PUNCTURE AND STRESS RELAXATION BEHAVIOR OF BLACKGRAM (PHASEOLUS MUNGO) FLOUR-BASED PAPAD DOUGH

Papad is a popular traditional food adjunct in South East Asian countries. The rheology of papad dough is important for the purpose of sheeting and/or rolling. In the present study, two methods for testing the behavior of papad dough (prepared from blackgram flour) have been presented and correlated with the instrumental stickiness values. These consist of an empirical method (puncture testing) and a fundamental procedure (stress relaxation characteristics). In the former method maximum stress during compression was used as an index. In the later method, the parameters determined included the stress decaying constants k₁ and k₂, the percent relaxation and the initial compressive stress. These tests were conducted on the papad dough with varying moisture content (32–40%) and at different dough holding (resting) times (0–120 min). Stickiness values in the range of 141 and 148° were suitable for machining of the dough to make flat circular papad sheets. The corresponding moisture content was between 35 and 36% when the holding time was in the range of 0-30 min.     

变性淀粉及谷朊粉对面团特性的影响研究

研究淀粉及变性淀粉、谷朊粉对面团特性的影响。结果显示：在面粉中，按4％的比例添加马铃薯变性淀粉，对面团的稳定时间、弱化度及抗张强度等均有显著的影响（P〈0．01）；添加6％木薯变性淀粉，面团抗张力增加26、6％；添加3％的谷朊粉，面团形成时间及稳定时间均有较大增加。木薯原淀粉及其变性淀粉等对面团的特性影响不大。     

苦荞小麦混和粉面团的粉质和拉伸特性

用粉质仪和拉伸仪测定了苦荞小麦混和粉面团的流变学性质。结果表明:含有天然苦荞混和粉(30∶70)的面团,稳定时间下降4.1min,最大拉伸阻力增加239BU,延伸性下降20mm;含有处理苦荞小麦混和粉(30∶70)的面团,稳定时间增加0.9min,最大拉伸阻力和延伸性分别下降190.5BU和30.1mm;0.01%的转谷氨酰胺酶、葡萄糖氧化酶或脂肪酶均能提高混和粉的最大拉伸阻力,降低其延伸性;0.002%戊聚糖淀粉酶减少面团的最大抗拉伸阻力,增加面团的延伸性;葡萄糖氧化酶与戊聚糖酶淀粉酶合用,处理苦荞小麦(30:70)混和粉面团的最大抗拉伸阻力增加148.5BU,延伸性不降低。     

INFLUENCE OF NATIVE LIPIDS ON THE RHEOLOGICAL PROPERTIES OF WHEAT FLOUR DOUGH AND GLUTEN

We report on the viscoelastic properties of dough and gluten (prepared by ultracentrifugation) after the flour lipids had been removed by solvents differing in polarity (chloroform, ethanol and diethylether). The extracted lipids were fractionated by thin layer chromatography. The flours differed in lipid composition after the extraction. Ethanol removed more polar lipids than the other solvents. Removal of lipids (0.6–0.9% on flour weight) altered the viscoelastic properties of dough significantly, whereas those of gluten were only marginally affected. The storage modulus (G′) of dough increased with used solvent polarity. The highest value of G′ was observed for the dough made with the flour where the lipids were removed by ethanol. This was consistent with a marked decrease in the frequency dependence of G′ of dough when the lipids were removed.     

EFFECTS OF MOISTURE,SUCROSE, NaCl,AND ARABINOXYLAN ON RELAXATION IN WHEAT DOUGH AS MEASURED BY DMTA

The effects of sucrose, NaCl, and arabinoxylan on the α-relaxation of wheat doughs with different water contents were investigated using Dynamic Mechanical Thermal Analysis (DMTA). DMTA measurements were made at the heating rate of 2°C/min from at least 30°C below the observed onset of the α-relaxation (glass transition) to at least 30°C above the transition. The glass transition temperature, T_g , was taken from the onset temperature of the decrease in storage modulus (G′). The frequencies used were 0.1, 1, and 5 Hz and amplitude was 16 μm. The storage modulus, G′, showed α-relaxation in all doughs with added ingredients. Added ingredients decreased the glass transition temperature of dough. The T_g of doughs with different ingredients decreased with increasing water content of doughs over the whole a_w range used (0.113–0.753). Also, the T_g increased with increasing frequency.     

关于一类模糊积分方程解的存在唯一性

利用Ｆｕｚｚｙ压缩映象的不动点定理证明了一类线性Ｖｏｌｔｅｒａ型Ｆｕｚｚｙ积分方程ｆ（ｘ）＝φ（ｘ）＋λ∫ｘｘ０Ｋ（ｘ，ｔ）ｆ（ｔ）ｄｔ解的存在唯一性定理．     

RHEOLOGY AND MICROSTRUCTURE OF WHEAT DOUGH DEVELOPED WITH CONTROLLED DEFORMATION

Undeveloped wheat dough samples were strained in shear and extensional flow between parallel plates to produce a controlled level of development. Dough made in a standard Farinograph, considered developed dough, was used for comparison. Scanning electron microscopy images of deformed dough were subjected to numerical image processing to characterize the protein matrix present. Results were compared to dynamic rheological properties to evaluate the influence of strain deformation on the formation of microstructure. Viscoelastic moduli of wheat dough showed that developed dough had the greatest amount of structure formation, followed by extensionally-strained and shear-strained samples, respectively. Undeveloped dough showed the lowest levels of structure development. Image analysis indicated statistically significant differences between protein matrices in developed and undeveloped samples; however, results were not significantly different between shear- and extension-ally-strained samples.     

INFLUENCE OF HYDROXYPROPYL METHYLCELLULOSE ON THE RHEOLOGICAL AND MICROSTRUCTURAL CHARACTERISTICS OF WHOLE WHEAT FLOUR DOUGH AND QUALITY OF PURI

Puri is a traditional unleavened fried product prepared from whole wheat flour. Hydroxypropyl methylcellulose (HPMC) was used to study its effect on rheological characteristics of whole wheat flour dough and puri making quality. Addition of HPMC at 0.5 and 1.0% w/w increased the water absorption and dough stability whereas the resistance to extension and extensibility decreased. Pasting temperature, peak viscosity and cold paste viscosity gradually decreased. The moisture and fat contents of puri increased marginally. Quality parameters and sensory acceptability were monitored after 0 and 8 h of storage. Addition of 0.5% HPMC gave higher sensory scores. Microscopic observations during puri processing showed that the starch granules in the control dough were clearly visible in the protein matrix, which reduced on frying due to partial gelatinization. Microstructure of puri with HPMC showed higher gelatinization of starch. It also helped in moisture retention and hence, resulted in highly pliable and soft-textured puri .

PRACTICAL APPLICATIONS

Puri is a traditional unleavened fried product that is prepared by mixing whole wheat flour and water, sheeted to a desirable thickness and fried. Use of hydroxypropyl methylcellulose (HPMC) affected the whole wheat flour dough and puri making quality. It helped in moisture retention and hence, resulted in highly pliable and soft-textured puri . Microstructure of puri with HPMC showed higher gelatinization of starch.     

EFFECT OF REPLACEMENT OF SUGAR WITH SUCRALOSE AND MALTODEXTRIN ON RHEOLOGICAL CHARACTERISTICS OF WHEAT FLOUR DOUGH AND QUALITY OF SOFT DOUGH BISCUITS

ABSTRACT

The effect of replacement of 30% sugar with 0.05% sucralose and of different levels of maltodextrin (MD) on dough rheology and quality of biscuits was studied. The results showed that replacement of sugar with increasing amount of MD from 10 to 40% along with 0.05% sucralose influenced dough rheology. The farinograph water absorption increased up to 20% addition of MD and thereafter decreased. Objective evaluation of biscuits showed that the spread ratio of biscuits with 10% MD was 7.1, 20% MD was 7.8, 30% MD was 9.4 and 40% MD was 10.5, in comparison to control biscuits (9.9) with 30% sugar. The best overall quality score was reported for the control biscuits with 30% sugar, 69 out of the maximum score of 80, followed by 30% MD (65), 40% MD (60.5), 20% MD (54) and 10% MD (49.5). The results showed the possibility of replacing sugar in biscuit with sucralose and MD.

PRACTICAL APPLICATIONS

This article discusses the changes as a result of replacement of sugar with sucralose and maltodextrin (MD) in the rheological characteristics of wheat flour dough. The level of sucralose and MD required to replace sugar from control recipe in order to produce rheological characteristics of wheat flour dough comparable with that of the control has been highlighted in the article. This information will have a practical application in the production of sugar‐free soft dough biscuits.     

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.     

INFLUENCE OF THE STARCH GRANULE SURFACE ON THE RHEOLOGICAL BEHAVIOUR OF WHEAT FLOUR DOUGH

The influence of the properties of the starch granule surface on the rheological behaviour of wheat flour doughs was studied in dynamic oscillation measurements (frequency sweep and strain sweep) and in stress relaxation measurements. A flour with a high protein content (15%) was diluted with wheat starch to obtain a protein content of 10%. The granule surface of the substituted starch was modified in three different ways: by heat treatment, by adsorption of a wheat protein fraction and by adsorption of lecithin to the granule surface. The effects of these modified starches were compared with the results obtained for nonmodified starch and protein or lecithin (in liposomes) added to the flour. Owing to the low concentration of the added protein and lecithin, no effect was observed when they were added to the bulk of flour. However, as a starch-surface modification the same components influenced the rheological parameters studied. Also the heattreated starch had an effect on the rheological behaviour. The study established the importance of the properties of the starch-granule surface in wheat flour dough.     

馒头面团发酵性能的研究

通过研究发酵过程中面团pH值和体积的变化,分析酵母、糖和食盐对馒头面团整个发酵过程的影响.结果表明.酵母、糖和食盐对面团的发酵速度和发酵体积均有影响.面团的发酵速度随着酵母的增加而加快,但面团的持气性却随着酵母的增加而下降;糖对面团的发酵有一定的促进作用,但过量的糖对面团的持气性却有一定的破坏作用;食盐对面团的发酵有一定的抑制作用.但适量的食盐面团的持气性有着一定的改善作用.     

APPLICATION OF A VISCOMETRIC METHOD TO THE STUDY OF WHEAT FLOUR DOUGHS*

The cone and plate viscosimeter was found applicable to studying the effect of experimental variables on the behaviour of flour doughs. A simple method of analysis based on the use of a power law is proposed. The variables studied were: type of flour, water content, mixing time, temperature and the presence of certain chemical compounds. Based on the results obtained, hypotheses were advanced on the importance of non-covalent bonds in influencing the rheological properties of doughs.     

SLIT RHEOMETER STUDIES OF WHEAT FLOUR DOUGH1

Rheological properties of bread dough having different levels of added gluten (0, 2.5, 5.0 and 7.5%) were measured. The dough was forced through a slit die attached to a cylindrical container. The material functions of interest included steady shear viscosity, first normal stress coefficient in steady shear flow derived from hole pressure measurements and planar extensional viscosity as estimated from entrance pressure drop measurements. These rheological properties were correlated to the loaf volume of the baked bread. Results indicate that the first normal stress coefficient and planar extensional viscosity were affected by the gluten content of the dough and correlated well with the loaf volume. The entrance pressure drop increased with increasing apparent shear rate but entrance correction was found to decrease with apparent shear rate. Water had a greater effect on the rheological properties than gluten content. The Trouton ratio was rather large and ranged between 850 to 2000 at a strain rate of 1s^-1 and decreased with increasing extension rate for most cases.     

小麦胚芽的提取与利用

叙述了小麦胚芽的提取与干燥过程,及其作为添加剂及营养强化剂等方面的应用。     

INFLUENCE OF GUMS ON DOUGH PROPERTIES AND FLAT BREAD QUALITY OF TWO PERSIAN WHEAT VARIETIES

The effects of separate mixing of two hydrocolloids carboxymethylcellulose (CMC) and hydroxypropylmethylcellulose (HPMC) at 0.1, 0.3 and 0.5% levels with Sardary and Sorkheh wheat flours (two native Persian varieties) were studied. Chemical and rheological (Farinograph and Extensograph) tests, staling and sensory evaluations were performed on the two flours, their dough and the resulting Lavash flat bread, respectively. On the basis of split‐plot experiment in a complete random design and using the Duncan's multiple range tests, the data were evaluated and the average of replicates was compared at the statistical level of 1% (α = 0.01). Although the CMC and HPMC gums enhanced significantly the dough quality of the two wheat varieties by increasing water absorption and reducing resistances after 90 and 135 min (compared with control), the effect of HPMC was more pronounced than CMC. Anti‐staling properties of HPMC were better than CMC, especially for Sardary flour. Separate addition of 0.5% CMC and HPMC gums to Sorkheh and Sardary flours significantly delayed the staling process of the resulting Lavash bread by more than 45 and 42%, respectively. Additionally, sensory evaluation scores of the Lavash bread made from either Sorkheh flour containing 0.3% CMC or HPMC or Sardary flour containing 0.5% HPMC were 50 and 120% higher than control bread samples, respectively.