein content and composition in defining these parameters requires information on the roles of individual flour protein components. The high molecular weight glutenin subunit (HMW‐GS) proteins are major contributors to dough strength and stability. This study focused on eight homozygous wheat lines derived from the bread wheat cvs. Olympic and Gabo with systematic deletions at each of three HMW‐GS encoding gene loci, Glu‐A1, Glu‐B1, and Glu‐D1. Flour protein levels were adjusted to a constant 9% by adding starch. Functionality of the flours was characterized by small‐scale methods (2‐g mixograph, microextension tester). End‐use quality was evaluated by 2‐g microbaking and 10‐g noodle‐making procedures. In this sample set, the Glu‐D1 HMW‐GS (5+10) made a significantly larger contribution to dough properties than HMW‐GS coded by Glu‐B1 (17+18), while subunit 1 coded by Glu‐A1 made the smallest contribution to functionality. These differences remained after removing variations in glutenin‐to‐gliadin ratio. Correlations showed that both basic rheological characteristics and protein size distributions of these flours were good predictors of several applied rheological and end‐use quality tests.  相似文献   

12.
Transglutaminase (TG) catalyzes the formation of nondisulfide covalent crosslinks between peptide‐bound glutaminyl residues and ∊‐amino groups of lysine residues in proteins. Crosslinks among wheat gluten proteins by TG are of particular interest because of their high glutamine content. Depolymerization of wheat gluten proteins by proteolytic enzymes associated with bug damage causes rapid deterioration of dough properties and bread quality. The aim of the present study was to investigate the possibility of using TG to regain gluten strength adversely affected by wheat bug proteases. A heavily bug‐damaged (Eurygaster spp.) wheat flour was blended with sound cv. Augusta or cv. Sharpshooter flours. Dynamic rheological measurements, involving a frequency sweep at a fixed shear stress, were performed after 0, 30, and 60 min of incubation on doughs made from sound or blended flour samples. The complex moduli (G* values) of Augusta and Sharpshooter doughs blended with 10% bug‐damaged flour decreased significantly after 30 min of incubation. These dough samples were extremely soft and sticky and impossible to handle for testing purposes after 60 min of incubation. To test the possibility of using TG to counteract the hydrolyzing effect of bug proteases on gluten proteins, TG was added to the flour blends. The G* values of TG‐treated sound Augusta or Sharpshooter doughs increased significantly after 60 min of incubation. The G* values of the Augusta or Sharpshooter doughs blended with bug‐damaged flour increased significantly rather than decreased after 30 and 60 min of incubation when TG was included in the dough formulation. This indicates that the TG enzyme substantially rebuilds structure of dough hydrolyzed by wheat bug protease enzymes.  相似文献   

13.
This study investigated the antifreeze activity (AF) of γ‐polyglutamic acid (γ‐PGA), freezing resistance of yeast cells and sweet dough, and the mechanism influenced by γ‐PGA. Properties studied included AF of γ‐PGA, water‐holding capacity of flour, survival ratio and oxidation resistance capability of yeast cells, ice melting enthalpy (ΔH), and fermentation and breadmaking properties of sweet dough. The AF of γ‐PGA was 8.03 g of unfrozen water/g of sample, indicating good AF. γ‐PGA was tested on yeast cells and sweet dough stored frozen for 0, 1, 2, 4, and 8 weeks at four levels (0, 0.5, 1, and 3%). Survival ratio of yeast cells with γ‐PGA was significantly higher than the corresponding control. A possible mechanism might be related to the modulation of oxidation resistance capability of yeast cells by γ‐PGA. A decrease in glutathione release from frozen yeast cells and an increase in water‐holding capacity of wheat dough were observed with the addition of γ‐PGA. In the presence of γ‐PGA, ΔH, ice melting temperature, and proofing time of frozen sweet dough decreased significantly, and fermentation parameters improved, compared with the corresponding control sample. Specific volume of bread made from frozen sweet dough with 0.5, 1, and 3% γ‐PGA increased by 6.3, 8.9, and 3.3%, respectively, after 8 weeks of frozen storage. γ‐PGA enhanced the freezing resistance of yeast cells and sweet dough effectively, and the effect on specific volume of bread was not linear, with 1% showing better results.  相似文献   

14.
Dairy ingredients are added to bakery products to increase nutritional and functional properties. Sodium caseinate (SC) and whey protein concentrate (WPC) were incorporated into frozen dough. WPC was subjected to heat treatment (WPCHT) to eliminate undesirable weakening of the gluten network. 2% SC or 4% SC decreased proof time, increased loaf volume, and improved texture. Effects of adding 4% SC on baking quality were similar to adding ascorbic acid (AA) and diacetyl tartaric acid esters of monoglycerides (DATEM). WPC increased proof time, decreased volume, and negatively affected texture. Heat treatment of WPC improved baking performance. Bread with WPCHT had volume similar to that of the control without dairy ingredients. Adding 4% SC decreased resistance to extension (R5cm measured with the extensigraph), while adding 4% WPC increased extensibility. Dynamic oscillation testing determined the effects of the ingredients on fundamental rheological properties. WPC decreased storage modulus (G′) and loss modulus (G″), while heat treatment of WPC increased G′ and G″. Confocal laser scanning microscopy (CLSM) showed that milk proteins affect frozen dough ultrastructure. Frozen doughs with SC had an enhanced gluten network compared with the control, while untreated WPC appeared to interfere with the gluten network.  相似文献   

15.
Disadvantages of frozen doughs are their variable performance and loss of stability over long‐term frozen storage. Changes in rheological properties of frozen doughs have been reported to be due to the physical damage of the gluten network caused by ice crystallization and recrystallization. The objective of this study was to determine the effect of hydrophilic gums on ice crystallization and recrystallization for improvement of the shelf‐life stability of frozen dough. The present research involved use of the Hard Red Spring wheat cultivar Grandin and hydrophilic gums such as carboxymethyl cellulose (CMC), gum arabic, kappa carrageenan (κ‐carrageenan), and locust bean gum at three different levels each on doughs stored frozen for up to 16 weeks. The dough characteristics were analyzed after day 0, day 1, and after 4, 8, 12, and 16 weeks of frozen storage using data from differential scanning calorimetry (DSC), water activity, extensigraph, and proof time. The ΔH value of freezable water endothermic transitions obtained using DSC increased with storage time for all treatments. However, addition of different levels of the four gums lowered the ΔH value, indicating a decrease in freezable water. Doughs with locust bean gum gave a higher peak force, measured using the Kieffer dough extensibility rig of the texture analyzer, and lower proof time, indicating better retention of baking quality. Maximum resistance to extension increased upon addition of 1 and 3%; CMC; 1 and 3%; κ‐carrageenan; and 1, 2, and 3% locust bean gum as compared with the control. The various periods of storage or gum treatments did not affect the water activity of the thawed frozen doughs. Doughs with locust bean gum gave significantly lower proof time compared with the other treatments and the control. CMC gave the second lowest values, followed by gum arabic treatment. Addition of κ‐carrageenan increased the proof time compared with the control. In summary, locust bean gum, gum arabic, and CMC improved the dough characteristics to varying degrees. κ‐Carrageenan was the only gum that showed a detrimental effect on frozen dough.  相似文献   

16.
Wheat cultivars possessing quality attributes needed to produce optimum quality tortillas have not been identified. This study investigated the effect of variations in high‐molecular‐weight glutenin subunits encoded at the Glu‐1 loci (Glu‐A1, Glu‐B1, and Glu‐D1) on dough properties and tortilla quality. Flour protein profiles, dough texture, and tortilla physical quality attributes were evaluated. Deletion at Glu‐D1 resulted in reduced insoluble polymeric protein content of flour, reduced dough compression force, and large dough extensibility. These properties produced very large tortillas (181 mm diameter) compared with a control made with commercial tortilla wheat flour (161 mm). Presence of a 7 + 9 allelic pair at Glu‐B1 increased dough strength (largest compression force, reduced extensibility, and small‐diameter tortillas). Deletion at Glu‐A1 produced large tortillas (173 mm) but with unacceptable flexibility during storage (score <3.0 at day 16). In general, presence of 2* at Glu‐A1, in combination with 5 + 10 at Glu‐D1, produced small‐diameter tortillas that required large force to rupture (tough texture). Presence of 2 + 12 alleles instead of 5 + 10 at Glu‐D1 produced tortillas with a good compromise between diameter (>165 mm) and flexibility during storage (>3.0 at day 16). These allele combinations, along with deletion at Glu‐D1, show promise for tortilla wheat development.  相似文献   

17.
Breadmaking properties (bread height, mm, and specific volume, cm3/g ) showed marked deterioration when bread dough was frozen and stored at ‐20°C for one day. However, these properties of bread dough baked after storage for three to six days were not further deteriorated as compared with that baked after one day of storage. A large amount of liquid was oozed from the frozen‐and‐thawed bread dough. The liquid was separated from the bread dough by centrifugation (38,900 × g for 120 min at 4°C), and collected by tilting the centrifuge tube at an angle of 45° for 30 min. There was a strong correlation between the amount of centrifuged liquid and breadmaking properties (bread height and specific volume). The mechanism responsible for the oozing of liquid in frozen‐and‐ thawed bread dough was studied. The presence of yeast and salt in bread dough was suggested to be closely related to the amount of centrifuged liquid, and fermented products particularly had a large effect on the amount of centrifuged liquid.  相似文献   

18.
The uniaxial elongational and shear rheology of doughs varying in either the protein content or glutenin‐to‐gliadin ratio were investigated. Increasing the protein content at constant glutenin‐to‐gliadin ratio increased the strain‐hardening properties of the dough, as shown by increasing elongational rupture viscosity and rupture stress. Glutenin and gliadin had a more complex effect on the elongational properties of the dough. Increased levels of glutenin increased the rupture viscosity but lowered the rupture strain, while elevated gliadin levels lowered the rupture viscosity but increased the rupture strain. These observations provide rheological support for the widely inferred role of gliadin and glutenin in shaping bread dough rheology, namely that gliadin contributes the flow properties, and glutenin contributes the elastic or strength properties. The shear and elongational properties of the doughs were quite different, reflecting the dissimilar natures of these two types of flow. Increasing protein content lowered the maximum shear viscosity, while increasing the glutenin‐to‐gliadin ratio increased maximum shear viscosity. Strong correlations between the results of basic and empirical rheology were found. These basic, or fundamental, rheological measurements confirmed prior empirical studies and supported baking industry experience, highlighting the potential of basic rheology for bread and wheat research.  相似文献   

19.
Frozen storage increased the amount of liquid phase and decreased the storage modulus of water-flour mixtures. The liquid phase was studied by ultracentrifugation. The most significant change occurred during the first week of storage. The negative effects of ice crystals could be controlled by reducing the water content, which was seen as smaller amounts of liquid phase and higher dough rigidity after frozen storage (G′ values). Reduced water content also prevented an increase in the self-diffusion coefficient during frozen storage (1H NMR studies). Prefermented frozen doughs were examined under different conditions: with and without Skimo (additive from Puratos, Belgium), prefermentation time of 25 or 40 min, and reduced water content. The results obtained with autoradiographic method correlated best with the baking results and showed that S-kimo and shorter prefermentation time improve the water distribution of frozen prefermented doughs. Doughs contained small ice crystals after frozen storage and there were no large water patches in thawed doughs. Reduced water content and exclusion of S-kimo decreased the liquid phase of fermented doughs and increased dough rigidity. The baking properties of frozen prefermented doughs were better predicted by large deformation rheology (expansion potential of samples during oscillation). In general, flour quality had an obvious effect on the parameters. There was no correlation between the rheological properties and the values of liquid phase, but in most cases a high correlation between the total water content and rheological properties was observed.  相似文献   

20.
Empirical and fundamental rheology measurements were made on fresh and frozen dough to investigate the effects of freezing, frozen storage, and additives. These results were compared with results of a standard baking test. Four formulations were tested: a control dough, and doughs with additions of 100 ppm of ascorbic acid (AA), 0.5% sodium stearoyl lactylate (SSL), and 0.5% diacetyl tartaric acid esters of monoglycerides (DATEM). Rheological and baking tests were performed on fresh doughs and on doughs after two, five, and eight weeks of frozen storage. Resistance to extension was higher for doughs with additives in fresh and frozen doughs. There was a decrease in resistance to extension due to freezing. Complex modulus in fresh doughs was highest for doughs with SSL. There was a decrease complex modulus after freezing and thawing. In frozen doughs at 10 Hz, doughs with additives had higher complex modulus values and lower phase angle values when compared to the control. The additives used all had a positive effect on proof time, loaf volume, and crumb firmness, and all formulations deteriorated in quality during frozen storage. Resistance to extension and complex modulus were positively correlated with loaf volume (r = 0.86 and r = 0.64, P < 0.01). Phase angle was negatively correlated with loaf volume (r = -0.74, P < 0.01).  相似文献   

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