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1.
We have modeled a rice extrusion process focusing specifically on the starch gelatinization and water solubility index (WSI) as a function of extrusion system and process parameters. Using a twin‐screw extruder, we examined in detail the effect of screw speed (350–580 rpm), barrel temperature, different screw configurations, and moisture content of rice flour on both extrusion system parameters (product temperature, specific mechanical energy [SME], and residence time distribution [RTD]) and extrudate characteristics (expansion, density, WSI, and water absorption index [WAI]). Changes in WSI were monitored to reveal a relationship between the reaction kinetics during extrusion and WSI. Reaction kinetics models were developed to predict WSI during extrusion. WSI followed a pseudo first‐order reaction kinetics model. It became apparent that the rate constant is a function of both temperature and SME. We have developed an adaptation of the kinetic model based on the Arrhenius equation that shows better correlations with SME and distinguishes data from different screw configurations. This adaptation of the model improved predictability of WSI, thereby linking the extrusion conditions with the extruded product properties. 相似文献
2.
Wheat flour with 0.3% (w/w) thiamin was extruded on a twin‐screw laboratory‐scale extruder (19‐mm barrel) at lower temperatures and expanded using carbon dioxide (CO2) gas at 150 psi. Extrusion conditions were die temperature of 80°C and screw speed range of 300–400 rpm. Control samples were extruded at a die temperature of 150°C and screw speed range of 200–300 rpm. Dough moisture content was 22% in control samples and 22 and 25% in CO2 samples. Expansion ratio, bulk density, WAI, and %WSI were compared between control and treatment. CO2 injection did not significantly increase expansion ratio. Bulk densities in the CO2 extruded samples decreased when feed moisture decreased from 25 to 22%. The products using CO2 had lower WAI values than products puffed without CO2 at higher temperatures. The mean residence time was longer in CO2 screw configurations than in conventional screw configurations. Thiamin losses were 10–16% in the control samples. With CO2, thiamin losses were 3–11% at 22% feed moisture, compared with losses of 24–34% at 25% moisture. Unlike typical high‐temperature extrusion, thiamin loss in the low‐temperature samples decreased with increasing screw speed. Results indicate that thiamin loss at lower extrusion temperatures with CO2 injection is highly dependent on moisture content. 相似文献
3.
The residence time distribution and barrel fill of pet food in a twinscrew extruder was determined under conditions of a constant ratio of feed rate to screw speed. Specific feeding load was held constant at 0.16 kg/hr/ rpm while feed rate ranges were 24–56 kg/hr and screw speed ranges were 150–350 rpm. The residence time rapidly decreased as feed rate and screw speed increased. The spread of the residence time distribution (RTD) was smaller at higher feed rates and screw speed, however analysis of the normalized RTD indicated greater mixing. The barrel fill was constant at ≈50% throughout the range of experimental conditions. 相似文献
4.
The effects of moisture, screw speed, and barrel temperature on pasting behavior of refabricated rice grains were investigated in a corotating twin‐screw extruder with response surface methodology. The rice flour obtained from broken rice (≤1/8 of actual kernel size) of PR‐116 variety was used in the study. The screw speed was set at five levels between 49 and 150 rpm, barrel temperature between 59 and 110°C, and feed moisture between 31 and 45%. All pasting properties of refabricated grains evaluated—peak viscosity, hold viscosity, breakdown viscosity, final viscosity, and setback viscosity—were significantly (P < 0.01) affected by the three process variables. Barrel temperature was the most significant variable, with quadratic effect on all viscosity parameters. Response surface regression models were established to correlate the viscosity profile of refabricated rice grains to the process variables. The optimum moisture content, screw speed, and barrel temperature estimated by a response surface of desirability function for the production of refabricated rice were 36%, 130 rpm, and 89.5°C, respectively. Scanning electron microscopy also revealed that intermediate moisture and temperature along with high screw speed during extrusion could create a more realistic appearance of refabricated rice with less rupture of starch granules. 相似文献
5.
A series of cross‐linked (0, 0.014, 0.018, 0.024, and 0.028% POCl3, dry starch basis) hydroxypropylated (8%) corn starches were extruded using a Leistritz micro‐18 co‐rotating extruder. Process variables included moisture, barrel temperature, and screw design. Differential scanning calorimetry and X‐ray diffraction studies showed the level of starch crystallinity decreased with increasing severity of extrusion conditions. Pasting properties of the extruded starches were examined using a Rapid Visco Analyser. Pasting profiles of starches extruded at different conditions displayed different hot paste viscosity and final viscosity. Increasing starch moisture content during extrusion and level of cross‐linking increased starch viscosity (P < 0.0001), whereas increasing extrusion temperature and shear decreased starch viscosity (P < 0.0001). Interactions were found between level of cross‐linking and screw design and between extrusion temperature and starch moisture content (P < 0.0001). 相似文献
6.
挤压加工参数对重组米生产过程及产品膨胀度的影响 总被引：3，自引：1，他引：2
为了考察重组米生产过程中挤压加工变量对几种系统参数与产品膨胀度的影响,试验以杂交籼米（9?718品种）为原料,利用响应面模型,以螺杆转速、进料速度、进料含水率以及末端机筒温度为输入变量,以挤压系统参数（物料温度、模头压强、扭矩、比机械能和产品含水率）和重组米膨胀度为响应变量,探索在重组米生产过程中加工变量与系统参数及产品膨胀度的关系。结果表明,压强、比机械能和产品膨胀度都受到4个挤压变量的显著影响,但是物料温度受进料速度影响不显著,马达扭矩受末端机筒温度影响不显著,产品含水率仅受进料含水率的显著影响。比机械能与螺杆转速正相关,与进料速度、进料含水率和末端机筒温度负相关。所得二次回归模型均拟合良好,建立的挤压数学模型可应用于重组米生产,为重组米工业化生产的过程预测和产品性质预测提供参考。 相似文献
7.
An in‐line slit‐die viscometer (SDV) was used to measure the viscosity of a melt extrudate independently of the extruder operating conditions. The melt produced by extrusion of the corn grits followed a power law rheological model. The viscosity of the melt and extrusion parameters such as specific mechanical energy (SME), torque, and die pressure decreased with increasing moisture content. The degree of starch gelatinization increased when barrel temperature increased from 90 to 130°C. At temperatures higher than 130°C, most of the starch had gelatinized. The increase in barrel temperature, however, resulted in small changes in the apparent viscosity of the melt, until a maximum of ≈130°C. At a constant feed rate, SME increased and torque decreased when screw speed increased due to the shear thinning behavior of the melt. At a constant screw speed, the torque increased and SME decreased with increasing feed rate. This was due to a decrease in apparent viscosity of the melt at higher feed rates. SME is not an independent extrusion variable and should be used with caution either when predicting the effect of thermomechanical treatment of the product or as the key and only variable for controlling the food extrusion process. 相似文献
8.
Efficiency of oil extraction from corn germ was improved by the extrusion pretreatment, and residual oil was taken as the index of this oil extraction process. An orthogonal rotation combination test design of five levels and four factors, consisting of the moisture of material, screw speed, barrel temperature, and die nozzle diameter, was employed to optimize the model and reaction condition. The optimum parameters of extrusion were as follows: moisture of material, W = 12%; extrusion temperature, T = 105°C; screw speed, n = 185 rpm; die nozzle diameter, Φ = 9 mm × 3. Under these optimum conditions, residual oil of this process was 0.61–0.66%, which was lower than residual oil by pressing alone (residual oil of 5–6%) or by a combination of prepressing and hexane extraction (residual oil of nearly 2%). The corn oil obtained by the optimum extrusion parameters was analyzed, and iodine value, acid value, peroxide value, and saponification value were 1,250 g/kg, 400 mg/kg, 5.1 mmol/kg, and 189%, respectively. 相似文献
9.
A model was developed for the influence of particle size on the extrusion of a fish feed and the physical characteristics of the extrudates evaluated. The study was conducted using factorial experiments in a fractional replication design for four variables with three levels, and one‐third of the replicates (34 factorial in 27 units) were examined in a laboratory extruder. The torque‐screw speed measurement was used to develop a viscosity model equation that considered different shear rates, product temperature, initial moisture content, and particle size. When particle size decreased, the apparent viscosity became smaller. The barrel pressure was important in producing extrudate with a uniform volume over the range of processing conditions tested because it had a strong correlation with the volumetric expansion. The material with lower moisture and larger particles caused the specific mechanical energy to increase. The viscosity model developed in this study can be applied to the development of large‐scale extrusion models that determine the effect of particle size on the feed material extrudates. 相似文献
10.
Brown rice flour was mixed with a Chinese medical plant (Euryale ferox Salisb.) and processed to make ready‐to‐eat breakfast cereals using twin‐screw extrusion. Levels of 15 and 20% feed moisture in flour, and 200 and 250 rpm screw speed were set, and the physicochemical properties and content of α‐, β‐, γ‐, and δ‐tocopherols were determined. The data showed that 15% feed moisture gave a low bulk density and water absorption index but a high expansion ratio and water solubility index. High screw speed (250 rpm) produced a result similar to that of 15% feed moisture. A sample with 85% brown rice flour with 15% E. ferox Salisb. retained the highest content of α‐, β‐, γ‐, and δ‐tocopherols (125, 6, 78, and 9 μg/g), respectively. The optimum extrusion conditions determined were 15% E. ferox Salisb. mixed with brown rice at 15% feed moisture and at 250 rpm screw speed. 相似文献
11.
F. Martínez-Bustos Y. K. Chang A. C. Bannwart M. E. Rodríguez P. A. Guedes E. R. Gaiotti 《Cereal Chemistry》1998,75(6):796-801
The effects of added calcium hydroxide (0.0, 0.15, 0.25, and 0.35%) and processing conditions, feed moisture content (mc) (16, 18, and 20%) and barrel temperature (130 and 150°C) on characteristics of corn meal extrudates were studied. Extruder screw speed was maintained at 130 rpm. Corn meal was extruded with a single-screw extruder (Brabender model GNF 1014/2) with a screw compression ratio of 3:1. The highest values (P < 0.05) for radial expansion and the lowest values for density and breaking force of extrudates were found for the treatment with 0.00% calcium hydroxide extruded at 16% feed mc and 130°C barrel temperature. This treatment was statistically different from the other treatments. Best values for radial expansion of samples extruded with added calcium hydroxide were for the samples with 0.15% calcium hydroxide at 18% feed mc and 130°C barrel temperature, followed by the sample with 0.35% calcium hydroxide at 16% feed mc and 130°C barrel temperature. Water absorption index and water solubility index were affected by calcium hydroxide and extrusion conditions evaluated. Extrudates had large numbers of flattened and sheared granules. Increases in calcium hydroxide increased extrudate yellowness. The combined action of calcium hydroxide and extrusion conditions completely modified the organized structure of the starch and suggest the formation of a starch-calcium complex (crystalline region). The texture of the extruded products was crispy after puffing. 相似文献
12.
The oil absorption characteristics of a multigrain extruded and fried snack product were studied as a function of extruder screw speed and cooking temperature using a central composite response surface methodology (RSM). The extruded product was produced using a corotating twin screw extruder, dehydrated to a uniform moisture content, and subsequently deep‐fat‐fried at 192 ± 1°C for 10–40 sec to complete expansion. Significant RSM models were developed for oil absorption and extrudate water absorption index (WAI). According to the lowest oil model, absorption (19.9%) was obtained with an extruder screw speed of 218.6 rpm and a cooking temperature of 117.8°C. WAI reached a maximum at a screw speed of 221.9 rpm and a cooking temperature of 109°C. Oil absorption characteristics and extrudate WAI were significantly correlated (r= ‐0.84, P = 0.0002). The data suggest that extrusion conditions can be optimized to influence the physicochemical structures in the extrudate matrix so that oil absorption can be minimized. 相似文献
13.
The effects of extrusion variables (moisture, screw speed, and temperature) and chemicals (urea and sodium bicarbonate) on the properties of starch-based binders (water absorption, bulk density, binder yield, expansion ratio, solubility, pH) and processing conditions (die temperature and pressure, feed rate, and specific mechanical energy) were studied using a central composite design. All quadratic regression models, except the models for bulk density and pH, were significant at the P ≤ 0.06 level. These models can predict the binder properties and processing conditions when extrusion variables and the chemical concentrations are known. Optimum combinations of the chemical concentrations (g/100 g of starch) and extrusion variables to achieve high water absorption in the binders were 15–20 g of urea /100 g of starch, 0–4 g of sodium bicarbonate/100 g of starch, 35–40 g of moisture/100 g of starch, 100–120 rpm screw speed, and 185–215°C barrel temperature. The molecular degradation of the starch occurred during extrusion, especially when the moisture content of starch was <30 g/100 g of starch. 相似文献
14.
Ferouz Y. Ayadi Kasiviswanathan Muthukumarappan Kurt A. Rosentrater Michael L. Brown 《Cereal Chemistry》2011,88(2):179-188
This study was conducted to investigate the production of balanced diets for juvenile yellow perch (Perca flavescens) feeds. Six isocaloric (≈3.21 kcal/g), isonitrogenous (30.1 ± 0.4% db) ingredient blends were formulated with 0, 10, 20, 30, 40, and 50% distillers dried grains with solubles (DDGS), and appropriate amounts of soybean meal, fish meal, vitamins, and minerals. Extrusion cooking was performed using a laboratory‐scale single‐screw extruder at a constant barrel temperature profile of 40–90–100°C, and a constant screw speed of 230 rpm (24.1 rad/sec). The mass flow rate was determined during processing; it generally increased with progressively higher DDGS content. Additionally, moisture content, water activity, unit density, expansion ratio, compressive strength, compressive modulus, pellet durability index, water stability, and color were extensively analyzed to quantify the effects of DDGS content on the physical properties of the resulting extrudates. Significant differences (P < 0.05) between blends were observed for color and water activity for both the raw material and extrudates, respectively, and for the unit density of the extrudates. There were significant changes in brightness (L), redness (a), and yellowness (b) among the final products when increasing the DDGS content of the blends. Expansion ratio and compressive strength of the extrudates were low. On the other hand, all blends showed high pellet durability (PDI ≥ 96.18%). Overall, it was ascertained that DDGS could be successfully included at rates of <50%, and that each of the ingredient blends resulted in viable, high quality extrudates. 相似文献
15.
This study was conducted to develop a ready‐to‐eat extruded food using a single‐screw laboratory extruder. Blends of Indian barley and rice were used as the ingredients for extrusion. The effect of extrusion variables and barley‐to‐rice ratio on properties like expansion ratio, bulk density, water absorption index, hardness, β‐glucan, L*, a*, b* values, and pasting characteristics of extruded products were studied. A central composite rotatable design was used to evaluate the effects of operating variables: die temperature (150–200°C), initial feed moisture content (20–40%), screw speed (90–110 rpm), and barley flour (10–30%) on properties like expansion ratio, bulk density, water absorption index (WAI), hardness, β‐glucan, L*, a*, b* values, and sensory and pasting characteristics of extruded products. Die temperature >175°C and feed moisture <30% resulted in a steep increase in expansion ratio and a decrease in bulk density. Barley flour content of 10% and feed moisture content of <20% resulted in an increased hardness value. When barley flour content was 30–40% and feed moisture content was <20%, a steep increase in the WAI was noticed. Viscosity values of extruded products were far less than those of corresponding unprocessed counterparts as evaluated. Rapid visco analysis indicated that the extruded blend starches were partially pregelatinized as a result of the extrusion process. Sensory scores indicated that barley flour content at 20%, feed moisture content at 30%, and die temperature at 175°C resulted in an acceptable product. The prepared product was roasted in oil using a particular spice mix and its sensory and nutritional properties were studied. 相似文献
16.
《Cereal Chemistry》2017,94(3):385-391
Extrusion expansion characteristics of commercially available whole flours from three green pea varieties (Ariel, Aragorn, and Daytona) and three yellow pea varieties (Carousel, Treasure, and Jetset) were investigated with a corotating twin‐screw extruder. Feed moisture content was kept constant at 15 ± 0.5% (wb). Two barrel temperature levels of 140 and 160°C and three screw speed levels of 150, 200, and 250 rpm were studied. A round die with an opening of 3 mm was used. The radial expansion ratio (ER) of whole pea extrudates was 2.75–3.34. It was shown that the varieties had a significant impact on the expansion properties. Daytona green pea had a significantly greater ER compared with all other varieties (P < 0.05) within the conditions studied. ER was also found to have a positive linear correlation with screw speed. The microstructure of extrudate cross‐sections showed that the samples with greater expansion had more uniform and relatively small pore structure. The results show the importance of using the specific varieties of peas for optimum expansion during extrusion. 相似文献
17.
Extruded pellets were prepared from normal corn starch using a corotating twin‐screw extruder (25:1 L/D ratio, 31 mm diameter screw), and then expanded by heating in a conventional microwave oven for 70 sec. The effects of gelatinization level and moisture content of the extruded pellets on the morphology and physical properties of the microwave‐expanded products such as puffing efficiency, expansion bulk volume, and bulk density were investigated. The expanded shape and air cell structure differed according to the degree of gelatinization of the pellets. Maximum puffing efficiency and expansion volume with the pellets containing 11% moisture were achieved at 52% gelatinization. For this level of gelatinization, starch was extruded at 90°C barrel temperature. In addition, the moisture content of the pellets critically affected the expansion behavior. The maximum puffing efficiency and expansion volume were achieved in a moisture range of 10~13%. For optimum product shape and uniform air cell distribution, the pellets should undergo sudden release of the superheated vapor during the microwave‐heating. The expansion by microwave‐heating was optimized at ≈50% gelatinization. 相似文献
18.
Degermed corn meal adjusted to 18% moisture content (db) with epichlorohydrin (ECH) content at 0, 0.5, 1, or 2% (w/w) were extruded with a twin-screw laboratory extruder at a screw speed of 140 rpm. Compression and metering barrel zones were set at 100, 120, or 140°C. Water solubility (WS) of ground extrudates ranged from 7.6 ± 1.1% to 14.3 ± 1.3%. ECH content had a significant (P < 0.01) negative effect on WS, while barrel temperature and the interaction between barrel temperature and ECH content were not significant (P > 0.05). Presumably, ECH reduced WS of extrudates through cross-linking between hydroxyl groups on starch and protein molecules. Gel-permeation chromatography patterns for both 100 and 140°C barrel temperatures showed that high molecular weight carbohydrates in the extrudates decreased with increasing ECH content without a simultaneous increase in low molecular weight carbohydrates. This suggested that the decrease in high molecular weight fractions was due to insolubilization by cross-linking rather than degradation. SDS-PAGE revealed that two protein bands of ≈29 and 17.5 kDa disappeared, and a new band appeared at 45 kDa with increasing ECH content. This indicated that, most likely, ECH reacted with protein in addition to reacting with starch. However, glycoprotein and starch-protein complexes were not identified with electrophoresis. 相似文献
19.
挤压膨化大米做啤酒辅料的试验研究 总被引：12，自引：4，他引：12
该文通过实验室试验,研究了做啤酒辅料的大米挤压膨化系统诸参数(模孔孔径、套筒温度、物料含水率、螺杆转速),对醪液的主要考察指标(麦汁醪液的总还原糖、过滤速度)的影响规律,指出挤压膨化大米做啤酒辅料的可行性。 相似文献
20.
棉籽粕双螺杆挤压脱毒中几个工艺参数的研究 总被引：1，自引：1，他引：0
利用自行开发的双螺杆食品挤压机对棉籽粕进行挤压脱棉酚试验,考察了含水率、螺杆转速和喂料速度等参数对脱毒效果与挤出产量的影响。实验中采用响应表面法进行实验方案设计和数据分析。结果表明：减低含水率、喂料速度,提高螺杆转速可使脱毒效果改善。喂料速度是影响挤出产量的主要因素。喂料速度越大,产量越大,因而实际中脱毒效果与产量间存在如何均衡的问题。文中相应给出了本实验条件下的几个响应模型,用以评价各加工变量的影响。实验结果还表明本研究所用的双螺杆挤压机的结构参数在棉籽粕挤压脱毒方面是卓有成效的。 相似文献