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.     

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.     

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。     

EFFECT OF MINERAL FORTIFICATION ON RHEOLOGICAL PROPERTIES OF WHOLE WHEAT FLOUR

This study was aimed to evaluate the rheological changes that take place in the dough as a result of addition of elemental iron, ferric sodium ethylenediaminetetraacetate, zinc sulphate and zinc oxide in various combinations to whole wheat flour (WWF), packaged in polypropylene woven bags and tin boxes and stored for a period of 60 days under ambient and controlled conditions of temperature and relative humidity. Water absorption (WA) capacity, dough development time (DDT) and dough stability time (DS) of the fortified WWF were measured by farinographic method, and peak viscosity was assessed by viscographic analyses. WA capacity and DDT of flours increased during storage. Fortification significantly (P  <  0.05) affected WA, DDT, DS and viscographic characteristics of the flours. Packaging materials (P  <  0.05) influenced WA, DDT and DS, while storage condition had only affected viscographic properties of the flours.

PRACTICAL APPLICATIONS

The success of any fortification program depends on the stability of micronutrients and food to which they are added. Exposure of the fortificants to any of the physical and chemical factors including heat, moisture, air, or light and acid or alkaline environments during food processing, packaging, distribution or storage affects their stability. The rheological properties of dough made from fortified flours determine the quality of the fortified end product. Changes in rheological properties as a result of the incorporation of fortificants in the flour, its storage under variable conditions and length of time might have an effect on quality, cost and nutrition of the product.     

THE EFFECT OF TEMPERATURE ON SOME RHEOLOGICAL PROPERTIES OF WHEAT FLOUR DOUGHS

Abstract. Doughs from three flours were sheared between a cone and plate at constant rates in the range 6 times 10^-4-2 times 10^-2 s^-1.
At temperatures between 25 and 40C, the apparent viscosity decreased with increasing temperature and with increasing rate of shear. The effects of the temperature and of the rate of shear were independent one of another, and can be described by an Arrhenius type equation and a power equation, respectively. At temperatures between 45 and 60C, the apparent viscosity increased rapidly with increasing temperature; this is ascribed to starch gelatinization. In this temperature range, the apparent viscosity decreased more rapidly with increasing rate of shear than at lower temperatures.
At temperatures between 25 and 45C, the shear modulus decreased with increasing temperature and slightly increased with increasing rate of shear. From the former fact it is concluded that the elasticity of dough has an origin different from rubber elasticity. In this temperature range, the shear modulus can be described by an equation similar to that for the apparent viscosity. At temperatures between 45 and 65C, the modulus increased with increasing temperature, though to a lesser extent than the apparent viscosity.
Changes in the rate of stress relaxation are in accordance with the effects of temperature and rate of shear on the apparent viscosity and the modulus.     

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.     

USE OF NONLINEAR DIFFERENTIAL VISCOELASTIC MODELS TO PREDICT THE RHEOLOGICAL PROPERTIES OF GLUTEN DOUGH

Nonlinear viscoelastic models of the differential type, such as the Phan Thien Tanner model, White‐Metzner model and Giesekus model were used to predict the steady shear, oscillatory shear and transient shear properties of gluten dough. The predictions were compared with new data and the experimental results of Wang and Kokini (1995b). The Phan‐Thien Tanner model and the Giesekus model were used in eight modes to fit the relaxation modulus accurately. The White‐Metzner model gave the best prediction for the steady shear properties as it used a Bird‐Carreau dependence for the shear viscosity. The Phan‐Thien Tanner model and the Giesekus model predicted the transient shear viscosity and the transient first normal stress coefficient better than the White‐Metzner model. A consistent prediction of all the experimental data could not be obtained using a single model.     

小麦面筋蛋白结构、功能性及应用

小麦面筋蛋白的结构和组成是影响小麦粉面团粘弹性及烘焙品质的重要因素，而且在食品和非食品领域有着广泛的应用。对小麦面筋蛋白的结构、组成对功能特性的影响进行了综述，并简要介绍了小麦面筋蛋白在食品方面的应用。     

酶法降解小麦面筋蛋白制备抗氧化产物的研究

采用12种不同来源、不同性质的蛋白酶对小麦面筋蛋白进行酶解改造，通过考察水解液体外抗氧化活性、酶解蛋白的水解度和回收率等指标，筛选最适降解小麦蛋白的蛋白酶。结果表明：木瓜蛋白酶（精）效果最佳，其酶解蛋白含量为2．81％，回收率为76，60％，水解度为58．22％，经稀释5倍后的DPPH自由基的清除率为76．5％，还原力为3，00％。     

THE EFFECT OF HEAT AND SHEAR ON THE VISCOELASTIC PROPERTIES OF SOY FLOUR DOUGH

This paper is concerned with the effect of heat and shear on the rheological properties of defatted soy dispersions and doughs of 30 to 60% flour by weight. Capillary and rotary rheometers (Rheometrics Mechanical Spectrometer) were used to heat doughs up to 75° C and shear them simultaneously. In one series of experiments using a modified Instron capillary rheometer the doughs were heated to several different temperatures and then sheared. The linear viscoelastic properties of the dough which were determined by means of a plate-plate rheometer were then compared to the fresh dough and those of a heated but nonsheared dough. In another experiment a cone-and-plate rheometer was used to heat and shear the dough. The linear viscoelastic response of the dough was used to monitor any changes as it was heated and sheared. It was observed that only in the higher moisture dispersions (i.e., moisture contents greater than 50%) were there any signs of an increase in rheological properties which might be associated with “cooking”. It was concluded that cooking of soy flour doughs most likely does not involve the formation of a permanent network formed by covalent chemical bonds. Hence, in extrusion cooking processes involving soy flour doughs, it may not be necessary to treat the rheological properties of the dough as a thermosetting system.     

EFFECT OF APPLE POMACE INCORPORATION ON RHEOLOGICAL CHARACTERISTICS OF WHEAT FLOUR

Different levels of apple pomace with different particle size at each level were blended with wheat flour as a source of dietary fiber and the blends were evaluated for their rheological characteristics. Farinographic water absorption increased from 59.1 ml in control to 69.4, 68.2 and 70.2 ml in blends with 11 percent pomace of 30, 50 and 60 mesh, respectively. Wheat flour took 1.9 min. for dough development and the corresponding values for blends containing 11 percent of 30, 50 and 60 mesh pomace were 3.9, 3.8 and 3.8 min., respectively. Mixing tolerance of the blends with 11 percent of 30, 50 and 60 mesh pomace increased to 85.0, 92.5. and 97.5 BU as against 67.5 BU in case of control (wheat flour). Dough stability increased slightly upto 8 percent pomace level but decreased at higher levels of pomace. Gelatinization temperature did not show any remarkable change with pomace incorporation upto 11 percent. Peak viscosity decreased when pomace level was increased from 0 (control) to 5 percent but thereafter it increased. Temperature at peak viscosity did not show much variation between the blends.     

EFFECTS OF EMULSIFIERS ON DOUGH RHEOLOGICAL PROPERTIES AND THE TEXTURE OF EXTRUDED NOODLES

The effects of six emulsifiers on the rheological properties of wheat flour doughs were evaluated using capillary and oscillatory rheometers. Sodium stearoyl 2-lactylate (SSL) and sucrose fatty acid ester 160 (SFAE 160) significantly increased the apparent viscosities (η), storage moduli (G") and loss modulus (G") of the doughs. The η, G' and G" increased with the concentrations of SSL from 0.5 to 1.5%. Lecithin, SFAE 110 and 20W (low HLB values) had the opposite effects. Extruded noodle with SSL had the highest tensile strength and cutting force among all treatments. Therefore, SSL could be used to produce the extruded noodles with higher elasticity. Lecithin, MG, SPAE 110 and 20W decreased the strength of the extruded noodles. There was a positive correlation between viscosity and shear modulus of the doughs and the strength of extruded noodles. Values of HLB emulsifiers used in this study were positively correlated with G' and η*.     

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.