Impacts of Cellulose Fiber Particle Size and Starch Type on Expansion During Extrusion Processing

Objective of this study was to understand the impacts of cellulose fiber with different particle size distributions, and starches with different molecular weights, on the expansion of direct expanded products. Fiber with 3 different particle size distributions (<125, 150 to 250, 300 to 425 μm) and 4 types of starches representing different amylose contents (0%, 23%, 50%, and 70%) were investigated. Feed moisture content (18 ± 0.5 % w.b) and extruder temperature (140 °C) were kept constant and only the extruder screw speed was varied (100, 175, and 250 rpm) to achieve different specific mechanical energy inputs. Fiber particle size and starch type significantly influenced the various product parameters. In general, the smaller fiber particle size resulted in extrudate with higher expansion ratio. Starch with an amylose: amylopectin ratio of 23:77 resulted in highest expansion compared to the other starches, when no fiber was added. Interestingly, starch with 50:50, amylose: amylopectin ratio in combination with smaller fiber particles resulted in product with significantly greater expansion than the control starch extrudates. Aggregation of fiber and shrinkage of surface was observed in the Scanning Electron Microscope images at 10% fiber level. The results suggest the presence of active interactions between the cellulose fiber particles and corn starch molecules during the expansion process. A better understanding of these interactions can help in the development of high fiber extruded products with better expansion.     

Nucleation and Expansion During Extrusion and Microwave Heating of Cereal Foods

Expansion of biopolymer matrices is the basis for the production of a wide variety of cereal foods. A limited number of manufacturing processes provide practical solutions for the development of an impressive variety of expanded products, just by changing process variables. It is therefore essential that the mechanisms involved in expansion are well known and controlled. This paper summarizes the knowledge of nucleation and expansion in extruded and microwaved products available to date. The effect of processing conditions and properties of the biopolymeric matrix on nucleation and expansion are discussed. Moisture content enables the glassy polymeric matrix to turn into rubbery state at process temperatures, which allows superheated steam bubbles to form at nuclei and then expand, expansion being governed by the biaxial extensional viscosity of the matrix. Nucleation and expansion theories are presented along with quantitative data that support them.     

Nozzle Dimension Effects on the Expansion of Extrusion Cooked Corn Starch

Normal corn starch was extruded through nozzles with different length to diameter ratios (L/D). The expansion ratio of the extrusion-cooked starch increased from 4.5 to 13.0 as the extruder nozzle L/D increased from 2.5 to 3.4 and then decreased gradually to 8.5 as the nozzle L/D was increased to 10.3. The back-pressure in the extruder barrel was directly proportional to the nozzle LKI ratios, with the optimum expansion at approximately 7 MPa.     

双螺杆挤压温度对玉米淀粉结构和理化性质的影响

淀粉在挤压机内的熔融行为变化影响着挤出物的物理性质,探究淀粉挤压过程中熔融行为对于生产理想的热塑性淀粉基材料具有重要意义。本文探究不同挤压温度（60、70、80、90和100 ℃）对玉米淀粉结构和理化性质的影响。结果表明,在高温和机械剪切作用下,淀粉颗粒发生破碎,颗粒尺寸减小。淀粉分子内氢键被破坏,使淀粉更易与水分子结合,从而提高了热塑性淀粉（TPS）的水合特性。随着温度升高,直链淀粉含量增加,相对结晶度（RC）和双螺旋有序度（DO）减小,表明玉米淀粉在受热过程中长程和短程有序结构被破坏。挤压机的高温处理降低了TPS的焓值,破坏了淀粉糊形成凝胶网络的能力,样品存在弱凝胶行为,但刚性和弹性减弱。综上所述,双螺杆挤压温度使淀粉颗粒结构、晶体结构、水合特性和流变特性发生了不同程度的变化,为挤压优质热塑性淀粉材料提供新思路。     

Shear Induced Starch Conversion During Extrusion

Using a capillary rheometer and a singlerscrew extruder, waxy corn starch was extruded at a relatively low temperature range. Notable conversions induced by shear energy were obtained in very short residence times (from several sec to 1 min). Conversions up to > 70% were also achieved. Kinetic studies showed that conversion caused by shear energy was more efficient than that by thermal energy. The shear rate constant, k, was an exponential function of shear stress and a linear function of shear rate. The minimum shear stress required to cause starch conversion was from 10⁴ to 10⁶ N/m² for 100°C to 21°C. In such “shear” experiments, the maximum temperature rise due to viscous thermal dissipation, measured experimentally and calculated theoretically, was too low to cause any significant thermal cooking of starch. The shear converted starch extrudates were unpuffed and had shapes of traditional pasta.     

Screw Configuration Effects on Macroscopic Characteristics of Extradates Produced by Twin-screw Extrusion of Rice Flour

The effects of 29 screw configurations on rice flour extrudates were investigated. The moisture content, screw speed and feed flow rate during all extrusion experiments were 15%, 400 rpm, and 12kg/h, respectively. Temperature profile in the 8 barrel sections from feed to die end were set at 0, 30, 30, 30, 70, 100, 150, and 150°C. Incorporation of kneading block (KB) and reverse screw element (RSE) in screw profiles significantly influenced apparent density, product expansion (radial, axial and overall), and breaking strength. Apparent density and overall expansion were functions of die temperature. KB was the best element for maximizing radial expansion. Product hardness (breaking strength) decreased with increasing radial expansion.     

挤压法制备的硬脂酸玉米淀粉酯的性质研究

以玉米淀粉为原料,硬脂酸为酯化剂,用双螺杆挤压机作反应器制备了硬脂酸玉米淀粉酯.对硬脂酸玉米淀粉酯的黏度、稳定性、溶解度、糊化度、乳化特性和消化性等性质进行了测定和分析.     

双螺杆挤压制备酯化玉米淀粉的实验研究

以玉米淀粉为原料,醋酸乙烯酯为酯化剂,用双螺杆挤压机制备酯化淀粉。研究了各反应因素对产品取代度(DS)的影响,并以DS为指标,通过正交实验确定了其最佳工艺条件:挤压温度90℃,螺杆转速80r/min,反应体系pH值9.5,酯化剂浓度2%,物料含水率30%。对产品的糊化性和凝沉性等理化性质做了测定和分析。     

Changes in Starch and Protein on Extrusion of Corn Starch and Sunflower Protein Blends

We investigated the use of electron spin resonance spectroscopy (ESR) and the spin labelled fatty acid, 16 doxylstearic acid (16-DSA) in the study of starch and protein modification during extrusion processing of corn starch (CS), corn meal (CM), and their blends with sunflower protein isolate (SPI). Spectra due to binding of the spin probe to starch and protein were identified. Changes in spectra after extrusion of all materials indicated that: (1) ~90% of the starch was modified (gelatinized); (2) The globular protein structure was disrupted. These changes demonstrate that spin probes and ESR spectroscopy may be used to study starch and protein modification during extrusion and other food processes.     

玉米产品挤压膨化特性的影响因素

以优质的玉米为原料,采用挤压膨化技术,研制出玉米膨化产品。通过正交试验确定了挤压温度、物料水分含量、螺杆转速对产品膨化物糊化度的影响,并找出了最佳工艺参数值:挤压温度160℃,物料水分含量20%,螺杆转速300r/min。     

双螺杆挤压对菠萝蜜种子淀粉消化特性及血糖指数的影响

为探究双螺杆挤压对菠萝蜜种子淀粉(JFSS)的消化特性及血糖指数的影响,采用体外消化试验,考察了JFSS经挤压处理前后的消化性与消化动力学变化,并通过水解指数(HI)、血糖指数(GI),预测了菠萝蜜种子淀粉的餐后血糖水平(PPBS)。结果表明,双螺杆挤压增加了快速消化淀粉(RDS)与慢消化淀粉(SDS)含量,提高了平衡浓度(C_∞)、酶解速率(k)、水解指数(HI)、血糖指数(GI)和淀粉消化率,显著降低了抗性淀粉含量(RS)(P<0.05)。在低水分含量下,增加螺杆转速与机筒温度,RDS含量由47.85%增加到58.91%,且k、C_∞、HI、GI值也均呈现增加趋势,而SDS含量、RS含量呈降低趋势。螺杆挤压使菠萝蜜种子淀粉由致密结构转变为疏松多孔的多面体结构。     

Starch Conversion During Extrusion as Affected by Added Gelatin

Waxy maize starch was modified by twin-screw extrusion cooking in the presence and absence of gelatin. X-ray diffraction, microscopy, rheology, and differential scanning calorimetry studies showed that, at constant specific mechanical energy and extruder heater temperatures, the degree of starch conversion decreased with increasing levels of gelatin. It was hypothesized that during extrusion cooking, the gelatin acts as a lubricant, protecting the starch from being converted since more mechanical energy would be dissipated in the gelatin phase than the starch phase.     

淀粉老化对微波膨化影响的研究

采用Ｘ－ 衍射方法确定了淀粉物料的老化程度,并研究了淀粉的老化对其微波膨化的影响,探讨了淀粉老化对微波膨化影响的机理。     

螺杆挤压过程食品流动能力计算与综合修正

螺杆挤压推料是食品加工过程中完成食品的输送、挤压与混合的常用工序,确定螺杆挤压过程食品流动能力,是为研究食品加工工艺及设备提供必要的条件。本文针对具有幂律非牛顿流体特性的一类食品,对前人的螺杆挤压流动模型及公式进行了简化与扩展,并提出了一种模型修正法--综合系数修正法。     

湿热处理玉米淀粉的溶胀和水解性质初探

对三种不同链淀粉含量的玉米淀粉(高链玉米淀粉、普通玉米淀粉和蜡质玉米淀粉)经湿热处理前后的溶胀及酸、酶水解性质进行研究,探索湿热处理对淀粉微观性质的影响。研究结果表明:湿热处理后淀粉的膨胀度和溶解度较原淀粉减小;湿热处理淀粉在酸、酶作用初期水解率比原淀粉大,后期由于经湿热处理后淀粉链之间的重新结合,形成了新的双螺旋结构,结合更为紧密,酸、酶难于作用,水解率较原淀粉降低。     

Impacts of Scarification and Degermination on the Expansion Characteristics of Select Quinoa Varieties during Extrusion Processing

Extrusion of 2 quinoa varieties, Cherry Vanilla and Black (scarified and unscarified) and a mixed quinoa variety, Bolivian Royal (scarified and degermed) were studied for their extrusion characteristics. A corotating twin‐screw extruder with a 3 mm round die was used. Feed moisture contents of 15%, 20%, and 25% (wet basis) were studied. The extruder barrel temperature was kept constant at 140 °C and screw speeds were varied from 100, 150, and 200 revolutions per minutes. Process responses (specific mechanical energy, back pressure, and torque) and product responses (expansion ratio, unit density, and water absorption index/water solubility index) were evaluated. The degermed Bolivian Royal showed the highest expansion in comparison to all other varieties, attributed to its significantly low levels of fat, fiber, and protein. The scarified Cherry Vanilla resulted in the lowest expansion ratio. This was attributed to the increase in the protein content from the removal of the outer layer. The results indicate that all the varieties performed differently in the extrusion process due to their modification processes as well as the individual variety characteristics.     

Single-Screw Extrusion of Defatted Soy Flour, Corn Starch and Raw Beef Blends

Effects of feed moisture, fat and corn starch levels and process temperature on physical properties of extrudates of defatted soy flour-amylose corn starch-raw beef blends were investigated using response surface methodology. Contour plots showed a convex curve of expansion ratio (ER) with moisture, concave curves of bulk density (BD) and shear-force (SF) with moisture, and concave cmves of SF with each of the four extrusion variables. Fat decreased ER and increased BD, whereas corn starch increased ER. Products with high ER and low BD and SF tended to have prominent air cells, continuous protein matrices, and smooth cell wall surfaces in scanning electron micrographs. The optimum extrusion conditions for minimal SF values, with 20% non-dehydrated beef muscle and varied amounts of defatted soy flour, were: 29.1% feed moisture; 2.96% feed fat; 22% feed corn starch; and 162°C process temperature.     

玉米膨化食品加工参数研究

以玉米糁为材料，采用DSE-25型双螺杆挤压膨化实验室工作站为加工设备，分析了加工温度和物料含水量对扭矩、压力、膨化率和产品含水量的影响。结果表明，在试验设计的加工温度和物料含水量范围内，加工温度和物料含水量对螺杆扭矩、第4区压力、第5区压力、产品膨化率和含水量都有极显著影响。加工温度对第4区压力影响较大；物料含水量对扭矩、第5区压力、产品膨化率和含水量影响较大。随着加工温度上升，物料含水量增加，扭矩、压力、产品膨化率降低；随着加工温度升高，物料含水量下降，产品含水量降低。     

双螺杆挤压对大豆蛋白体外消化率的影响

采用双螺杆挤压技术,研究了挤压工艺参数对大豆蛋白体外消化率的影响,并采用二次通用旋转组合设计,建立了大豆蛋白体外消化率与物料含水量、挤压温度、喂料速度、螺杆转速的二次回归方程,并利用该方程探讨了各因子对消化率的影响.结果表明,各因子对大豆蛋白体外消化率的影响顺序为:挤压温度>物料含水量>螺杆转速>喂料速度,物料含水量与挤压温度交互作用显著.利用统计优选法寻优,确定了大豆蛋白消化率的最佳挤压工艺条件:物料含水量35%,挤压温度155℃,喂料速度0.4 kg·min-1,螺杆转速150r·min-1,大豆蛋白体外消化率最高值为95.83%.     

螺杆挤出热塑性淀粉黏度特性研究

本研究以普通玉米淀粉为主要原料,以甘油为增塑剂,采用双螺杆挤出法制备热塑性淀粉,考察了甘油/淀粉质量比、挤压机三区温度和螺杆转速3个因素对热塑性淀粉的挤出扭矩和糊化性质的影响,从热塑性淀粉熔体和热塑性淀粉糊两个方面分析了热塑性淀粉的黏度特性.