EXTENSIONAL FLOW STUDIES ON WHEAT FLOUR DOUGHS WITH DIFFERENT PROTEIN CONTENT1

Uniaxial compression technique was used to relate the rheological behavior of dough to wheat quality for bread. Dough of nine flours of the cultivar Rayon, grown in three different regions of Sonora, Mexico, and with a protein content from 10% to 12.8%, were studied using the lubricated squeezing‐flow test connected to a texturometer. Wheat flour quality determinations were protein, moisture and ash content, dry gluten, falling number, and sedimentation volume. Traditional dough rheological evaluations were made with the farinograph and alveograph. The baking test was also done. The extensional viscosity was measured at three crosshead speeds (0.2, 0.5, and 1.0 mm/min). Extensional viscosity, measured at the lowest speed, significantly (P < 0.05) and negatively correlated with protein content (r = ‐0.63) and bread volume (r = ‐0.72). The rheological behavior of wheat doughs during lubricated uniaxial compression showed dependence on the strain rate as demonstrated by the patterns of the extensional viscosity curves.     

Comparison of uniaxial/biaxial extensional rheological properties of mixed dough with traditional rheological test results: relationship with the quality of steamed bread

The formula and preparation of steamed bread are different from those of western bread. The extensional rheological behaviour plays a key role in the development of steamed bread dough. However, there are inadequate studies on the rheological properties of mixed dough with yeast. In this study, the relationship between properties of dough in the presence or absence of yeast was elucidated. Besides, the flour characteristics and quality of steamed bread prepared from different wheat varieties were evaluated. The uniaxial/biaxial extensional rheological properties of wheat dough were compared with traditional rheological test results. Large deformations in the extensional properties were measured by Extensograph and the Kieffer extensibility rig, while the biaxial extension was quantified using uniaxial compression. These characteristics of dough and flour correlated with each other in different ways. Correlation analysis illustrated that the uniaxial extensional rheological properties of dough with yeast better indicated the quality of the steamed bread. Moreover, the total work for breakage of the dough with yeast was the best predictor for specific volume of steamed bread. The texture-based properties of steamed bread showed correlation with biaxial extension viscosity. The rheological tests provide useful information for evaluating wheat flour and steamed bread quality.     

Brama australis gel obtention and rheological characterization

Gelatine from marine sources has been looked upon as a possible alternative to bovine and porcine gelatine. Common problems connected with fish gelatine from cold water species, such as those from Chilean coast, are low gelling and melting temperature and low gel modulus. Squeezing flow technique was applied to obtain rheological parameters as function of moisture content, temperature dependence of extensional viscosity, etc. This work studied effects of pH and concentration on the extensional viscosity of brama australis fish gelatine gels using lubricated squeezing flow method and obtained that biaxial extensional viscosity increases with increasing Brama australis fish gelatine concentration.     

Functional Characteristics of the Mucilaginous Polysaccharides Derived from Cowpea (Vigna sinensis), Black Gram (Phaseolus mungo) and Linseed (Linum usitatissimum)

The cowpea polysaccharides had the maximum viscosity at around pH 6 and it decreased with increase in temperature but increased with increase in concentration. Both black gram and cowpea polysaccharides stabilized against thermal disruption the foam formed by the surface active proteins. Black gram starch and the mucilage together showed greater foam stability, probably due to enhanced viscosity caused by synergistic interactions between these polysaccharides. Gelatinization temperature as well as the peak and set back viscosities of wheat starch were considerably decreased by adding either the black gram or the linseed polysaccharide. In farinograph experiments the black gram polysaccharide exhibited a strengthening effect on wheat flour dough, whereas the linseed polysaccharide resulted only in an increased water absorption. Extensographic data indicated increased resistance and decreased extensibility of wheat flour dough by the addition of black gram and linseed polysaccharides.     

Rheological properties of wheat dough supplemented with functional by-products of food processing: Brewer’s spent grain and apple pomace

The physicochemical properties of brewer’s spent grain (BSG) and apple pomace (AP), and their effect on dough rheological properties were investigated. BSG had high protein content and both by-products were found to be high in dietary fibre. The rheological and the pasting properties of dough were significantly altered by the addition of by-products, with the main effects being due to the presence of dietary fibre. The biaxial extensional viscosity was significantly higher for the supplemented doughs; the strain hardening index decreased with increasing the levels of flour substitution. The replacement of wheat flour with the by-products significantly reduced the uniaxial extensibility, while the storage modulus, G″, was found to increase, indicating changes in the structural properties of dough. These changes were reflected in the ability of dough to rise during proofing.     

A comparison of the ability of several small and large deformation rheological measurements of wheat dough to predict baking behaviour

The rheological characteristics of twenty wheat flour samples obtained from four organic flour blends and a non-organic control were compared in relation to their ability to predict subsequent loaf volume in the baked bread. The flour samples considered had protein contents that varied between 11–14 g/100 g. Four different rheological methods were employed. Oscillatory stress rheometry on the protein gel extracted from the wheat flour, oscillatory stress rheometry and creep measurement on undeveloped dough samples and biaxial extensional measurements on simple flour–water doughs. None of the fundamental rheological parameters correlated with loaf volume. There was a correlation between the storage modulus of the gel protein and storage modulus for the undeveloped dough (r = 0.85). There was a weak negative correlation between protein content and biaxial extensional viscosity (r = −0.62). Stepwise multiple regression related loaf volume to dough stability time (measured on the Farinograph) and tan (phase angle) for the undeveloped dough samples (overall model r² = 0.54). The results indicate that the four rheological tests considered could not be used as predictors of subsequent loaf volume when the bread is baked.     

羧甲基化和乳化沙蒿胶对小麦粉的增筋作用

沙蒿胶可经羧甲基化和油基乳化提高水溶性和乳化性,其适用于小麦粉加工的增筋效果有待研究。本研究通过沙蒿胶的羧甲基化和乳化改性,分析其在小麦粉面团形成以及含油面团制作中的增筋效果。结果表明,羧基化改性可使沙蒿胶在小麦粉中的最佳添加量从1.0%降至0.4%,有效提高小麦粉的湿面筋量、面筋指数、吸水率、形成时间和稳定时间,降低弱化度,但在含油脂小麦粉中未表现出增筋性能的提升。与之对比,经小麦胚芽油或棕榈硬脂两种油相乳化处理的沙蒿胶则更适用于含油脂面团的调制,1.0%沙蒿胶和5%油脂以乳化方式添加,可降低液态和固态油脂在面团形成中的差异,并有效改善面团质构特性。本研究表明,羧甲基化可降低沙蒿胶应用于小麦粉增筋的使用剂量,而沙蒿胶乳化则适用于水油面团的增筋。     

不同品种紫薯粉面团品质特性

以纯小麦粉面团为对照,通过测定9种紫薯粉面团的粉质、糊化、流变学、水分分布状态特性,探讨9种紫薯粉对小麦粉混合面团品质特性的影响。结果表明:与纯小麦粉面团相比,不同品种紫薯粉面团的吸水率、稳定时间、弱化度、公差指数、糊化温度均有所增加;而面团带宽、峰值黏度、谷值黏度、最终黏度、衰减值、回生值均有所降低;储能模量、耗能模量和深层结合水基本呈现增加趋势,损耗角正切基本呈现下降趋势。紫薯粉的添加使得面团稳定性、保水性增加。不同紫薯粉平均粒径存在极显著性差异（P<0.01）,将紫薯粉平均粒径与其面团的粉质及糊化特性进行相关性分析和聚类分析,发现紫薯粉平均粒径与吸水率呈极显著正相关（P<0.01）,与稳定时间呈极显著负相关（P<0.01）;将紫薯粉面团分为三类,第I类包括鄂紫薯12号等7种紫薯粉面团;第Ⅱ类、第Ⅲ类分别为徐紫薯8号、绵紫薯9号。本研究为小麦粉面团专用紫薯粉品种的生产提供了理论依据。     

PHYSICOCHEMICAL, TEXTURAL AND NOODLE-MAKING PROPERTIES OF WHEAT DOUGH CONTAINING ALGINATE

The effects of the addition of alginate on the physicochemical, rheological and noodle-making properties of wheat flour were studied. The hydration properties (water absorption index, water solubility and swelling power) of wheat flour increased with increasing levels of alginate due to its high affinity to water. The addition of alginate caused increased water absorption and dough development time in the farinogram while the tolerance of dough to mixing was reduced. Also, the syneresis of the wheat flour gel was significantly reduced during freeze-thaw treatments when prepared with alginate. With the addition of alginate, the noodles exhibited an increase in the cooked weight and a decrease in the cooking loss. Moreover, the addition of alginate led to significant increases in the cutting and tensile forces of the noodles. In addition, the noodles containing more alginate exhibited lower lightness and redness, while yellowness was increased.

PRACTICAL APPLICATIONS

The purposes of this study are to examine the effects of alginate on the physicochemical and rheological properties of wheat flour dough and to evaluate its performance in noodle-making.
This study demonstrates that alginate can be used as a food additive to control and modify the rheology and texture of wheat flour products.     

Equibiaxial extensional flow of wheat gluten plasticized with glycerol

The aim of the present work has been to study the equibiaxial extensional flow of gluten/glycerol (60/40) mixture under lubricated squeezing flow with four different crosshead speeds at room temperature. The hyperelastic model with a strain energy potential of the Mooney–Rivlin form is applied to describe the biaxial stress as a function of strain at strains below 0.7. The strain rate thinning behavior of biaxial viscosity at constant strains is revealed.     

Rheological and sensory characteristics of doughs and cookies based on wheat,soybean, chick pea and lupine flour

Levels of 5, 10 and 15% of legume flours i.e. soybean, lupine and chick pea were used to supplement cookie. The effect of this supplementation on the rheological properties of the resulting dough was investigated using farinograph and extensograph as objective methods for quality assessment of the final product. It was found that there was an increase in water absorption capacity, dough stability, arrival time, dough development time and mix tolerance index. Extensograph results indicated that dough resistance to extension, dough energy and proportional number were minimized with increasing the lupine flour in the formula, while it was not changed on dough extensibility. However, soy flour increased resistance to extension, proportional number and energy and diminished dough extensibility. At the same time supplementing wheat flour with chick peas decreased both dough resistance to extension and proportional number while it increased dough extensibility and energy. For sensory evaluation, it was found that using either until 5% soybean or 10% chick pea or 15% lupine flour could replace the wheat flour in cookies formula without adversely affecting baking performance or altering the physical characteristics of the end product.     

Effect of native and germinated finger millet flour on rheological and sensory characteristics of biscuits

Wheat flour was replaced with native finger millet flour (NFMF) and germinated finger millet flour (GFMF) at 30–50% levels to make soft dough biscuits. Dough rheological properties and baking characteristics of the blends were evaluated. Farinograph data of wheat flour replaced with NFMF and GFMF showed a decrease in water absorption, dough stability and an increase in mixing tolerance index as the level of replacement increased. Extensibility of dough decreased for both NFMF and GFMF as the levels increased. The hardness of biscuit dough measured by texture profile analysis increased from 125 to 234 N for NFMF and 118 to 126 N for GFMF. Scanning electron microscopic studies on the biscuit dough showed polygonal finger millet starch granules adhering to wheat starch granules and protein matrix. The results of the study indicated that the replacement level of 40% with either NFMF or GFMF produced biscuits with acceptable sensory attributes. Addition of sodium stearoyl‐2‐lactylate (SSL) showed further improvement in terms of spread ratio, surface characteristics and texture.     

电子束辐照小麦粉的杀菌效果及对低菌小麦粉品质的影响

为减少有害微生物对小麦粉的污染,本文研究了电子束辐照对小麦粉的杀菌效果以及对其理化性质、流变学品质的影响。结果表明:电子束辐照处理可显著降低小麦粉中的微生物含量,且随着辐照剂量的增加,杀菌效果越显著;菌落总数、霉菌、酵母、蜡样芽孢杆菌、需氧芽孢菌的辐照杀菌剂量D10值分别为1.94、2.12、2.69、2.51和2.46 k Gy;剂量为1~5 kGy时,辐照对小麦粉基本营养成分及氨基酸含量无明显影响;辐照后小麦粉的湿面筋含量、面筋持水率也无明显变化,但面筋指数、降落数值随着剂量增加有所减小;辐照可提高小麦粉面团的吸水率,降低形成时间和稳定时间等;面团的拉伸面积、拉伸阻力和拉伸比例等面团流变学特性参数,均呈现先升高后降低趋势,但变化幅度很小。     

挤压膨化紫薯粉对小麦面团糊化特性和热机械学特性的影响

挤压膨化技术是一种高温、短时的加工方法,可以改变紫薯粉的特性,从而提高复合面团的品质。因此,本实验对紫薯粉进行挤压膨化,对比研究挤压膨化紫薯粉和紫薯生粉对小麦面团水分分布、糊化特性及热机械学特性的影响。结果发现,与紫薯生粉相比,挤压膨化紫薯粉显著缩短了横向弛豫时间T21（P＜0.05）,表明挤压膨化能够使水分与淀粉或面筋蛋白紧密结合;此外,与小麦粉相比,添加紫薯粉显著降低了面团的峰值黏度、谷值黏度、终点黏度、崩解值和回生值（P＜0.05）,尤其是挤压膨化紫薯粉。热机械学特性结果表明挤压膨化紫薯粉能够显著提高面团的吸水率、酶解速率和蒸煮稳定性（P＜0.05）,缩短面团形成时间,降低回生值和峰值扭矩（P＜0.05）。挤压膨化紫薯粉的添加不仅可以提高面制品的出品率,也有助于延缓面团的老化,延长保质期。本研究为挤压膨化紫薯粉在面制品中的应用提供了一定的理论依据。     

马铃薯全粉对比萨饼底加工工艺及品质的影响

研究马铃薯全粉对比萨面团流变学特性、发酵能力和比萨饼底质构特征、感官品质的影响。结果表明:马铃薯全粉能提高小麦粉的吸水率,缩短面团的形成时间,但会导致比萨面团的稳定时间缩短,弱化度增加;马铃薯全粉的添加量与面团的拉伸阻力、延伸度、最大拉伸比例和拉伸面积呈极显著负相关;马铃薯全粉能够提高面团的发酵能力和弹性,但会导致比萨饼底的硬度增加,感官品质略有下降,因此综合考虑确定马铃薯全粉的最佳添加量为15%;并进一步通过单因素和正交试验确定马铃薯比萨饼底的最佳原料配方为马铃薯全粉添加量15%、加水量60%、酵母添加量1.2%;在最佳原料配方的基础上确定马铃薯比萨的最佳工艺条件为醒发温度38℃、醒发湿度75%、醒发时间30 min、烘烤温度200℃、烘烤时间15 min,所得比萨的硬度为4 166.493 g,感官品质最佳。     

小麦粉吸水速率对面团特性及馒头品质的影响

该文以不同吸水速率的小麦粉为基础,研究在相同的揉混条件下,其面团特性及馒头品质的变化。使用粉质仪将面团稠度达到最高时所用的加水量与消耗的时间的比值定义为吸水速率,测定不同吸水速率小麦粉其粉质特性、湿面筋含量、面筋指数、游离巯基与二硫键含量、面团质构特性、馒头比容与高径比、馒头的质构特性。研究结果表明,当小麦粉吸水速率从0.17 g/s增大到3.87 g/s时,面团的稳定时间及粉质质量指数显著下降。其湿面筋含量从38.81%下降到19.19%,二硫键含量从13.31μmol/g下降到9.05μmol/g。面团的质构特性在发酵0 min时呈先升高后降低趋势、在醒发45 min后整体呈下降趋势。馒头的比容从2.67 mL/g降低到2.27 mL/g、高径比从0.68降低到0.56,其硬度、胶着性、咀嚼性均成下降趋势。整体而言,吸水速率低的小麦粉其面团相对较硬且馒头较为筋道有嚼劲;吸水速率较高的小麦粉其面团硬度稍弱且馒头较为松软。     

Emulsifiers: Effects on Quality of Fibre-Enriched Wheat Bread

Resistant starch (RS) is a nutritional ingredient commonly used in bread products as dietary fibre (DF). This ingredient presents similar physiological functions than those imparted by DF, promoting beneficial effects such as the reduction of cholesterol and/or glucose levels on blood. Quality improvement of bread containing RS, with an optimized combination of emulsifiers, will be useful in the development of new and healthy bakery products. The objective of this research was to analyse the effects of different emulsifiers on several quality parameters of dough and bread prepared with wheat flour partially substituted with resistant starch as a dietary fibre. A blend of wheat flour/maize-resistant starch (MRS; 87.5:12.5) with sodium chloride, ascorbic acid, α-amylase, compressed yeast and water was utilized. Emulsifiers were incorporated to formulations in different levels according to a simplex centroid design. The viscoelastic, textural and extensional properties of dough were analysed. Bread quality was evaluated throughout the gelatinization and retrogradation of starch, specific volume of loaves, and texture and firmness of bread crumb. The incorporation of 12.5% (w/w) of MRS to wheat flour caused an increase of 5% in water absorption. Stability decreases markedly (from 9.9 to 2.2 min) and the mixing tolerance index increased (from 79 to 35 UF). The sodium stearoyl lactylate (SSL)–diacetyl tartaric acid esters of monoglycerides (DATEM) mixture increased hardness and resistance to extension on dough, whilst dough containing Polysorbate 80 (PS80) was softer; nevertheless, both types of dough retained less CO₂. An optimized concentration of the three emulsifiers (0.24% SSL, 0.18% PS80, 0.08% DATEM, w/w) was obtained by surface response methodology. The bread prepared with this combination of emulsifiers presented a considerable specific volume with a very soft crumb.     

茶叶蛋白质对面团流变学特性的影响

为探索茶蛋白作为添加剂在面制品中应用的可行性,以市售小麦粉为原料,添加不同比例的茶叶蛋白质置于小麦粉中,通过粉质实验和拉伸实验,研究其对小麦粉面团流变学特性的影响。结果表明:粉质特性参数中,随着茶叶蛋白质添加量的增加,面团吸水率增加,形成时间和稳定时间降低,弱化度增加;拉伸实验中,随着添加量的增加,面团拉伸比例、延伸度、拉伸阻力先增加后减小。     

小麦面粉蛋白质特性和面团流变学特性的关系

目的探究小麦面粉蛋白质理化特性与面团流变学特性之间的关系。方法以19份抗旱节水鉴定品种小麦籽粒为试验材料,测定了蛋白质、湿面筋、谷蛋白大聚体含量、沉降指数等面粉蛋白质理化特性,以及粉质参数和拉伸参数等面团流变学特性,采用通径分析研究了面粉蛋白质理化特性与面团流变学特性的关系。结果面粉蛋白质含量对面团吸水率直接增强效应较大,但对稳定时间、拉伸长度的抑制效应较大;谷蛋白大聚体含量对形成时间、最大拉伸阻力、拉伸面积的直接增强效应和综合增强效应均较大;沉降指数对稳定时间和最大拉伸阻力、拉伸面积的直接增强和综合增强效应较大;所测蛋白质理化特性中未发现对拉伸长度有增强效应的指标。结论面粉中谷蛋白大聚体含量和沉降指数是对面团形成时间、稳定时间、拉伸阻力影响较大的因素,影响为正效应,可为专用面粉生产质量控制提供参考。