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Wheat starch was processed in a co-rotating twin-screw extruder, at moisture contents 25% and 30%, screw speeds 200 and 300 rpm, feed rate 30 kg/hr, and barrel temperature settings 100, 120, 140, and 160°C. Degree of starch gelatinization at each point along the extruder channel was determined by sampling and analyzing material inside the extruder. Kinetics of the gelatinization during extrusion was investigated. A first-order rate equation was developed to predict degree of starch gelatinization during extrusion. The rate constant was a function of both temperature and shear stress. 相似文献
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The objective of this work was to study the obtaining of cationic starch by using a pilot scale twin-screw extruder Clextral BC45 as a chemical reactor. The reagent was 3-chloro 2-hydroxypropyltrimethyl ammonium chloride (CHPTMA) and catalyst was sodium hydroxide (NaOH). In a first set of experiments extruded starch gave higher chemical efficiencies than native starch (+15%) both being fed at the same location of the barrel. Influence of extrusion conditions on reaction kinetics was studied starting from extruded starch in order to optimize the reaction without interfering with starch melting phenomenon. In a second set of experiments, a special screw design was implemented in order to obtain a homogeneous starch molten phase in a first stage, and to achieve starch modification in a second stage. Changes of reacting conditions were performed through the modification of reagent quantities and molar ratios related to starch and NaOH, location of reagent injection, temperature of reaction and Specific Mechanical Energy input. Samples were evaluated through their degree of substitution (final DS < 0,09); their homogeneity and rheological behavior were studied by ion exchange chromatography and Brabender viscoamylograph. resp., Reaction efficiency was computed to optimize the process, leading to values up to 82%. Extruded samples were then compared to commercial cationic starches. 相似文献
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ABSTRACT: Using the results from twin-screw extrusion of corn meal, both energy consumption and extruder efficiency were found to be significantly correlated with screw speed and specific feeding load (SFL). An increase in the SFL decreased the total specific mechanical energy, but increased the extruder efficiency. SFL influenced the extruder efficiency more than the screw speed. Increasing the screw speed from 300 to 450 rpm at a constant SFL level increased the extruder efficiency by 6 to 11%, whereas an increase of SFL from 0.0026 to 0.0038 kg rev 1 raised the extruder efficiency by 30%. Of the mechanical energy consumed per unit mass of extrudate, over 98% were used for shearing or viscous dissipation and less than 1.5% were for pumping during twin-screw extrusion of corn meal. 相似文献
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The washed minced meat of flying fish was extruded at low temperatures with NaCl in a twin-screw extruder while varing screw rotation, feeding rate, feeding of NaCl, and barrel temperature. Extrusion at a higher screw rotation and moderate feeding rate with the residence time of about 1 min, using NaCl in solution and with cooling by ice-water, gave the most adhesive meat sol. Heat-induced gel from this meat sol had a similar textural parameters measured by an instrument to the gel prepared with a conventional stone grinder, however, the toughness score in sensory test of the gel prepared by extrudate was a little smaller than the gel by a conventional method. 相似文献
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为了获得直接挤压制备米粉(线)的最适工艺参数,采用响应面(RSM)方法设计试验方案,对挤压机挤压制作米粉的工艺参数进行优化分析。研究原料含水量、机筒温度、螺杆转速对米粉糊化度的影响。结果表明:3个因素对糊化度影响大小依次为机筒Ⅲ区温度>螺杆转速>原料含水量。通过响应面分析得出挤压米粉最佳工艺:原料含水量35.1%,Ⅲ区温度102℃,螺杆转速117 r/min。在此条件下,米粉糊化度为92.1。与3种市售产品对比,自制米粉在硬度、糊化度、咀嚼性和感官品质方面达到了市售产品平均水平。 相似文献
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Infrared (IR), extended melt and flush thermocouple probes were used to measure bulk temperatures of extrudates. Good agreement was obtained between IR and extended probes. However, substantial differences were observed between IR and flush mounted probes and between extended and flush mounted probes. A response surface methodology was used to study effects of moisture screw speed, and barrel temperature on measured temperature differences between IR and flush probes. The standard flush probe may not accurately measure bulk temperature of the extrudate. The heat flux from the surfaces (top, bottom, and side) of a twin-screw extruder barrel was also measured. Total heat loss from the surface varied between 2–19% of the total heat input. 相似文献
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物料在双螺杆挤压机中停留时间分布的研究 总被引:2,自引:1,他引:2
阐述了物料在双螺杆挤压机中停留时间分布的理论,从设计模型和检测方法方面描述了物料的停留时间分布,并指出了影响停留时间分布的因素,为更好地选择和控制挤压机系统和操作提供了依据。 相似文献
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双螺杆挤压生产虾饲料的工艺参数研究 总被引:2,自引:0,他引:2
采用双螺杆挤压机,以糊化度、耐水性、膨化度和密度为主要指标,研究物料水分质量分数、喂料速度、螺杆转速、揉和区和熟化区的机筒温度对最终产品质量特性的影响.研究表明:随物料水分含量增加,产品糊化度增大,耐水性增强,膨化度变小,密度增大;随喂料速度和螺杆转速增加,产品糊化度和耐水性增强,膨化度变大,密度减小;随揉和区和熟化区的机筒温度升高,糊化度增大,耐水性增强,熟化区机筒温度对产品密度影响较大,温度降低则密度增大.挤压虾饲料的适宜加工工艺参数为:物料水分质量分数为26%~32%,喂料速度为30 r/min,螺杆转速为70 r/min,揉和区和熟化区机筒温度分别为130和50℃. 相似文献
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The effect of extrusion cooking in a single screw extruder on the molecular weight distribution of wheat starch was correlated to the starch melt rheology. A simple first-order model has been developed which defines the extent of mechanical degradation of the amylopectin component as a function of nominal shear stress and residence time in the extruder. A limited set of experimental observations were used to test the model. Iso-shear stress curves were calculated for the experimental range of conditions. The curves can be used, in conjunction with estimates of the residence time, to calculate equivalent processing conditions, and to predict the extent of amylopectin degradation. The model may allow the use of small extruders to determine fundamental process parameters for full scale extrusion. 相似文献
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Effects of Salt, Sugar and Screw Speed on Processing and Product Variables of Corn Meal Extruded with a Twin-Screw Extruder 总被引:1,自引:0,他引:1
The effects of screw speed and additives (sugar and salt) on processing and product variables of corn meal extruded with a twin-screw extruder were studied. Higher salt (0–3%) and sugar concentrations (0–4%) in the feed decreased the die pressure, % torque and specific energy. But at 6 and 8%, sugar increased the three processing parameters. Higher screw speed (250 vs 200 rpm) decreased die pressure and % torque, but increased specific energy. The addition of salt and sugar enhanced extrudate radial and axial expansions, but reduced product bulk density and breaking strength. An increase in screw speed decreased radial expansion and bulk density, but increased axial expansion and breaking strength. 相似文献
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本文主要研究双螺杆法分离胡麻韧皮部和木质部纤维所得纤维的制浆性能,以及加入NaOH等药品对其制浆性能的促进作用。结果发现,双螺杆法可使胡麻韧皮部和木质部纤维得以很好的分离(总得率可达40.4%),加入药品后韧皮部纤维100g/m2定量纸张的抗张和撕裂指数以及耐折度可达56.36 N.m/g、42.84 mN.m2/g和168次,比不加药品是高出了25%、30%和60%左右。与此同时,木质部纤维在经过磨浆处理后也可成浆,其50g/m2定量纸张的抗张和撕裂指数以及耐折度可达42.47N.m/g、5.30 mN.m2/g和10次,与不加药品相比提高了约100%、70%和200%。因此,综合可知,双螺杆法可将胡麻韧皮部和木质部纤维得以较好的分离,加入一定量NaOH等化学药品可提高其制浆性能,最终可针对两种纤维的性质,将二者进行合理利用,提高胡麻作为制浆造纸原料的利用效率。 相似文献
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双螺杆挤压机的系统模型 总被引:2,自引:0,他引:2
本文指出了双螺杆挤压机系统的影响因素,从挤压系统的目标函数出发描绘了各因素与目标函数的相互影响过程,最后建立了一种双螺杆挤压机的系统模型 相似文献
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Twin-screw extrusion was evaluated as a pretreatment for the enzymatic hydrolysis of cassava starch to glucose. Extrusion temperature and pH affected the key parameters associated with the enzymatic hydrolysis of starch such as the water solubility index, the water absorption index, the apparent viscosity, and the susceptibility of the extruded starch to glucoamylase. The glucose concentration of extruded and enzyme-hydrolyzed cassava starch was approximately 5% greater than that of acid-liquefied and enzyme-hydrolyzed cassava starch. 相似文献
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林纸一体化企业总体构架和运作模式的基本思路 总被引:3,自引:0,他引:3
在简要分析建立林纸一体化企业的必要性的基础上,列举了我国建立林纸一体化企业在纸品市场、造林营林技术、造纸技术装备和资金供应四个方面已具备的客观条件。进而探讨了我国林纸一体化企业的基本框架,指出按照现代企业制度新建大型林纸一体化股份有限公司,和以现有的林业企业、纸业企业为基础,组建大型林纸一体化企业集团,是实现林纸一体化的基本模式。并进一步探讨了这两类企业的运作方式。 相似文献
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Residence time distributions for wheat starch in a single screw extruder were measured for different operating conditions using a manganese dioxide tracer. Two flow models which differed in the definition of dead space were used to represent the flow pattern in the extruder. The parameters for each model were fitted using the experimental residence time distributions. Screw speed and the moisture level of the feed showed the strongest effects on the average residence time. A small fraction of the flow, 5–20%, was held up in the dead space region. The remainder passed directly through the active region with a residence time distribution close to plug flow. An apparent power law index for the starch melt was calculated and over the experimental range of extrusion conditions it varied from 0.2 to 1.0. 相似文献