Model for Gelatinization of Wheat Starch in a Twin-Screw Extruder

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.     

Use of a Twin-Screw Extruder as a Chemical Reactor for Starch Cationization

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.     

Continuous Production of Fish Meat Sol using a Twin-Screw Extruder

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.     

Accurate Measurement of Extrudate Temperature and Heat Loss On A Twin-Screw Extruder

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.     

国外双螺杆挤压膨化机的研究现状

为适应纤维食品加工技术的需要,本文从挤出理论,物料流型及混合效果,停留时间分布等方面介绍了国外８０年代以来双螺杆挤压膨化机的研究动向。     

双螺杆挤压鸡肉混合物工艺参数的优化

以大豆、大米、鸡肉、全脂乳粉为原料,按一定比例混合,采用Box-Behnken中心组合试验研究双螺杆挤压工艺参数。综合考察物料含水率、喂料速度、螺杆转速、温度对糊化度的影响,在此基础上对变量进行响应面分析,得出最佳挤压参数是:物料含水率23.32%,五区温度105℃,螺杆转速160r/min,喂料速度30r/min。     

双螺杆挤压生产虾饲料的工艺参数研究

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℃.     

A Model for Mechanical Degradation of Wheat Starch in a Single-Screw Extruder

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.     

Effects of Salt, Sugar and Screw Speed on Processing and Product Variables of Corn Meal Extruded with a Twin-Screw Extruder

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.     

双螺杆挤压机的系统模型

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     

胡麻双螺杆法皮杆分离后的制浆性能研究

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。     

双螺杆磨浆机的研究与应用

从双螺杆磨浆机的产生和发展、磨浆工作原理及其应用、双螺杆磨浆机的理论与实验研究等方面综述了国内外关于双螺杆磨浆机的研究和应用情况,并且对今后双螺杆磨浆机的研究进行了展望.     

Twin-Screw Extrusion as a Continuous Pretreatment Process for the Enzymatic Hydrolysis of Cassava

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.     

林纸一体化企业总体构架和运作模式的基本思路

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。     

Residence Time Distributions for Wheat Starch in a Single Screw Extruder

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.     

同向双螺标食品挤压机中传热模型的研究

建立双螺杆挤压机各组成部分的模型,分析物料在各组成部分的能量、温度和时间分布情况,并结合实验数据和理论依据进行比较分析。     

双螺杆挤压亚麻籽粕脱除生氰糖苷的研究

利用BrabenderDSE-25双螺杆挤压机对亚麻籽粕进行了挤压脱除生氰糖苷的试验,考察了加工条件(水分含量、加工温度、螺杆转速、喂料速度)对系统参数(扭矩、4区压力、5区压力)和脱毒效果的影响。结果表明,使用双螺杆挤压处理能达到使生氰糖苷降解脱毒的目的,合理的脱毒工艺参数:水分含量30%,加工温度80-120-130-140-150℃,螺杆转速120r/min,喂料速度18r/min,总氰化物脱除率为96.59%,生氰糖苷含量由257.85mg/kg降低至8.79mg/kg。     

Twin-Screw Extrusion Modification of a Corn Fiber and Corn Starch Extruded Blend

Surface response modeling was used to characterize the effect of extrusion processing on the functional properties of corn fiber/corn starch formulations. Process parameters evaluated included screw speed (200-500 rpm), temperature (90-150°C) and pH (3-11). Generally, the water holding capacity of starch increased with increasing extrusion temperature while the water holding capacity of the fiber decreased with increasing extrusion temperature. The foam stability decreased, while the residual moisture increased, with an increase in fiber concentration. X-ray diffraction profiles indicated that extrusion did not affect fiber crystallinity. No significant changes in the ratio of soluble to insoluble fiber were found as a result of extrusion.     

挤压机压力控制系统的构成与调试

根据在实践中总结的经验 ,介绍了在纺粘法非织造布生产线中实现螺杆挤压机压力控制系统的作用、构成和调试方法 ,对熔体压力、控制点的选择以及系统组成和调试作了较详细的论述     

On-line Measurement of Residence Time Distribution in a Food Extruder

A technique was based on electrical conductivity of material in a die, and used a series circuit consisting of a 5 mm dia die, a 10 ohm resistor, and a 15V dc power supply. Material conductivity was altered with addition of an electrolyte tracer at the feed inlet. Change in current flow was measured as a proportional voltage response across the resistor. Using a twin-screw extruder, with L/D 32:1, the RTD of rice flour at 15% moisture was determined using sodium nitrate as tracer. Under steady state, the voltage across the resistor was measured. The on-line results correlated well with the established erythrosine dye method. The effects of screw configuration, feed flow rate, and screw speed were precisely determined by the on-line method.