小麦面团粘度影响因素研究进展

该文介绍国内外对小麦面团粘度影响因素研究进展;粘度是由面团粘结特性和内聚特性所共同决定一种特性,粘度过大会造成生产中断,且最终产品质量也会有所降低;麦谷蛋白及醇溶蛋白比例及结构、戊聚糖、1BL／1RS易位均对面团粘度产生影响。     

Secalin蛋白检测及其与面团黏性关系的研究

用SDS—PAGE检测了70个小麦品种是否带有黑麦Secalin蛋白，并测试了它们的面团黏性，用PCR检测了部分品种是否含有1RS染色体片断，结果表明：70％的品种为1B／1R易位系；有54．3％的品种面团发黏；带有黑麦Secalin蛋白的品种约有72．5％面团发黏，而不带有黑麦Secalin蛋白的品种只有30％面团发黏；影响面团黏性的主要因素为来源于黑麦的Secalin蛋白；PCR扩增结果表明，在我国存在不带有Sec-1基因的1B／1R小片断易位系。     

BAKING PERFORMANCE OF 1BL/1RS SOFT RED WINTER WHEATS

Baking performance of nine 1BL/1RS soft red winter wheat (SRWW) lines and six non‐1BL/1RS lines was assessed during two crop years, 1995–96 and 1996–97, and at two locations, Blacksburg and Warsaw, Virginia. The 1BL/1RS flours produced cookies with significantly smaller diameters than non‐1BL/1RS flours (p ≤ 0.0026) across both growing years and locations. There was a highly significant negative correlation (r =?0.709) between cookie spread and alkaline water retention capacity (AWRC) of SRWW flours. Overall, there was no significant difference (p = 0.2552) in biscuit volume of 1BL/1RS and non‐1BL/1RS flours. There were no significant differences in cake volumes of 1BL/1RS and non‐1BL/1RS flours when data from both years and locations were combined, p = 0.0710; or when Blacksburg and Warsaw locations were considered separately, p = 0.2009 and 0.1882, respectively. Finally, there were no significant differences in the texture of cakes made from 1BL/1RS and non‐1BL/1RS flours regardless of growing year or location. These results suggest that the 1BL/1RS translocation significantly reduces the cookie spread of SRWW flours but has no significant impact on biscuit or cake quality.     

Cell wall composition of 1B/1R translocation wheat grains

The cell wall composition and total dietary fibre content of 12 different winter wheat cultivars both without and with 1B/1R gene were analysed. Translocation wheat (with 1B/1R gene) had higher contents of extractable xylose and unextractable mannose residues than standard wheat (without 1B/1R gene). Three sieved flours of standard wheat, translocation wheat and rye respectively were used for further detailed studies. Water‐extractable arabinoxylan was isolated and fractionated on a DEAE‐cellulose column. The water‐eluted fraction of translocation wheat had a higher proportion of monosubstituted xylose residues than the same fraction of standard wheat, which is a typical feature of rye arabinoxylan. Molecular weight determination showed that rye water‐eluted arabinoxylans were larger than those of wheat. The molecular weight of translocation wheat arabinoxylan was lower than that of standard wheat and had a high polydispersity. Xylanase‐resistant arabinoxylan was extracted from all three flours, and NMR studies showed that wheat xylanase‐resistant arabinoxylan had a lower amount of monosubstituted xylose residues, while the rye fraction was rich in consecutive disubstituted xylose residues. Translocation wheat xylanase‐resistant arabinoxylan resembled that of standard wheat. © 2002 Society of Chemical Industry     

EXAMINATION OF RELATIONSHIPS BETWEEN THE RHEOLOGICAL PROPERTIES AND BAKING PERFORMANCE OF SELECTED SOFT WHEAT FLOURS

Results of farinograph and dough stickiness testing of seven 1BL/1RS positive and five 1BL/1RS negative soft, red, winter wheats (SRWW) were correlated with baking performance data. Biscuit volume was not significantly correlated with any farinograph parameters or with dough stickiness. Significant negative correlations were found between the diameters of cookies baked from SRWW flours and their farinograph percent water absorption, r =−0.825 (P < 0.01) and arrival times, r =−0.476 (P ≤ 0.05). Cake volume was negatively correlated with percent water absorption values of SRWW flours, r =−0.494 (P ≥ 0.05). Dough stickiness was positively correlated with cake tenderness, r = 0.486 (P ≥ 0.05). Significant positive correlations were also found between the cake tenderness of SRWW when grown in one of two locations, Blacksburg, Virginia, and farinograph departure times, r = 0.751 (P ≥ 0.05), and mixing stabilities, r = 0.749 (P ≥ 0.05). The results suggest that although bakers may encounter problems in using 1BL/1RS translocated SRWW flours in cookies because of reduced cookie spread, these flours can be successfully incorporated into biscuits and cakes.     

Wheat Flour Compound that Produces Sticky Dough: Isolation and Identification

Some wheats have a 1B/1R translocation and may produce flours that give sticky doughs, even with optimum mixing time and water absorption. Studies showed that the water-soluble fraction caused sticky dough. Dialysis experiments indicated that the responsible substance had low molecular weight. Ionic exchange showed it to be either neutral or negatively charged. Gel filtration chromatography indicated it was both carbohydrate and UV-absorbing. Saponification caused it to lose ability to cause sticky dough. The UV-absorbing material and the carbohydrate had to be linked for the compound to be active. HPLC mass spectrometry indicated the UV-absorbing fraction was ferulic acid and the carbohydrate was a hexose.     

Biscuit making properties of flours from hard and soft milling single variety wheats

Bench scale baking tests for two types of biscuits,¹ a hard sweet (HS) and a short sweet (SS), have been used to examine the biscuit making properties of a large number of flour samples from wheats grown in four consecutive years (1980–1983). Multiple regression models for prediction of biscuit properties using a range of standard cereal laboratory tests as independent variables on results from 1980–1981 harvest wheats confirmed earlier observations that such tests are of limited commercial value for biscuit flour specification. However the results of baking tests, with both types of biscuit, from single wheat varieties grown during 1981–1983 showed that flours from soft milling wheats (SMW) required less water to give biscuit doughs of standard consistency (measured instrumentally) than did flours from hard milling wheats (HMW). In addition biscuit doughs made with SMW flours gave greater oven spring, i.e. biscuits of lower bulk density, than doughs made from HMW flours. In each season the difference in the mean values of both parameters for flours milled from SMW and HMW was highly significant (P<0.001). With one exception the variability of the measured parameters within seasons was not significantly different between SMW and HMW. However within both SMW and HMW varieties highly significant differences (P<0.001) were observed between seasons for the mean values of both measured biscuit parameters. The effect of flour particle size on the biscuits was studied by regrinding a number of flours. With flours from both SMW and HMW reduction in particle size resulted in HS biscuits of higher density but SS biscuits of lower density.     

Wheat Flour Protein Concentrate Characterization by Biochemical, Physicochemical and Baking Tests

Protein concentrates before and after defatting from hard and soft wheat flours by water and 1% NaCl solution were characterized by lipid, sodium dodecyl sulphate (SDS) sedimentation, solubility, and breadmaking. Sedimentation values were higher for hard wheat flours than for soft, and in both about three times higher than in separated glutens. Solubility of proteins in SDS was reduced from ～23 to 31% in flours to ～3 to 19% in gluten concentrates. Defatting did not affect electrophoretic patterns but indicated lowered protein extractability. Gliadins and HMW glutenins were lower in extracts of separated glutens than in the extracts of doughs. Protein concentrates from fractionation with 1% salt solution, differed widely from those separated with water. This especially affected water absorption, dough development, and baking performance.     

Phytic acid content in milled cereal products and breads

Phytic acid was determined in cereal (brans, flours and milled wheat-products) and breads. The method was based on complexometric titration of residual iron (III) after phytic acid precipitation. The cereal flours showed values ranged between 3–4 mg/g for soft wheats, 9 mg/g for hard wheat and 22 mg/g for whole wheat. Corn, millet and sorghum flours reported a mean of 10 mg/g and oat, rice, rye and barley between 4 and 7 mg/g. Wheat brans had wide ranges (25–58 mg/g). The phytic acid for oat brans was half that of wheat bran (20 mg/g) and higher value (58 mg/g) than that for rice bran. The milling products (semolinas) from hard wheat exhibited 10 mg/g and soft wheat a mean of 23 mg/g. The breads made with single or mixture cereal flours exhibited ranges between 1.5 and 7.5 mg/g. The loss of phytic acid relative to unprocessed flours was between 20% for oat bread and 50% for white bread.     

A comparison of equilibrated lipid water systems and the effect of added lecithin on dough rheology of flour milling-streams

The lipid part of four wheat flour milling streams was extracted by ethanol. The flours were two spring wheats and two winter wheats, where one of each spring and winter wheats were obtained from the reduction-roll system and the other one from the break-roll system. Equilibrated lipid water mixtures were prepared and centrifuged to distinguish between non-polar and polar lipids. The lipids interacting with water were investigated in the microscope under polarised light to establish the presence of the lamellar liquid-crystalline phase. The stress relaxation behaviour of flour water doughs and doughs made with lamellar lecithin added were also studied. The largest amount of lipids able to form the lamellar liquid-crystalline phase was recovered for the winter wheat from the reduction milling-stream. The corresponding spring wheat also formed the lamellar phase, while the break flours did not. A large amount of oil phase was obtained from the two break flours. The rheological parameters increased to the same value for the two break flours and the two reduction flours when lecithin was added. This suggests that a flour containing protein and lipids of approximately the same quality will be improved to the same extent when lamellar lecithin is added. © SCI 1998.     

QUALITY ATTRIBUTES OF CANADIAN HARD WHITE SPRING WHEAT

Quality characteristics of five pilot‐scale milled Canadian hard white spring wheats were compared to a No.1 grade commercial composite Canada Western Red Spring (1CWRS) wheat. One metric ton of samples was milled on the Canadian International Grains Institute pilot Buhler mill (Buhler AG, Uzwil, Switzerland) into straight‐grade (SG), 85% and whole wheat flours. At the SG extraction level, the white wheats with their lighter colored seed coats had improved milling yields (up to 2.6%) and lower ash (0.01–0.09%) than the 1CWRS control wheat. Majority of white wheat flours had higher protein contents than the 1CWRS control flours for all flour extractions. Based on dough rheological properties of the flours, three of the white wheats (Kanata, Snowbird and BW 275 ) were equal to or better than the red 1CWRS control for nearly all farinograph and mixograph parameters at all flour extractions other than farinograph absorption. Two of the white wheat lines (RL 4863 and RL 4858 ) had excessively weak and overly strong dough properties, respectively. Evaluation of pan bread, bagels and tortillas showed that white wheats generally produced end‐products that were comparable or superior to 1CWRS and that their most significantly positive quality compared to 1CWRS was their substantially lighter colored end‐products.     

Promoting dough viscoelastic structure in composite cereal matrices by high hydrostatic pressure

The impact of high hydrostatic pressure (HP) treatment on dough viscoelastic reinforcement of highly-replaced wheat cereal matrices has been investigated. The gelatinisation/pasting and gelling profiles of HP hydrated oat, millet, sorghum and wheat flours, and the small and large deformation rheological parameters of blended wheat/non-wheat doughs were determined. Oat, millet, sorghum and wheat hydrated flours, at dough yield (DY) 160 and 200, were treated for 10 min at 0.1, 200, 350 or 500 MPa. Regardless the nature of the cereal, HP changes flour viscometric features, particularly in softer doughs (DY 200), leading to increased values for viscosity parameters, concerning pasting and paste cooking. Incorporation of 350 MPa pressure-treated flours into bread dough formulation provided increased dynamic moduli values, particularly for wheat and oat/wheat blends, associated to a reinforced dough structure. Highly-replaced composite dough samples treated at 500 MPa proved to be extremely stiff, resistant to stretch, low cohesive and low extensible, and thus not suitable for breadmaking.     

THE RHEOLOGICAL BASIS OF DOUGH STICKINESS

Stickiness in wheat flour doughs was studied as a function of rheological and surface properties. Adhesion was measured using a modified peel test at various water additions, peel rates and peel layer thicknesses. Peeling energy gave a strong positive correlation with subjective bakery stickiness ratings. Peeling forces were highly rate dependent and showed transitions from sticky to nonsticky behvaiour with increasing rate of peeling. Dynamic storage modulus showed a negative correlation with stickiness ratings, suggesting stickiness is primarily a rheologically controlled process. Stress relaxation gradients were greater for sticky doughs and were very similar to peeling force vs. rate slopes, again indicating that adhesion is principally a function of the rheological properties of the dough. Surface tension measurements of sticky and nonsticky dough/liquor interfaces showed no significant differences and are typical of protein solutions. Calculated values of the interfacial surface energy between dough and interface were about 100 mJ/m², typical of secondary bonding interactions such as polar or van der Waals bonding.     

Carbohydrate Digestibility and Resistant Starch of Steamed Bread

Sixteen Australian hard and soft wheats and two U.S. hard wheats were milled into flours (break and reduction) for preparation of steamed breads. Chemical composition and rheological properties of the flour were determined. Steamed breads were analyzed for carbohydrate digestibility and resistant starch. There was no relationship between flour type, protein content and specific volume of steamed breads. Carbohydrate digestibility of steamed breads from soft wheat flour was higher than that of breads from hard wheat flour. Reduction flours produced steamed breads with higher carbohydrate digestibility than break flours. Resistant starch was higher in steamed breads from soft wheat flours than in those from hard wheat flours. Reduction flour produced higher resistant starch levels than break flours. Commercial white bread had resistant starch levels similar to those of steamed breads from soft wheat flour and hard wheat reduction flour.     

Effects of enzymes in fibre-enriched baking

The aim of the present study was to improve the quality of fibre-enriched wheat breads by enzymic treatment of the fibre fraction. The suitability of different enzymes in fibre-enriched baking and their effects on the dietary fibre content and the ratio of insoluble: soluble fibre content of the breads were studied. The enzyme preparations used were a hemicellulolytic culture filtrate of Trichoderma reesei, a specific (pI 9) xylanase of T reesei and Fermizyme, an α-amylase preparation containing a standardised level of hemicellulase activity. Rye bran was extracted in water (10% (w/w) suspension) to determine the solubilities of the β-glucans and pentosans. Addition of T reesei culture filtrate significantly increased the amount of extractable pentosan obtained from nonautoclaved rye bran. Rye bran supplementation (5%) of wheat flour increased the farinograph absorption and dough development time, but had little or no effect on stability and softening of the dough. The added enzymes decreased dough stability and increased softening. Addition of enzymes caused significant differences in the stickiness of the wheat doughs both with (P<0·003) and without (P<0·001) rye bran. Fermizyme significantly increased the stickiness of wheat doughs both with and without rye bran. The baking results of the fibre-enriched breads were improved by the added enzymes. Addition of T reesei culture filtrate increased the specific volume of the wheat breads both with and without rye bran by almost 20%. Enzyme mixtures were more efficient than individual xylanase in softening the bread crumb and reducing the staling rate of wheat breads both with and without rye bran. Incorporation of enzymes reduced the total dietary fibre content of the breads, but at least doubled the amount of soluble pentosan. The proportions of fluorescent cell walls in the breads were detected by microscopical image analysis. Enzyme addition caused the surface area of insoluble cell walls originating from wheat flours to decrease, suggesting that the enzymes exert more effects on wheat endorsperm cell walls than on bran particles. © 1998 SCI.     

UNIAXIAL COMPRESSIBILITY OF BLACKGRAM DOUGHS BLENDED WITH CEREAL FLOURS

The uniaxial compression characteristics of papad dough (moisture content 62%, dry basis), made from blackgram flour as well as after incorporation of different types of cereal (rice, sorghum and wheat) flours at different levels (20 and 40%), were determined. The stress-strain data can be interrelated by a power law type equation. The sensory attributes (stickiness, firmness, elasticity and ease of flattening/rolling) were correlated with the energy for compression, deformability modulus and apparent biaxial elongational viscosity. Inelastic doughs resulted from the blackgram dough; doughs with 20% rice or wheat blends were also inelastic but sorghum samples were elastic. The deformability modulus for sorghum doughs were extremely high. The blackgram dough as well as the wheat blended doughs were the easiest doughs to roll/flatten. Blended dough consisting of wheat flour (at 20 and 40% level) or rice flour up to 20% level was suitable for making cereal-blended papad doughs.     

The influence of 1B/1R chromosome translocation on gluten protein composition and technological properties of bread wheat

The Austrian bread wheat Amadeus without and with 1BL/1RS translocation and three further translocation genotypes with known HMW subunit compositions were grown under the same environmental conditions. Their flours were characterised by the determination of crude protein content and, partly, by the determination of glutathione and cysteine. Furthermore, the qualitative and quantitative composition of gluten protein types was analysed by a combined extraction and reversed phase HPLC procedure. Dough development time, maximum resistance and extensibility of dough and gluten, and bread volume were determined by means of microscale methods. Protein, glutathione and cysteine contents of flours were only slightly influenced by translocation. The HPLC patterns of gliadins and glutenin subunits showed that translocation caused characteristic changes concerning ω‐gliadins, γ‐gliadins and LMW subunits of glutenin. The amount of ω 1,2‐gliadins was significantly increased and that of LMW subunits decreased. The effect of translocation on the rheological properties of dough and gluten was characterised by a strongly reduced dough development time, reduced maximum resistance and increased extensibility. Bread volume was decreased by about 10%. The amount of glutenin subunits was correlated with dough development time, resistance of dough and gluten, and bread volume to a higher extent (r = 0.79–0.91) than the amount of gliadins (r = 0.52–0.80). Correlation coefficients for LMW subunits were higher (r = 0.82–0.88) than those for HMW subunits (r = 0.35–0.61) when all five wheats were included. Instead, when only translocation lines were considered, HMW subunits (r = 0.89–0.98) were more important than LMW subunits (r = 0.64–0.86). Altogether, the results demonstrate that translocation causes important quantitative as well as qualitative changes in gluten protein composition which can be efficiently determined by reversed phase HPLC. © 2000 Society of Chemical Industry     

Physical properties of enzyme-supplemented doughs and relationship with bread quality parameters

The textural properties of wheat doughs made with different commercial amylases, xylanases/pentosanases, lipases and glucose-oxidase, singly and in mixed combinations, were investigated. Parameters from the texture profile analysis (TPA) and measurement of stickiness (Chen and Hoseney test) were determined after mixing the dough and after it had rested for 3.5 h. Resting of doughs led to softer and less cohesive doughs, with higher adhesive properties. Enzymes acted quickly and induced significant changes in the textural properties of doughs immediately after mixing. The influence of enzymes continued during resting. Xylanases/pentosanases substantially reduced dough consistency and increased stickiness, while addition of glucose-oxidase and specific lipases overcame these effects. Strong correlations could be established between different TPA parameters and stickiness and bread quality characteristics (i.e. volume, density and texture). Bread quality could be described by a single or multiple linear combination of textural variables.     

Physical properties of enzyme-supplemented doughs and relationship with bread quality parameters

 The textural properties of wheat doughs made with different commercial amylases, xylanases/pentosanases, lipases and glucose-oxidase, singly and in mixed combinations, were investigated. Parameters from the texture profile analysis (TPA) and measurement of stickiness (Chen and Hoseney test) were determined after mixing the dough and after it had rested for 3.5 h. Resting of doughs led to softer and less cohesive doughs, with higher adhesive properties. Enzymes acted quickly and induced significant changes in the textural properties of doughs immediately after mixing. The influence of enzymes continued during resting. Xylanases/pentosanases substantially reduced dough consistency and increased stickiness, while addition of glucose-oxidase and specific lipases overcame these effects. Strong correlations could be established between different TPA parameters and stickiness and bread quality characteristics (i.e. volume, density and texture). Bread quality could be described by a single or multiple linear combination of textural variables. Received: 21 May 1997 / Revised version: 10 July 1997     

Significance of lipid binding on the functional and nutritional profiles of single and multigrain matrices

Lipid fractions and starch- and protein-lipid binding of single and blended oat, rye, buckwheat and wheat flour, dough and bread matrices were investigated, and results correlated with the functional and nutritional properties of the grain matrices during mixing and baking. Non-starch lipid was the most prominent fraction in terms of absolute content and as a percentage of total lipids. Free lipids, starch lipids and bound lipids were, respectively, the major, intermediate and minor lipid fractions in flours, doughs and breads. Great differences in total lipid content due to sampling result in divergences amongst lipid fraction content and distribution, especially for starch and bound lipid fractions. Lipids bound to proteins during dough mixing are translocated and bound to starch during baking. In blended samples, the higher fibre content seems to provoke a reduction of the lipid–protein and lipid–starch linkages due to interactions between fibres and endogenous biopolymers. Starch lipid showed the most significant correlations with parameters related to dough and bread performance during breadmaking, especially over the mixing step. Valuable fresh bread functional characteristics, such as high specific volume and high sensory score for softness and overall acceptability, correspond to a starch lipid’s increase due to mixing. The higher the free and starch lipids decrease by reason of temperature treatment—baking—the larger the starch hydrolysis and the higher β-glucans and total dietary fibre contents.