Fatty acids composition and rheology properties of wheat and wheat and white or brown rice flour mixture

Manufacturing of bread from rice flour only presents technological difficulty because the rice is gluten-free and gluten is the most important structure forming protein. By using wheat and rice flour mixture, this problem can be avoided, and end product is enriched by rice-oil constituents. In this paper fatty acids composition, with an emphasis on total saturated, and total unsaturated fatty acids, rheological and baking properties of wheat–rice flour mixture (70:30 w/w) were investigated. The results show that wheat–rice flour mixture has better fatty acids composition with higher content of stearic, arachidic, lignoceric, oleic, and phthalic acids compared to wheat flour. Also, wheat flour did not include myristic, arachidic, lignoceric and linolenic acids, so rice flour addition made fatty acids profile richer as number of constituents is higher, nine instead six. The content of total unsaturated fatty acids content was higher in wheat–brown rice flour mixture than in wheat flour and in wheat–white rice flour mixture. When rice flour was added to wheat flour the rheological properties were changed: flour mixture had less water absorption, less degree of softening, longer development time, higher gelatinization temperature, but better stability and finally, better quality number and group than wheat flour. So, the wheat and rice flour mixture can be considered as a good quality flour and can be used for making good quality wheat-rice bread and cake.     

Staling of cake prepared from rice flour and sticky rice flour

MiGao, prepared from rice flour and sticky rice flour, is a kind of steam cooked Chinese cake. Staling of MiGao resulted in loss in texture and eating quality. Moisture content, water activity, texture, differential scanning calorimetry thermograms and sensory quality of MiGao, were monitored and were found to be significantly affected by cake staling when stored at room temperature for up to 5 days. The moisture content decreased after 2 days of storage and during the following days the crumb moisture content remained practically unchanged. Firmness was developed mainly during the first day of storage, remained at a similar level from day 2 to 3 and increased slightly after the third day of storage. A decrease in sensory quality and acceptability of the MiGao was observed during storage. Differential scanning calorimetry was used to follow changes of starch retrogradation in MiGao crumb. Amylopectin recrystallisation in MiGao continued to increase during storage.     

月饼粉专用小麦的研究

对河南信阳小麦样品进行理化性质及食用品质测定分析,并制作月饼进行感觉评价和月饼面团制作工艺性能比较,从而筛选出一些适宜于制作月饼专用粉的小麦品种,为下一步制作月饼专用粉打下基础.     

Rheological characterisation of cake batters generated by planetary mixing: Comparison between untreated and heat-treated wheat flours

The rheological behaviour of high ratio cake batters prepared with untreated and heat-treated wheat flours was analysed at different stages of the manufacturing process, namely slurry, (on aeration) foams and (with fat addition) aerated emulsions, featuring air volume fractions up to 0.50. Both steady shear and viscoelastic behaviours were studied. All materials exhibited shear-thinning behaviour at 20 °C over the shear rate range studied (0.07-10 s⁻¹). The generalised Cox-Merz rule could be applied to all samples. Materials prepared with heat-treated flours exhibited greater stability, as indicated by slurry thixotropy and cohesive energy, and the change in apparent viscosity and air content of foams and aerated emulsions on extended mixing. Foams and aerated emulsions showed significant elastic behaviour with G′∼G″. The temperature dependency of aerated emulsions was studied by oscillatory shear testing from 20 to 100 °C and indicated three regimes in temperature dependence: below 40 °C G′and G″ were insensitive to temperature; between 40 and 70 °C the complex viscosity exhibited Arrhenius-type behaviour, while above 70 °C G′ and G″ increased as expected for gelatinisation and foam setting. The weak gel model for foods was used to analyse the latter data sets and confirmed that the gel network generated in aerated emulsions prepared with heat-treated flours was significantly stronger than those made with unheated flours. The differences between flour types were also observed in tests on un- and heat-treated flours obtained from a second and third harvest. The impact of these quantifiable differences in rheology on performance during baking is discussed.     

Effect of rice variety,rice flour concentration and enzyme levels on composite bread quality

A study was conducted to determine the suitability of substituting portions of wheat flours with rice flours for breadmaking. The levels of substitution were 50, 100, 150 and 200 g kg^?1. Two kinds of enzymes, barley malt and fungal amylase, were added to composite flours, and their effects on the volume and quality of the rice-based bread were determined. The results showed that the enzymes, levels of replacement and the varieties of rice had significant effects on weight, specific volume and overall acceptability of the bread samples. However, the enzymes did not have significant effects on the volume, protein and fat contents or on the character and color of the crust in the sensory analysis. Comparisons were made of the nutritional and sensory qualities of the bread made entirely from wheat flour, and the sample which performed best, the bread with 50 g kg^?1 of flour from low amylose variety (183.3 g kg^?1) with barley malt, showed non-significant differences. The overall acceptability of the products showed that it is acceptable to substitute wheat flour with flours generated from rice up to the 150 g kg^?1 replacement level only.     

The effects of xanthan and guar gums on staling of gluten-free rice cakes baked in different ovens

The objective of this study was to determine the effects of different concentrations of xanthan and guar gums and their blends on staling of gluten-free rice cakes baked in microwave-infrared combination oven (MW–IR) and to compare the cakes with conventionally baked ones. Gums were added at concentrations of 0.3% and 1.0%. For preparation of gum blend, 0.5% xanthan gum was mixed with 0.5% guar gum. In order to understand the staling behaviour of cakes, cakes were stored at 22 ± 2 °C for 120 h. Xanthan-guar gum blend decreased hardness, weight loss, retrogradation enthalpy and the change in setback viscosity values of cakes during storage for both types of ovens as compared to control formulation. It was found that oven type was a significant factor in affecting staling parameters of gluten-free cakes.     

Contribution of lipid to physicochemical properties and Mantou-making quality of wheat flour

Defatted flours of wheat varieties Karl and Jagger, after removing lipids by chloroform, were used to investigate the contribution of lipid to physicochemical properties and Mantou-making quality by comparing microstructure and thermal properties. The results indicated that defatted flours tend to have more single starch granules, higher gelatinization enthalpy, more water absorption, longer pasting peak time, higher peak and hold viscosity, lower setback and breakdown than those of the control. Meanwhile, the defatted flours had improved cooking stability and better ability to withstand mechanical shear stress. The Mantou-making test showed that the volume of Mantou made from defatted flour did not change significantly. C-Cell analyses on the internal crumb grains of Mantou revealed a deterioration in crumb grain characteristics upon removal of lipids from the flours. The grain cells of Mantou became bigger with thicker cell walls upon removal of lipids.     

不同粉路中的小麦粉及其淀粉性质测定

研究了1T下、3M下、1Sf小麦粉及其淀粉的性质,测定了其淀粉、蛋白质、灰分、水分以及直链淀粉的含量,并对淀粉的粒径分布、溶解度和膨润力以及淀粉糊的透明度、冻融稳定性等特性进行了分析。实验结果表明:在小麦胚乳结构中,越接近麦心的部位,淀粉和直链淀粉含量越高,水分和蛋白质含量越低,灰分的差异不大;淀粉颗粒的大小顺序为3M下>1Sf>1T下,粒径呈正态分布;小麦淀粉随温度的升高,溶解度增大,膨润力上升;小麦淀粉糊的透明度较高,冻融稳定性较差。     

制粉过程中各系统面粉流变学特性的研究

在生产面包及饼干专用粉的制粉过程中,粉路各系统不同出粉部位面粉的流变学特性呈现出明显的差异,这为粉流选择性混配提供了条件,使粉路在线配粉成为可能。研究表明,面包专用粉宜选择皮磨、渣磨、中路心磨及一部分前路心磨的面粉,饼干专用粉选择前路皮磨、前路渣磨及一部分心磨的面粉进行混配,由此能够配制出质量稳定的优质专用粉。     

A bench-scale high-shear wet-milling test for wheat flour

Bench-scale wet-milling tests for wheat flour are available for the traditional processes of Martin and Batter, but tests for the high-shear processes of Alfa-Laval/Raisio, Hydrocyclone, and High-Pressure Disintegration are few in number. In this study, critical processing parameters of a high-shear wet-milling process, namely high-shear mixing, gluten-aging, and gluten-washing steps, were investigated using response surface methodology, and those parameters led to a bench-scale wet-milling test starting with a “highly sheared flour–water dispersion” (HS-FWD). Optimum conditions for the test were: a water–flour ratio (db) of 1.7, water temperature of 35 °C, and homogenizer speed of 6000 rpm for 2.0 min in the high-shear mixing step, a temperature of 40 °C for 20 min in the gluten-aging step, and gluten-washing of 2.0 min in the Glutomatic system. The HS-FWD wet-milling test with high level of repeatability was capable of discriminating wet-milling qualities of several hard, soft, and coarsely ground wheat flours.     

Phytochemical compositions, and antioxidant properties, and antiproliferative activities of wheat flour

Ten soft wheat varieties grown in Maryland were compared for their phytochemical compositions, antioxidant properties and antiproliferative activities. Free radical scavenging capacities were examined against DPPH(·), oxygen, hydroxyl and ABTS(·+) radicals. Significant radical scavenging capacities were detected in all wheat flour extracts. Total phenolic content ranged from 1.66 to 2.01 mg of GAE/g wheat flour. The wheat flours contained 172.91-297.55 μg/g insoluble bound ferulic acid, contributing 89.74-94.29% of total ferulic acid on a per weight basis. The concentrations of lutein and zeaxanthin were 0.27-0.46 and 0.08-0.13 μg/g, respectively. In addition, the wheat flours had 0.30-0.59 and 0.07-0.29 μg/g α- and δ-tocopherols, respectively. Four wheat flour extracts were further examined for their antiproliferative activities. The Jamestown wheat flour showed significant antiproliferative activity against both HT-29 and Caco-2 colon cancer cells at the initial treatment concentration of 50 mg flour equivalents/ml, while USG3555 flour showed inhibitive effect only in HT-29 cancer cells, suggesting the different and possible selective antiproliferative property of the wheat flours. These results may be used to direct the breeding effects to produce soft winter wheat varieties with improved health properties.     

非糯性大米粉糊粘度性质的研究

本文用Brabender粘度计研究了多种粳、籼米粉在不同糊浓度、pH值、蔗糖、盐存在下,糊粘度的变化性质。     

Extraction of ginsenosides from a blend of wheat flour and ginseng powder

This study explored conditions for maximum extraction of ginsenosides (G) from a blend of wheat flour (WF) and ginseng powder (GP). WF (0.9 g), GP (0.1 g), or WF–GP (0.9 g WF + 0.1 g GP) was mixed with distilled water (4.5, 0.5, or 5.0 ml, respectively) and heated at temperatures from 25 to 90 °C. Individual G (Rb1, Rc, and Rd) were fractionated and identified by RP-HPLC. Interactions between WF components and G, including interactions between the wheat starch fraction (SF) and G and between the gluten fraction (GF) and G, were observed in WF–GP heated at 90 °C. The degree of interactions between the SF and G was greater than that between the GF and G. The interactions between WF components and G decreased the amounts of G extractable from the heated WF–GP. The interactions between WF components and G could be disrupted by increasing ultrasonic extraction time to 90 min for maximum extraction.     

The effects of freeze, dry, and wet grinding processes on rice flour properties and their energy consumption

This study attempted to replace the wet grinding process of rice with a freeze grinding process. The freeze grinding process involved soaking the rice samples in liquid nitrogen before grinding in a dry grinding machine. Three different types of grinders (hammer mill, roller mill, and pin mill) were used in both the freeze and the dry grinding processes. Wet grinding resulted in significantly (P < 0.05) smaller average particle size and a lower percentage of damaged starch than the alternative methods of grinding. Freeze grinding, especially using the hammer mill significantly reduced both the average particle size and the damaged starch content. Moreover, freeze grinding produced a higher yield after sieving in comparison with dry grinding using an identical grinder. In particular, freeze grinding with the hammer mill gave a significantly higher yield after sieving than dry grinding with the hammer mill. The wet grinding process had the significantly highest specific energy consumption (13,868 kJ/kg) due to the large consumption of electrical energy by the many machines in the process. The energy consumption of freeze grinding was similar to dry grinding. Consequently, the freeze grinding process was a viable alternative to the traditional wet grinding process.     

Bread quality and dough rheology of enzyme-supplemented wheat flour

The enzymatic treatment of wheat flours is an interesting alternative for improving their functional properties. Since enzymes with different biochemical activities could induce synergistic effects on dough behaviour or product quality, the individual and combined use of a wide range of enzymes (transglutaminase, glucose oxidase, laccase, α-amylase, pentosanase and protease) applied nowadays in bread-making processes were investigated. The blend of enzymes resulted in an improvement in the rheological behaviour of doughs and the quality of the final product. The simultaneous presence of transglutaminase (TG) and glucose oxidase (GO), as well as TG and protease (PROT) led to a synergistic effect on alveograph parameters. Polysaccharide-degrading enzymes exercised a significant effect on rheology only when used in combination with other enzymes, mainly affecting consistograph parameters. Analysis of bread-making data revealed significant interactions between TG and all the other enzymes except laccase (LAC). Significant synergistic effect on bread quality was observed by the combined use of GO and LAC, GO and pentosanase (PP), amylase (AMYL) and LAC, AMYL and PROT, and PP and PROT. Bread quality parameters showed greater correlations with alveograph parameters than with consistograph properties of dough. Tenacity (P) and extensibility (L) proved to be acceptable predictors of the height/width ratio of loaves. The duration of the alveograph test enhanced the prediction of bread quality parameters. Conversely, none of the rheological properties studied showed a high correlation with the specific volume of loaves.     

Effect of extrusion cooking on protein modification in wheat flour

Common soft wheat flour was extruded at three different temperatures and two different moistures. To investigate the dependence of the wheat protein modification on processing conditions, their solubilities in sodium dodecyl sulfate (SDS) were compared with those in SDS+(2-mercaptoethanol) ME. Furthermore, free sulfhydryl groups were detected with Ellmans Reagent and SDS-PAGE was performed under reducing and non-reducing conditions. The solubility values in SDS were greatly reduced after extrusion. The solubility values in SDS+ME were not affected. We therefore concluded that intermolecular cross-linking by disulfide bonding through extrusion cooking had occurred. This result was confirmed by SDS-PAGE under reducing and non-reducing conditions. At low and medium temperatures the solubilities were lower at low moisture; however, more free sulfhydryl groups were detected under these conditions, suggesting that moisture content of the flour has an influence on the way and the nature of the protein polymerization. At the highest thermal energy input at low moisture the solubilities increased again. This was accompanied by an increase of detectable free sulfhydryl groups. This led to the conclusion that disulfide bonds were cleaved at high energy input. The solubility development in 70% ethanol was nearly the same as in SDS. This is seen as a proof that gliadins are highly involved in the protein network formed under extrusion conditions. This finding was also confirmed by the results of SDS-PAGE.     

Mechanical and barrier properties of composite films based on rice flour and cellulose fibers

Rice flour is a low-cost starchy material, produced from rice that is broken during processing. Rice flour-based films have promising application on food packaging, because of their environmental appeal and low cost. Nevertheless, their mechanical and moisture barrier properties should be improved. The aim of this study was to develop biodegradable films based on rice flour and enhance their properties by reinforcing them with cellulose fibers. In this way, rice flour films with and without fibers were prepared by casting, with glycerol or sorbitol as plasticizer. Their physicochemical, microscopic and mechanical properties were studied. SEM analysis of films revealed compact structures. Films prepared with fibers presented lower water vapor permeabilities if compared with films without fibers. Films containing sorbitol were less permeable to water and more rigid. The incorporation of fibers reinforced mechanically the flour-based films, which presented higher tensile strength, but did not influence their deformation capacity. Therefore, preparing biodegradable films from rice flour is a new alternative of using this raw material. The use of cellulose fibers as reinforcing agent is a viable alternative to improve the properties of rice flour-based films, because they are biodegradable and available at low cost.     

杂粮粉与小麦粉粘度特性比较研究

对几种杂粮粉与小麦粉的粘度特性进行了比较研究,结果显示:杂粮粉糊化温度和开始糊化的时间、热粘度及其稳定性、冷粘度及其稳定性等粘度特性都存在着明显的不同。为进一步了解小麦与杂粮淀粉的特性及应用开发提供了一定的理论依据。     

Rheological properties of wheat flour and quality characteristics of pan bread as modified by partial additions of wheat bran or whole grain wheat flour

The use of bran and whole grain flour changes dough rheology and causes difficulties in manufacturing bakery products. The aim of this study was to analyse the influence of substituting refined wheat flour (WF) by wheat bran (WB; 5%, 10%, 20%, 30% and 40%) or whole grain wheat flour (WGWF; 10%, 20%, 30%, 40% and 50%) on dough rheological properties and pan bread quality characteristics. The addition of WB and WGWF increased water absorption and resistance to extension and decreased stability, extensibility and peak viscosity. Effects with WB were more pronounced. The presence of WB or WGWF increased crumb moisture content, firmness and hardness and decreased specific volume of pan bread. It is important to set new farinographic and extensographic standards when using WB and WGWF, allowing for a correct correlation between rheology and quality characteristics of bakery products, as the same standards used for WF are not valid.