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.     

适用于柔性高压直流输电网的直流电压下垂控制策略

基于带死区的直流电压下垂控制,提出一种适用于柔性直流输电网的新型直流电压下垂控制策略,可保障直流与交流系统交换功率的平衡。提出的新型直流电压下垂控制方法首先将各换流站分为4组,之后通过对各换流站组设定不同的电压裕度和死区来设定参与协调控制的不同优先等级,最后提出改进的"功率—电压"特性曲线来确保各换流站在暂态下具备良好的动态特性。仿真测试系统的交流部分为IEEE 39节点系统,直流部分为一个5端直流电网系统,其中换流器类型为401电平模块化多电平换流器。通过对该交直流混合系统的测试,文中提出的新型直流电压下垂控制方法可以在故障发生后有效地使系统过渡至新的稳态运行点。在暂态过程中,各换流站具备良好的动态特性。     

A Microbiological Study of Sudanese Date Wines

Procedures followed in the home fermentations of three date wines were investigated. Two wines, 'sherbote', and‘nabit’prepared from date sirup, are produced by a relatively quick fermentation taking about 36-48 hr. The fermentation of the third wine;‘dakkai', prepared from whole date fruits, is a slow process taking about 96 hr. The samll amounts of spices and sorghum malt used as additives in the preparation of 'sherbote’and‘nabit', respectively, contribute to the inoculum. In‘dakkai’fermentation of the inoculum comes from the natural flora of the data fruit itself. Changes in the production of ethanol, acetic and lactic acids and pH as well as in microbial populations were followed during fermentation of each wine. The most important genera of yeast, acetic and lactic acid bacteria were identified.     

Polyconductor beam power sensor

The design is presented of a sensor circuit for the thermal detection and power measurement of incident microwave and laser beams due to accidental or targeted exposure. In this sensor, a polyconductor device acts as a microwave or optical beam absorber. The basic feature of the polyconductor is that its terminal resistance in the transition region can vary by many orders of magnitude with small changes in excitation temperature, regardless of frequency. Thus the heating effect of the incident wave changes the terminal resistance which is converted into a sensitive imbalance of a Wheatstone bridge circuit with appropriate display. This circuit is significantly improved with the aid of an ambient temperature compensation section and a feedback loop to maintain operation in the most sensitive region of the polyconductor characteristic. The sensor has proved to be adequate for a wide range of fluctuations in ambient temperature and incident power levels. Also, since the polyconductor film does not absorb any significant power beyond the transition region, it is found adequate for protecting itself and the circuit connected to it or whatever is immediately behind it, under conditions of relatively large incident beam power. This is attractive for a variety of applications in biomedical engineering as well as in the areas of electronic and laser warfare.     

Influence of Water Stress on Cold-Induced Sweetening in Leafy Vegetable, Brassica juncea L.

The occurrence of low temperature sweetening in Brussica juncen L., an apparently chilling-tolerant leafy vegetables, has been investigated in relation to the effect of water stress and postharvest age (i.e. fresh harvest vs previously stored samples). The magnitude of cold-induced sweetening in B. juncea leaves was estimated to vary from 10–145% relative to the corresponding nonchilled samples. Previously stored leaves showed greater tendency to accumulate sugars but was apparently less responsive to cold-induced sweetening than freshly harvested leaves. Water stress synergistically enhanced this low temperature sweetening response; markedly greater and/or faster accumulation of sugars occurred in leaves that were both chilled and stressed. The majority of the total sugar increase was attributable to non-reducing sugars.     

EFFECT OF VARIOUS DRYING METHODS ON TEXTURE AND COLOR OF TOMATO HALVES

Tomatoes were pretreated with osmotic solutions (NaCl and sucrose) at different concentrations and then dried using hot air (75C, 1.5 m/s), a vacuum (55C, 75 kPa) or hot-air drying followed by microwave treatment (400 W, 10 s). The effects of pretreatment and drying method on the drying kinetics were examined. A puncture test and scanning electron microscopy were used to analyze the effects of these processes on texture and microstructure. Hunter values ( L, a, b ) were used to measure color. Measurements showed that two osmotic solutions, S₃ (40% sucrose, 5% NaCl) and S₄ (40% sucrose, 10% NaCl), performed better, reducing drying times and having a positive effect on microstructure, but an adverse effect on hardness. Apart from the type of process, dehydration reduced firmness and collapsed the structure of tomato halves. The subsequent microwave treatment then caused further damage, especially on the surface of the dried samples, but enhanced their color when combined with appropriate osmotic treatment.

PRACTICAL APPLICATIONS

This study shows that the color and structural changes of tomato during drying can be reduced using appropriate procedure. This may find application in the production of dried tomato with better appearance and lower drying cost.     

Geotechnical forensic investigation of a slope failure on silty clay soil—A case study

Qila Bala Hisar is one of the noteworthy places of Peshawar, Khyber Pakhtunkhwa. The fort was constructed on a filled ground during the 18th century and it was renovated several times by the occupants ever since. Recently, due to an earthquake of magnitude 7.3, the upper part of the south-western wall of the fort collapsed. The collapse of the wall was attributed to the failure of the retained slope. This research was undertaken to characterize the slope material, study causal factors of failure and evaluate remedial strategy. The investigation involved conventional field and laboratory testing and geophysical investigation using electrical resistivity technique to evaluate the nature of stratum. Also, X-ray Diffraction and Scanning Electron Microscopy was used to study the slope material at a molecular level to evaluate the existence of swelling potential. The analysis has shown that excessive seepage of water caused by the poor maintenance of runoff and sewage drains is the causal factor triggered by the seismic event. A remedial strategy involving soil nails, micro piles and improvement of the surface drainage is recommended.