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.     

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.     

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。     

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.     

PHYSICAL PROPERTIES OF SUGAR-SNAP COOKIES USING GRANULE SURFACE DEPROTEINATED WHEAT STARCH

The physical properties of soft wheat starch granule surface proteins and soy flours or isolates, which contribute to the texture of sugar‐snap cookies was studied. Soft wheat flour was deproteinated and cookies were produced containing 0, 10, 20 or 30% soy flour, or one of two types of ground, textured soy flour. Color, fracture force and spread ratio of cookies were determined. Cookies formulated with wheat starch stripped of the starch granule surface proteins exhibited significant alterations in diameter, fracture force, thickness and surface cracking. Cookies containing ground, textured soy flour and protein‐stripped starch granule wheat flour were larger, thinner and had more surface cracking than those produced with nontextured soy flour. Wheat starch granule surface proteins appear to partially mediate the interaction of proteins and starch in a sugar‐snap cookie system.     

WATER ABSORPTION EFFECTS ON BIAXIAL EXTENSIONAL VISCOSITY OF WHEAT FLOUR DOUGH

Biaxial extensional viscosities of wheat flour dough at three water absorption levels were determined as a function of biaxial strain rates using lubricated squeezing flow. The shape of the curves obtained in this study showed a sharp increase followed by a gradual increase which could indicate the presence of viscoelastic effects, which is not the usual case reported in the published literature for other products when using this technique. Plasticizing effect of water coupled with the effect of the starch and the interaction among the other components of wheat flour dough could explain the rheological behavior of flour dough during lubricated squeezing flow testing. Values of biaxial extensional viscosities of wheat flour dough for the three water absorption levels obtained in this study showed significant differences in the entire deformation range (P < 0.05).     

THERMAL DIFFUSIVITY MEASUREMENTS of WHEAT FLOUR and WHEAT FLOUR DOUGH

A simple technique was used to measure thermal diffusivity of whole wheat flour and whole wheat flour dough at various levels of moisture and temperatures. the experimental values showed good agreement with the calculated values. It was found that thermal diffusivity of dough increases with moisture and temperature below 60C, but above 60C its value decreases. This is attributed to physico-chemical changes, e.g., starch gelerinization and protein coagulation. Due to these changes swelling and softening of dough occur, which reduce the ability of dough to diffuse thermal energy, thus lowering the value of the thermal diffusivity. Based on the experimental value of wheat dough at various moisture levels and temperatures, the following equation is proposed: α= (7.957 − 0.6346 M + 0.217 T + 0.008 M²− 0.00176 T²− 0.00051 M × T) × 10-7     

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.     

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.     

RHEOLOGICAL BEHAVIOUR OF MIXED GELS OF WHEAT STARCH AND ETHYL(HYDROXYETHYL)CELLULOSE

Gelatinisation of wheat starch (6%) in the presence of a nonionic amphiphilic polymer, ethyl(hydroxyethyl)cellulose (EHEC) has been studied. Concentration (0.1–1 wt %) and molecular weight (approximately 80,000–350,000) of EHEC were shown to influence the rheological behaviour of the pastes at 60C, and the gels after 340 min storage at 25C. Two separated regions in the mechanical spectra (0.01–10 Hz) were observed for the mixed gels at 25C with the highest concentration of EHEC. This behaviour suggested long range (overall gel properties) and the influence of short range (molecular entanglements) interactions.     

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.     

浅谈粉厂小麦水分调节对面粉质量的影响

阐述了粉厂小麦水分调节的重要性，影响水分调节的因素和小麦水分调节的方法。针对国内粉厂的现状，提出了解决北方粉厂冬季润麦不透这一难题的方法。     

EFFECT OF ADDITIVES ON RHEOLOGICAL CHARACTERISTICS AND QUALITY OF WHEAT FLOUR PAROTTA

Effects of oxidizing agents (potassium bromate [20 and 40 ppm], ascorbic acid [100 and 200 ppm] and potassium iodate [20 and 40 ppm]), reducing agents (potassium metabisulphite [100 and 200 ppm] and cysteine hydrochloride [50 and 100 ppm]), enzymes (fungalα‐amylase [10 and 20 ppm] and protease [10 and 20 ppm]) and dry gluten powder (1, 2 and 3%) on rheological characteristics of dough and quality of parotta were studied. Addition of oxidizing agents and dry glutenincreased values for farinograph stability, extensograph and mixograph areas, apparent biaxial extensional viscosity, compressive stress, hardness and cohesiveness, while reducing agents and enzymes decreased the aforementioned characteristics and increased force decay parameter and adhesiveness of the dough. Among the different additives studied, incorporation of 100‐ppm potassium metabisulphite, 50‐ppm cysteine hydrochloride and 10‐ppm protease increased the overall quality score of parotta.